diff --git a/en_US.ISO8859-1/books/handbook/advanced-networking/chapter.sgml b/en_US.ISO8859-1/books/handbook/advanced-networking/chapter.sgml index b7223be76f..ce442a7b62 100644 --- a/en_US.ISO8859-1/books/handbook/advanced-networking/chapter.sgml +++ b/en_US.ISO8859-1/books/handbook/advanced-networking/chapter.sgml @@ -1,8034 +1,8038 @@ Advanced Networking Synopsis This chapter will cover some of the more frequently used network services on &unix; systems. We will cover how to define, set up, test and maintain all of the network services that FreeBSD utilizes. In addition, there have been example configuration files included throughout this chapter for you to benefit from. After reading this chapter, you will know: The basics of gateways and routes. How to set up IEEE 802.11 and &bluetooth; devices. How to make FreeBSD act as a bridge. How to set up a network filesystem. How to set up network booting on a diskless machine. How to set up a network information server for sharing user accounts. How to set up automatic network settings using DHCP. How to set up a domain name server. How to synchronize the time and date, and set up a time server, with the NTP protocol. How to set up network address translation. How to manage the inetd daemon. How to connect two computers via PLIP. How to set up IPv6 on a FreeBSD machine. How to configure ATM under &os; 5.X. Before reading this chapter, you should: Understand the basics of the /etc/rc scripts. Be familiar with basic network terminology. Coranth Gryphon Contributed by Gateways and Routes routing gateway subnet For one machine to be able to find another over a network, there must be a mechanism in place to describe how to get from one to the other. This is called routing. A route is a defined pair of addresses: a destination and a gateway. The pair indicates that if you are trying to get to this destination, communicate through this gateway. There are three types of destinations: individual hosts, subnets, and default. The default route is used if none of the other routes apply. We will talk a little bit more about default routes later on. There are also three types of gateways: individual hosts, interfaces (also called links), and Ethernet hardware addresses (MAC addresses). An Example To illustrate different aspects of routing, we will use the following example from netstat: &prompt.user; netstat -r Routing tables Destination Gateway Flags Refs Use Netif Expire default outside-gw UGSc 37 418 ppp0 localhost localhost UH 0 181 lo0 test0 0:e0:b5:36:cf:4f UHLW 5 63288 ed0 77 10.20.30.255 link#1 UHLW 1 2421 example.com link#1 UC 0 0 host1 0:e0:a8:37:8:1e UHLW 3 4601 lo0 host2 0:e0:a8:37:8:1e UHLW 0 5 lo0 => host2.example.com link#1 UC 0 0 224 link#1 UC 0 0 default route The first two lines specify the default route (which we will cover in the next section) and the localhost route. loopback device The interface (Netif column) that this routing table specifies to use for localhost is lo0, also known as the loopback device. This says to keep all traffic for this destination internal, rather than sending it out over the LAN, since it will only end up back where it started. Ethernet MAC address The next thing that stands out are the addresses beginning with 0:e0:. These are Ethernet hardware addresses, which are also known as MAC addresses. FreeBSD will automatically identify any hosts (test0 in the example) on the local Ethernet and add a route for that host, directly to it over the Ethernet interface, ed0. There is also a timeout (Expire column) associated with this type of route, which is used if we fail to hear from the host in a specific amount of time. When this happens, the route to this host will be automatically deleted. These hosts are identified using a mechanism known as RIP (Routing Information Protocol), which figures out routes to local hosts based upon a shortest path determination. subnet FreeBSD will also add subnet routes for the local subnet (10.20.30.255 is the broadcast address for the subnet 10.20.30, and example.com is the domain name associated with that subnet). The designation link#1 refers to the first Ethernet card in the machine. You will notice no additional interface is specified for those. Both of these groups (local network hosts and local subnets) have their routes automatically configured by a daemon called routed. If this is not run, then only routes which are statically defined (i.e. entered explicitly) will exist. The host1 line refers to our host, which it knows by Ethernet address. Since we are the sending host, FreeBSD knows to use the loopback interface (lo0) rather than sending it out over the Ethernet interface. The two host2 lines are an example of what happens when we use an &man.ifconfig.8; alias (see the section on Ethernet for reasons why we would do this). The => symbol after the lo0 interface says that not only are we using the loopback (since this address also refers to the local host), but specifically it is an alias. Such routes only show up on the host that supports the alias; all other hosts on the local network will simply have a link#1 line for such routes. The final line (destination subnet 224) deals with multicasting, which will be covered in another section. Finally, various attributes of each route can be seen in the Flags column. Below is a short table of some of these flags and their meanings: U Up: The route is active. H Host: The route destination is a single host. G Gateway: Send anything for this destination on to this remote system, which will figure out from there where to send it. S Static: This route was configured manually, not automatically generated by the system. C Clone: Generates a new route based upon this route for machines we connect to. This type of route is normally used for local networks. W WasCloned: Indicated a route that was auto-configured based upon a local area network (Clone) route. L Link: Route involves references to Ethernet hardware. Default Routes default route When the local system needs to make a connection to a remote host, it checks the routing table to determine if a known path exists. If the remote host falls into a subnet that we know how to reach (Cloned routes), then the system checks to see if it can connect along that interface. If all known paths fail, the system has one last option: the default route. This route is a special type of gateway route (usually the only one present in the system), and is always marked with a c in the flags field. For hosts on a local area network, this gateway is set to whatever machine has a direct connection to the outside world (whether via PPP link, DSL, cable modem, T1, or another network interface). If you are configuring the default route for a machine which itself is functioning as the gateway to the outside world, then the default route will be the gateway machine at your Internet Service Provider's (ISP) site. Let us look at an example of default routes. This is a common configuration: [Local2] <--ether--> [Local1] <--PPP--> [ISP-Serv] <--ether--> [T1-GW] The hosts Local1 and Local2 are at your site. Local1 is connected to an ISP via a dial up PPP connection. This PPP server computer is connected through a local area network to another gateway computer through an external interface to the ISPs Internet feed. The default routes for each of your machines will be: Host Default Gateway Interface Local2 Local1 Ethernet Local1 T1-GW PPP A common question is Why (or how) would we set the T1-GW to be the default gateway for Local1, rather than the ISP server it is connected to?. Remember, since the PPP interface is using an address on the ISP's local network for your side of the connection, routes for any other machines on the ISP's local network will be automatically generated. Hence, you will already know how to reach the T1-GW machine, so there is no need for the intermediate step of sending traffic to the ISP server. It is common to use the address X.X.X.1 as the gateway address for your local network. So (using the same example), if your local class-C address space was 10.20.30 and your ISP was using 10.9.9 then the default routes would be: Host Default Route Local2 (10.20.30.2) Local1 (10.20.30.1) Local1 (10.20.30.1, 10.9.9.30) T1-GW (10.9.9.1) You can easily define the default route via the /etc/rc.conf file. In our example, on the Local2 machine, we added the following line in /etc/rc.conf: defaultrouter="10.20.30.1" It is also possible to do it directly from the command line with the &man.route.8; command: &prompt.root; route add default 10.20.30.1 For more informations on manual manipulation of network routing tables, consult &man.route.8; manual page. Dual Homed Hosts dual homed hosts There is one other type of configuration that we should cover, and that is a host that sits on two different networks. Technically, any machine functioning as a gateway (in the example above, using a PPP connection) counts as a dual-homed host. But the term is really only used to refer to a machine that sits on two local-area networks. In one case, the machine has two Ethernet cards, each having an address on the separate subnets. Alternately, the machine may only have one Ethernet card, and be using &man.ifconfig.8; aliasing. The former is used if two physically separate Ethernet networks are in use, the latter if there is one physical network segment, but two logically separate subnets. Either way, routing tables are set up so that each subnet knows that this machine is the defined gateway (inbound route) to the other subnet. This configuration, with the machine acting as a router between the two subnets, is often used when we need to implement packet filtering or firewall security in either or both directions. If you want this machine to actually forward packets between the two interfaces, you need to tell FreeBSD to enable this ability. See the next section for more details on how to do this. Building a Router router A network router is simply a system that forwards packets from one interface to another. Internet standards and good engineering practice prevent the FreeBSD Project from enabling this by default in FreeBSD. You can enable this feature by changing the following variable to YES in &man.rc.conf.5;: gateway_enable=YES # Set to YES if this host will be a gateway This option will set the &man.sysctl.8; variable net.inet.ip.forwarding to 1. If you should need to stop routing temporarily, you can reset this to 0 temporarily. Your new router will need routes to know where to send the traffic. If your network is simple enough you can use static routes. FreeBSD also comes with the standard BSD routing daemon &man.routed.8;, which speaks RIP (both version 1 and version 2) and IRDP. Support for BGP v4, OSPF v2, and other sophisticated routing protocols is available with the net/zebra package. Commercial products such as &gated; are also available for more complex network routing solutions. BGP RIP OSPF Even when FreeBSD is configured in this way, it does not completely comply with the Internet standard requirements for routers. It comes close enough for ordinary use, however. Al Hoang Contributed by Setting Up Static Routes Manual Configuration Let us assume we have a network as follows: INTERNET | (10.0.0.1/24) Default Router to Internet | |Interface xl0 |10.0.0.10/24 +------+ | | RouterA | | (FreeBSD gateway) +------+ | Interface xl1 | 192.168.1.1/24 | +--------------------------------+ Internal Net 1 | 192.168.1.2/24 | +------+ | | RouterB | | +------+ | 192.168.2.1/24 | Internal Net 2 In this scenario, RouterA is our &os; machine that is acting as a router to the rest of the Internet. It has a default route set to 10.0.0.1 which allows it to connect with the outside world. We will assume that RouterB is already configured properly and knows how to get wherever it needs to go. (This is simple in this picture. Just add a default route on RouterB using 192.168.1.1 as the gateway.) If we look at the routing table for RouterA we would see something like the following: &prompt.user; netstat -nr Routing tables Internet: Destination Gateway Flags Refs Use Netif Expire default 10.0.0.1 UGS 0 49378 xl0 127.0.0.1 127.0.0.1 UH 0 6 lo0 10.0.0/24 link#1 UC 0 0 xl0 192.168.1/24 link#2 UC 0 0 xl1 With the current routing table RouterA will not be able to reach our Internal Net 2. It does not have a route for 192.168.2.0/24. One way to alleviate this is to manually add the route. The following command would add the Internal Net 2 network to RouterA's routing table using 192.168.1.2 as the next hop: &prompt.root; route add -net 192.168.2.0/24 192.168.1.2 Now RouterA can reach any hosts on the 192.168.2.0/24 network. Persistent Configuration The above example is perfect for configuring a static route on a running system. However, one problem is that the routing information will not persist if you reboot your &os; machine. The way to handle the addition of a static route is to put it in your /etc/rc.conf file: # Add Internal Net 2 as a static route static_routes="internalnet2" route_internalnet2="-net 192.168.2.0/24 192.168.1.2" The static_routes configuration variable is a list of strings seperated by a space. Each string references to a route name. In our above example we only have one string in static_routes. This string is internalnet2. We then add a configuration variable called route_internalnet2 where we put all of the configuration parameters we would give to the &man.route.8; command. For our example above we would have used the command: &prompt.root; route add -net 192.168.2.0/24 192.168.1.2 so we need "-net 192.168.2.0/24 192.168.1.2". As said above, we can have more than one string in static_routes. This allows us to create multiple static routes. The following lines shows an example of adding static routes for the 192.168.0.0/24 and 192.168.1.0/24 networks on an imaginary router: static_routes="net1 net2" route_net1="-net 192.168.0.0/24 192.168.0.1" route_net2="-net 192.168.1.0/24 192.168.1.1" Routing Propagation routing propagation We have already talked about how we define our routes to the outside world, but not about how the outside world finds us. We already know that routing tables can be set up so that all traffic for a particular address space (in our examples, a class-C subnet) can be sent to a particular host on that network, which will forward the packets inbound. When you get an address space assigned to your site, your service provider will set up their routing tables so that all traffic for your subnet will be sent down your PPP link to your site. But how do sites across the country know to send to your ISP? There is a system (much like the distributed DNS information) that keeps track of all assigned address-spaces, and defines their point of connection to the Internet Backbone. The Backbone are the main trunk lines that carry Internet traffic across the country, and around the world. Each backbone machine has a copy of a master set of tables, which direct traffic for a particular network to a specific backbone carrier, and from there down the chain of service providers until it reaches your network. It is the task of your service provider to advertise to the backbone sites that they are the point of connection (and thus the path inward) for your site. This is known as route propagation. Troubleshooting traceroute Sometimes, there is a problem with routing propagation, and some sites are unable to connect to you. Perhaps the most useful command for trying to figure out where routing is breaking down is the &man.traceroute.8; command. It is equally useful if you cannot seem to make a connection to a remote machine (i.e. &man.ping.8; fails). The &man.traceroute.8; command is run with the name of the remote host you are trying to connect to. It will show the gateway hosts along the path of the attempt, eventually either reaching the target host, or terminating because of a lack of connection. For more information, see the manual page for &man.traceroute.8;. Multicast Routing multicast options MROUTING FreeBSD supports both multicast applications and multicast routing natively. Multicast applications do not require any special configuration of FreeBSD; applications will generally run out of the box. Multicast routing requires that support be compiled into the kernel: options MROUTING In addition, the multicast routing daemon, &man.mrouted.8; must be configured to set up tunnels and DVMRP via /etc/mrouted.conf. More details on multicast configuration may be found in the manual page for &man.mrouted.8;. Eric Anderson Written by Wireless Networking wireless networking 802.11 wireless networking Introduction It can be very useful to be able to use a computer without the annoyance of having a network cable attached at all times. FreeBSD can be used as a wireless client, and even as a wireless access point. Wireless Modes of Operation There are two different ways to configure 802.11 wireless devices: BSS and IBSS. BSS Mode BSS mode is the mode that typically is used. BSS mode is also called infrastructure mode. In this mode, a number of wireless access points are connected to a wired network. Each wireless network has its own name. This name is called the SSID of the network. Wireless clients connect to these wireless access points. The IEEE 802.11 standard defines the protocol that wireless networks use to connect. A wireless client can be tied to a specific network, when a SSID is set. A wireless client can also attach to any network by not explicitly setting a SSID. IBSS Mode IBSS mode, also called ad-hoc mode, is designed for point to point connections. There are actually two types of ad-hoc mode. One is IBSS mode, also called ad-hoc or IEEE ad-hoc mode. This mode is defined by the IEEE 802.11 standards. The second is called demo ad-hoc mode or Lucent ad-hoc mode (and sometimes, confusingly, ad-hoc mode). This is the old, pre-802.11 ad-hoc mode and should only be used for legacy installations. We will not cover either of the ad-hoc modes further. Infrastructure Mode Access Points Access points are wireless networking devices that allow one or more wireless clients to use the device as a central hub. When using an access point, all clients communicate through the access point. Multiple access points are often used to cover a complete area such as a house, business, or park with a wireless network. Access points typically have multiple network connections: the wireless card, and one or more wired Ethernet adapters for connection to the rest of the network. Access points can either be purchased prebuilt, or you can build your own with FreeBSD and a supported wireless card. Several vendors make wireless access points and wireless cards with various features. Building a FreeBSD Access Point wireless networking access point Requirements In order to set up a wireless access point with FreeBSD, you need to have a compatible wireless card. Currently, only cards with the Prism chipset are supported. You will also need a wired network card that is supported by FreeBSD (this should not be difficult to find, FreeBSD supports a lot of different devices). For this guide, we will assume you want to &man.bridge.4; all traffic between the wireless device and the network attached to the wired network card. The hostap functionality that FreeBSD uses to implement the access point works best with certain versions of firmware. Prism 2 cards should use firmware version 1.3.4 or newer. Prism 2.5 and Prism 3 cards should use firmware 1.4.9. Older versions of the firmware way or may not function correctly. At this time, the only way to update cards is with &windows; firmware update utilities available from your card's manufacturer. Setting It Up First, make sure your system can see the wireless card: &prompt.root; ifconfig -a wi0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 inet6 fe80::202:2dff:fe2d:c938%wi0 prefixlen 64 scopeid 0x7 inet 0.0.0.0 netmask 0xff000000 broadcast 255.255.255.255 ether 00:09:2d:2d:c9:50 media: IEEE 802.11 Wireless Ethernet autoselect (DS/2Mbps) status: no carrier ssid "" stationname "FreeBSD Wireless node" channel 10 authmode OPEN powersavemode OFF powersavesleep 100 wepmode OFF weptxkey 1 Do not worry about the details now, just make sure it shows you something to indicate you have a wireless card installed. If you have trouble seeing the wireless interface, and you are using a PC Card, you may want to check out &man.pccardc.8; and &man.pccardd.8; manual pages for more information. Next, you will need to load a module in order to get the bridging part of FreeBSD ready for the access point. To load the &man.bridge.4; module, simply run the following command: &prompt.root; kldload bridge It should not have produced any errors when loading the module. If it did, you may need to compile the &man.bridge.4; code into your kernel. The Bridging section of this handbook should be able to help you accomplish that task. Now that you have the bridging stuff done, we need to tell the FreeBSD kernel which interfaces to bridge together. We do that by using &man.sysctl.8;: &prompt.root; sysctl net.link.ether.bridge=1 &prompt.root; sysctl net.link.ether.bridge_cfg="wi0,xl0" &prompt.root; sysctl net.inet.ip.forwarding=1 On &os; 5.2-RELEASE and later, you have to use instead the following options: &prompt.root; sysctl net.link.ether.bridge.enable=1 &prompt.root; sysctl net.link.ether.bridge.config="wi0,xl0" &prompt.root; sysctl net.inet.ip.forwarding=1 Now it is time for the wireless card setup. The following command will set the card into an access point: &prompt.root; ifconfig wi0 ssid my_net channel 11 media DS/11Mbps mediaopt hostap up stationname "FreeBSD AP" The &man.ifconfig.8; line brings the wi0 interface up, sets its SSID to my_net, and sets the station name to FreeBSD AP. The sets the card into 11Mbps mode and is needed for any to take effect. The option places the interface into access point mode. The option sets the 802.11b channel to use. The &man.wicontrol.8; manual page has valid channel options for your regulatory domain. Now you should have a complete functioning access point up and running. You are encouraged to read &man.wicontrol.8;, &man.ifconfig.8;, and &man.wi.4; for further information. It is also suggested that you read the section on encryption that follows. Status Information Once the access point is configured and operational, operators will want to see the clients that are associated with the access point. At any time, the operator may type: &prompt.root; wicontrol -l 1 station: 00:09:b7:7b:9d:16 asid=04c0, flags=3<ASSOC,AUTH>, caps=1<ESS>, rates=f<1M,2M,5.5M,11M>, sig=38/15 This shows that there is one station associated, along with its parameters. The signal indicated should be used as a relative indication of strength only. Its translation to dBm or other units varies between different firmware revisions. Clients A wireless client is a system that accesses an access point or another client directly. Typically, wireless clients only have one network device, the wireless networking card. There are a few different ways to configure a wireless client. These are based on the different wireless modes, generally BSS (infrastructure mode, which requires an access point), and IBSS (ad-hoc, or peer-to-peer mode). In our example, we will use the most popular of the two, BSS mode, to talk to an access point. Requirements There is only one real requirement for setting up FreeBSD as a wireless client. You will need a wireless card that is supported by FreeBSD. Setting Up a Wireless FreeBSD Client You will need to know a few things about the wireless network you are joining before you start. In this example, we are joining a network that has a name of my_net, and encryption turned off. In this example, we are not using encryption, which is a dangerous situation. In the next section, you will learn how to turn on encryption, why it is important to do so, and why some encryption technologies still do not completely protect you. Make sure your card is recognized by FreeBSD: &prompt.root; ifconfig -a wi0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 inet6 fe80::202:2dff:fe2d:c938%wi0 prefixlen 64 scopeid 0x7 inet 0.0.0.0 netmask 0xff000000 broadcast 255.255.255.255 ether 00:09:2d:2d:c9:50 media: IEEE 802.11 Wireless Ethernet autoselect (DS/2Mbps) status: no carrier ssid "" stationname "FreeBSD Wireless node" channel 10 authmode OPEN powersavemode OFF powersavesleep 100 wepmode OFF weptxkey 1 Now, we can set the card to the correct settings for our network: &prompt.root; ifconfig wi0 inet 192.168.0.20 netmask 255.255.255.0 ssid my_net Replace 192.168.0.20 and 255.255.255.0 with a valid IP address and netmask on your wired network. Remember, our access point is bridging the data between the wireless network, and the wired network, so it will appear to the other devices on your network that you are on the wired network just as they are. Once you have done that, you should be able to ping hosts on the wired network just as if you were connected using a standard wired connection. If you are experiencing problems with your wireless connection, check to make sure that your are associated (connected) to the access point: &prompt.root; ifconfig wi0 should return some information, and you should see: status: associated If it does not show associated, then you may be out of range of the access point, have encryption on, or possibly have a configuration problem. Encryption wireless networking encryption Encryption on a wireless network is important because you no longer have the ability to keep the network contained in a well protected area. Your wireless data will be broadcast across your entire neighborhood, so anyone who cares to read it can. This is where encryption comes in. By encrypting the data that is sent over the airwaves, you make it much more difficult for any interested party to grab your data right out of the air. The two most common ways to encrypt the data between your client and the access point are WEP, and &man.ipsec.4;. WEP WEP WEP is an abbreviation for Wired Equivalency Protocol. WEP is an attempt to make wireless networks as safe and secure as a wired network. Unfortunately, it has been cracked, and is fairly trivial to break. This also means it is not something to rely on when it comes to encrypting sensitive data. It is better than nothing, so use the following to turn on WEP on your new FreeBSD access point: &prompt.root; ifconfig wi0 inet up ssid my_net wepmode on wepkey 0x1234567890 media DS/11Mbps mediaopt hostap And you can turn on WEP on a client with this command: &prompt.root; ifconfig wi0 inet 192.168.0.20 netmask 255.255.255.0 ssid my_net wepmode on wepkey 0x1234567890 Note that you should replace the 0x1234567890 with a more unique key. IPsec &man.ipsec.4; is a much more robust and powerful tool for encrypting data across a network. This is definitely the preferred way to encrypt data over a wireless network. You can read more about &man.ipsec.4; security and how to implement it in the IPsec section of this handbook. Tools There are a small number of tools available for use in debugging and setting up your wireless network, and here we will attempt to describe some of them and what they do. The <application>bsd-airtools</application> Package The bsd-airtools package is a complete toolset that includes wireless auditing tools for WEP key cracking, access point detection, etc. The bsd-airtools utilities can be installed from the net/bsd-airtools port. Information on installing ports can be found in of this handbook. The program dstumbler is the packaged tool that allows for access point discovery and signal to noise ratio graphing. If you are having a hard time getting your access point up and running, dstumbler may help you get started. To test your wireless network security, you may choose to use dweputils (dwepcrack, dwepdump and dwepkeygen) to help you determine if WEP is the right solution to your wireless security needs. The <command>wicontrol</command>, <command>ancontrol</command> and <command>raycontrol</command> Utilities These are the tools you can use to control how your wireless card behaves on the wireless network. In the examples above, we have chosen to use &man.wicontrol.8;, since our wireless card is a wi0 interface. If you had a Cisco wireless device, it would come up as an0, and therefore you would use &man.ancontrol.8;. The <command>ifconfig</command> Command ifconfig The &man.ifconfig.8; command can be used to do many of the same options as &man.wicontrol.8;, however it does lack a few options. Check &man.ifconfig.8; for command line parameters and options. Supported Cards Access Points The only cards that are currently supported for BSS (as an access point) mode are devices based on the Prism 2, 2.5, or 3 chipsets. For a complete list, look at &man.wi.4;. Clients Almost all 802.11b wireless cards are currently supported under FreeBSD. Most cards based on Prism, Spectrum24, Hermes, Aironet, and Raylink will work as a wireless network card in IBSS (ad-hoc, peer-to-peer, and BSS) mode. Pav Lucistnik Written by
pav@oook.cz
 Bluetooth Bluetooth Introduction Bluetooth is a wireless technology for creating personal networks operating in the 2.4 GHz unlicensed band, with a range of 10 meters. Networks are usually formed ad-hoc from portable devices such as cellular phones, handhelds and laptops. Unlike the other popular wireless technology, Wi-Fi, Bluetooth offers higher level service profiles, e.g. FTP-like file servers, file pushing, voice transport, serial line emulation, and more. The Bluetooth stack in &os; is implemented using the Netgraph framework (see &man.netgraph.4;). A broad variety of Bluetooth USB dongles is supported by the &man.ng.ubt.4; driver. The Broadcom BCM2033 chip based Bluetooth devices are supported via the &man.ubtbcmfw.4; and &man.ng.ubt.4; drivers. The 3Com Bluetooth PC Card 3CRWB60-A is supported by the &man.ng.bt3c.4; driver. Serial and UART based Bluetooth devices are supported via &man.sio.4;, &man.ng.h4.4; and &man.hcseriald.8;. This chapter describes the use of the USB Bluetooth dongle. Bluetooth support is available in &os; 5.0 and newer systems. Plugging in the Device By default Bluetooth device drivers are available as kernel modules. Before attaching a device, you will need to load the driver into the kernel. &prompt.root; kldload ng_ubt If the Bluetooth device is present in the system during system startup, load the module from /boot/loader.conf. ng_ubt_load="YES" Plug in your USB dongle. The output similar to the following will appear on the console (or in syslog). ubt0: vendor 0x0a12 product 0x0001, rev 1.10/5.25, addr 2 ubt0: Interface 0 endpoints: interrupt=0x81, bulk-in=0x82, bulk-out=0x2 ubt0: Interface 1 (alt.config 5) endpoints: isoc-in=0x83, isoc-out=0x3, wMaxPacketSize=49, nframes=6, buffer size=294 Copy /usr/share/examples/netgraph/bluetooth/rc.bluetooth into some convenient place, like /etc/rc.bluetooth. This script is used to start and stop the Bluetooth stack. It is a good idea to stop the stack before unplugging the device, but it is not (usually) fatal. When starting the stack, you will receive output similar to the following: &prompt.root; /etc/rc.bluetooth start ubt0 BD_ADDR: 00:02:72:00:d4:1a Features: 0xff 0xff 0xf 00 00 00 00 00 <3-Slot> <5-Slot> <Encryption> <Slot offset> <Timing accuracy> <Switch> <Hold mode> <Sniff mode> <Park mode> <RSSI> <Channel quality> <SCO link> <HV2 packets> <HV3 packets> <u-law log> <A-law log> <CVSD> <Paging scheme> <Power control> <Transparent SCO data> Max. ACL packet size: 192 bytes Number of ACL packets: 8 Max. SCO packet size: 64 bytes Number of SCO packets: 8 HCI Host Controller Interface (HCI) Host Controller Interface (HCI) provides a command interface to the baseband controller and link manager, and access to hardware status and control registers. This interface provides a uniform method of accessing the Bluetooth baseband capabilities. HCI layer on the Host exchanges data and commands with the HCI firmware on the Bluetooth hardware. The Host Controller Transport Layer (i.e. physical bus) driver provides both HCI layers with the ability to exchange information with each other. A single Netgraph node of type hci is created for a single Bluetooth device. The HCI node is normally connected to the Bluetooth device driver node (downstream) and the L2CAP node (upstream). All HCI operations must be performed on the HCI node and not on the device driver node. Default name for the HCI node is devicehci. For more details refer to the &man.ng.hci.4; man page. One of the most common tasks is discovery of Bluetooth devices in RF proximity. This operation is called inquiry. Inquiry and other HCI realated operations are done with the &man.hccontrol.8; utility. The example below shows how to find out which Bluetooth devices are in range. You should receive the list of devices in a few seconds. Note that a remote device will only answer the inquiry if it put into discoverable mode. &prompt.user; hccontrol -n ubt0hci inquiry Inquiry result, num_responses=1 Inquiry result #0 BD_ADDR: 00:80:37:29:19:a4 Page Scan Rep. Mode: 0x1 Page Scan Period Mode: 00 Page Scan Mode: 00 Class: 52:02:04 Clock offset: 0x78ef Inquiry complete. Status: No error [00] BD_ADDR is unique address of a Bluetooth device, similar to MAC addresses of a network card. This address is needed for further communication with a device. It is possible to assign human readable name to a BD_ADDR. The /etc/bluetooth/hosts file contains information regarding the known Bluetooth hosts. The following example shows how to obtain human readable name that was assigned to the remote device. &prompt.user; hccontrol -n ubt0hci remote_name_request 00:80:37:29:19:a4 BD_ADDR: 00:80:37:29:19:a4 Name: Pav's T39 If you perform an inquiry on a remote Bluetooth device, it will find your computer as your.host.name (ubt0). The name assigned to the local device can be changed at any time. The Bluetooth system provides a point-to-point connection (only two Bluetooth units involved), or a point-to-multipoint connection. In the point-to-multipoint connection the connection is shared among several Bluetooth devices. The following example shows how to obtain the list of active baseband connections for the local device. &prompt.user; hccontrol -n ubt0hci read_connection_list Remote BD_ADDR Handle Type Mode Role Encrypt Pending Queue State 00:80:37:29:19:a4 41 ACL 0 MAST NONE 0 0 OPEN A connection handle is useful when termination of the baseband connection is required. Note, that it is normally not required to do it by hand. The stack will automatically terminate inactive baseband connections. &prompt.root; hccontrol -n ubt0hci disconnect 41 Connection handle: 41 Reason: Connection terminated by local host [0x16] Refer to hccontrol help for a complete listing of available HCI commands. Most of the HCI commands do not require superuser privileges. L2CAP Logical Link Control and Adaptation Protocol (L2CAP) Logical Link Control and Adaptation Protocol (L2CAP) provides connection-oriented and connectionless data services to upper layer protocols with protocol multiplexing capability and segmentation and reassembly operation. L2CAP permits higher level protocols and applications to transmit and receive L2CAP data packets up to 64 kilobytes in length. L2CAP is based around the concept of channels. Channel is a logical connection on top of baseband connection. Each channel is bound to a single protocol in a many-to-one fashion. Multiple channels can be bound to the same protocol, but a channel cannot be bound to multiple protocols. Each L2CAP packet received on a channel is directed to the appropriate higher level protocol. Multiple channels can share the same baseband connection. A single Netgraph node of type l2cap is created for a single Bluetooth device. The L2CAP node is normally connected to the Bluetooth HCI node (downstream) and Bluetooth sockets nodes (upstream). Default name for the L2CAP node is devicel2cap. For more details refer to the &man.ng.l2cap.4; man page. A useful command is &man.l2ping.8;, which can be used to ping other devices. Some Bluetooth implementations might not return all of the data sent to them, so 0 bytes in the following example is normal. &prompt.root; l2ping -a 00:80:37:29:19:a4 0 bytes from 0:80:37:29:19:a4 seq_no=0 time=48.633 ms result=0 0 bytes from 0:80:37:29:19:a4 seq_no=1 time=37.551 ms result=0 0 bytes from 0:80:37:29:19:a4 seq_no=2 time=28.324 ms result=0 0 bytes from 0:80:37:29:19:a4 seq_no=3 time=46.150 ms result=0 The &man.l2control.8; utility is used to perform various operations on L2CAP nodes. This example shows how to obtain the list of logical connections (channels) and the list of baseband connections for the local device. &prompt.user; l2control -a 00:02:72:00:d4:1a read_channel_list L2CAP channels: Remote BD_ADDR SCID/ DCID PSM IMTU/ OMTU State 00:07:e0:00:0b:ca 66/ 64 3 132/ 672 OPEN &prompt.user; l2control -a 00:02:72:00:d4:1a read_connection_list L2CAP connections: Remote BD_ADDR Handle Flags Pending State 00:07:e0:00:0b:ca 41 O 0 OPEN Another diagnostic tool is &man.btsockstat.1;. It does a job similar to as &man.netstat.1; does, but for Bluetooth network-related data structures. The example below shows the same logical connection as &man.l2control.8; above. &prompt.user; btsockstat Active L2CAP sockets PCB Recv-Q Send-Q Local address/PSM Foreign address CID State c2afe900 0 0 00:02:72:00:d4:1a/3 00:07:e0:00:0b:ca 66 OPEN Active RFCOMM sessions L2PCB PCB Flag MTU Out-Q DLCs State c2afe900 c2b53380 1 127 0 Yes OPEN Active RFCOMM sockets PCB Recv-Q Send-Q Local address Foreign address Chan DLCI State c2e8bc80 0 250 00:02:72:00:d4:1a 00:07:e0:00:0b:ca 3 6 OPEN RFCOMM RFCOMM Protocol The RFCOMM protocol provides emulation of serial ports over the L2CAP protocol. The protocol is based on the ETSI standard TS 07.10. RFCOMM is a simple transport protocol, with additional provisions for emulating the 9 circuits of RS-232 (EIATIA-232-E) serial ports. The RFCOMM protocol supports up to 60 simultaneous connections (RFCOMM channels) between two Bluetooth devices. For the purposes of RFCOMM, a complete communication path involves two applications running on different devices (the communication endpoints) with a communication segment between them. RFCOMM is intended to cover applications that make use of the serial ports of the devices in which they reside. The communication segment is a Bluetooth link from one device to another (direct connect). RFCOMM is only concerned with the connection between the devices in the direct connect case, or between the device and a modem in the network case. RFCOMM can support other configurations, such as modules that communicate via Bluetooth wireless technology on one side and provide a wired interface on the other side. In &os; the RFCOMM protocol is implemented at the Bluetooth sockets layer. pairing Pairing of Devices By default, Bluetooth communication is not authenticated, and any device can talk to any other device. A Bluetooth device (for example, cellular phone) may choose to require authentication to provide a particular service (for example, Dial-Up service). Bluetooth authentication is normally done with PIN codes. A PIN code is an ASCII string up to 16 characters in length. User is required to enter the same PIN code on both devices. Once user has entered the PIN code, both devices will generate a link key. After that the link key can be stored either in the devices themselves or in a persistent storage. Next time both devices will use previously generated link key. The described above procedure is called pairing. Note that if the link key is lost by any device then pairing must be repeated. The &man.hcsecd.8; daemon is responsible for handling of all Bluetooth authentication requests. The default configuration file is /etc/bluetooth/hcsecd.conf. An example section for a cellular phone with the PIN code arbitrarily set to 1234 is shown below. device { bdaddr 00:80:37:29:19:a4; name "Pav's T39"; key nokey; pin "1234"; } There is no limitation on PIN codes (except length). Some devices (for example Bluetooth headsets) may have a fixed PIN code built in. The switch forces the &man.hcsecd.8; daemon to stay in the foreground, so it is easy to see what is happening. Set the remote device to receive pairing and initiate the Bluetooth connection to the remote device. The remote device should say that pairing was accepted, and request the PIN code. Enter the same PIN code as you have in hcsecd.conf. Now your PC and the remote device are paired. Alternatively, you can initiate pairing on the remote device. Below in the sample hcsecd output. hcsecd[16484]: Got Link_Key_Request event from 'ubt0hci', remote bdaddr 0:80:37:29:19:a4 hcsecd[16484]: Found matching entry, remote bdaddr 0:80:37:29:19:a4, name 'Pav's T39', link key doesn't exist hcsecd[16484]: Sending Link_Key_Negative_Reply to 'ubt0hci' for remote bdaddr 0:80:37:29:19:a4 hcsecd[16484]: Got PIN_Code_Request event from 'ubt0hci', remote bdaddr 0:80:37:29:19:a4 hcsecd[16484]: Found matching entry, remote bdaddr 0:80:37:29:19:a4, name 'Pav's T39', PIN code exists hcsecd[16484]: Sending PIN_Code_Reply to 'ubt0hci' for remote bdaddr 0:80:37:29:19:a4 SDP Service Discovery Protocol (SDP) The Service Discovery Protocol (SDP) provides the means for client applications to discover the existence of services provided by server applications as well as the attributes of those services. The attributes of a service include the type or class of service offered and the mechanism or protocol information needed to utilize the service. SDP involves communication between a SDP server and a SDP client. The server maintains a list of service records that describe the characteristics of services associated with the server. Each service record contains information about a single service. A client may retrieve information from a service record maintained by the SDP server by issuing a SDP request. If the client, or an application associated with the client, decides to use a service, it must open a separate connection to the service provider in order to utilize the service. SDP provides a mechanism for discovering services and their attributes, but it does not provide a mechanism for utilizing those services. Normally, a SDP client searches for services based on some desired characteristics of the services. However, there are times when it is desirable to discover which types of services are described by an SDP server's service records without any a priori information about the services. This process of looking for any offered services is called browsing. The Bluetooth SDP server &man.sdpd.8; and command line client &man.sdpcontrol.8; are included in the standard &os; installation. The following example shows how to perform a SDP browse query. &prompt.user; sdpcontrol -a 00:01:03:fc:6e:ec browse Record Handle: 00000000 Service Class ID List: Service Discovery Server (0x1000) Protocol Descriptor List: L2CAP (0x0100) Protocol specific parameter #1: u/int/uuid16 1 Protocol specific parameter #2: u/int/uuid16 1 Record Handle: 0x00000001 Service Class ID List: Browse Group Descriptor (0x1001) Record Handle: 0x00000002 Service Class ID List: LAN Access Using PPP (0x1102) Protocol Descriptor List: L2CAP (0x0100) RFCOMM (0x0003) Protocol specific parameter #1: u/int8/bool 1 Bluetooth Profile Descriptor List: LAN Access Using PPP (0x1102) ver. 1.0 ... and so on. Note that each service has a list of attributes (RFCOMM channel for example). Depending on the service you might need to make a note of some of the attributes. Some Bluetooth implementations do not support service browsing and may return an empty list. In this case it is possible to search for the specific service. The example below shows how to search for the OBEX Object Push (OPUSH) service. &prompt.user; sdpcontrol -a 00:01:03:fc:6e:ec search OPUSH Offering services on &os; to Bluetooth clients is done with the &man.sdpd.8; server. &prompt.root; sdpd The local server application that wants to provide Bluetooth service to the remote clients will register service with the local SDP daemon. The example of such application is &man.rfcomm.pppd.8;. Once started it will register Bluetooth LAN service with the local SDP daemon. The list of services registered with the local SDP server can be obtained by issuing SDP browse query via local control channel. &prompt.root; sdpcontrol -l browse Dial-Up Networking (DUN) and Network Access with PPP (LAN) Profiles The Dial-Up Networking (DUN) profile is mostly used with modems and cellular phones. The scenarios covered by this profile are the following: use of a cellular phone or modem by a computer as a wireless modem for connecting to a dial-up internet access server, or using other dial-up services; use of a cellular phone or modem by a computer to receive data calls. Network Access with PPP (LAN) profile can be used in the following situations: LAN access for a single Bluetooth device; LAN access for multiple Bluetooth devices; PC to PC (using PPP networking over serial cable emulation). In &os; both profiles are implemented with &man.ppp.8; and &man.rfcomm.pppd.8; - a wrapper that converts RFCOMM Bluetooth connection into something PPP can operate with. Before any profile can be used, a new PPP label in the /etc/ppp/ppp.conf must be created. Consult &man.rfcomm.pppd.8; manual page for examples. In the following example &man.rfcomm.pppd.8; will be used to open RFCOMM connection to remote device with BD_ADDR 00:80:37:29:19:a4 on DUN RFCOMM channel. The actual RFCOMM channel number will be obtained from the remote device via SDP. It is possible to specify RFCOMM channel by hand, and in this case &man.rfcomm.pppd.8; will not perform SDP query. Use &man.sdpcontrol.8; to find out RFCOMM channel on the remote device. &prompt.root; rfcomm_pppd -a 00:80:37:29:19:a4 -c -C dun -l rfcomm-dialup In order to provide Network Access with PPP (LAN) service the &man.sdpd.8; server must be running. A new entry for LAN clients must be created in the /etc/ppp/ppp.conf file. Consult &man.rfcomm.pppd.8; manual page for examples. Finally, start RFCOMM PPP server on valid RFCOMM channel number. The RFCOMM PPP server will automatically register Bluetooth LAN service with the local SDP daemon. The example below shows how to start RFCOMM PPP server. &prompt.root; rfcomm_pppd -s -C 7 -l rfcomm-server OBEX OBEX Object Push (OPUSH) Profile OBEX is a widely used protocol for simple file transfers between mobile devices. Its main use is in infrared communication, where it is used for generic file transfers between notebooks or Palm handhelds, and for sending business cards or calendar entries between cellular phones and other devices with PIM applications. The OBEX server and client are implemented as a third-party package obexapp-1.2 that can be downloaded from here. The package requires the openobex-1.0.1 library (included) and the devel/gmake port. OBEX client is used to push and/or pull objects from the OBEX server. An object can, for example, be a business card or an appointment. The OBEX client can obtain RFCOMM channel number from the remote device via SDP. This can be done by specifying service name instead of RFCOMM channel number. Supported service names are: IrMC, FTRN and OPUSH. It is possible to specify RFCOMM channel as a number. Below is an example of an OBEX session, where device information object is pulled from the cellular phone, and a new object (business card) is pushed into the phone's directory. &prompt.user; obexapp -a 00:80:37:29:19:a4 -C IrMC obex> get get: remote file> telecom/devinfo.txt get: local file> devinfo-t39.txt Success, response: OK, Success (0x20) obex> put put: local file> new.vcf put: remote file> new.vcf Success, response: OK, Success (0x20) obex> di Success, response: OK, Success (0x20) In order to provide OBEX Object Push service, &man.sdpd.8; server must be running. A root folder, where all incoming objects will be stored, must be created. The default path to the root folder is /var/spool/obex. Finally, start OBEX server on valid RFCOMM channel number. The OBEX server will automatically register OBEX Object Push service with the local SDP daemon. The example below shows how to start OBEX server. &prompt.root; obexapp -s -C 10 Serial Port (SP) Profile The Serial Port (SP) profile allows Bluetooth device to perform RS232 (or similar) serial cable emulation. The scenario covered by this profile deals with legacy applications using Bluetooth as a cable replacement, through a virtual serial port abstraction. The &man.rfcomm.sppd.1; utility implements the Serial Port profile. Pseudo tty is used as a virtual serial port abstraction. The example below shows how to connect to a remote device Serial Port service. Note that you do not have to specify RFCOMM channel - &man.rfcomm.sppd.1; can obtain it from the remote device via SDP. If you would like to override this, specify RFCOMM channel in the command line. &prompt.root; rfcomm_sppd -a 00:07:E0:00:0B:CA -t /dev/ttyp6 rfcomm_sppd[94692]: Starting on /dev/ttyp6... Once connected pseudo tty can be used as serial port. &prompt.root; cu -l ttyp6 Troubleshooting A remote device cannot connect Some older Bluetooth devices do not support role switching. By default, when &os; is accepting a new connection, it tries to perform role switch and become a master. Devices, which do not support this will not be able to connect. Note the role switching is performed when a new connection is being established, so it is not possible to ask the remote device if it does support role switching. There is a HCI option to disable role switching on the local side. &prompt.root; hccontrol -n ubt0hci write_node_role_switch 0 Something is going wrong, can I see what exactly is happening? Yes, you can. Use the hcidump-1.5 third-party package that can be downloaded from here. The hcidump utility is similar to &man.tcpdump.1;. It can used to display the content of the Bluetooth packets on the terminal and to dump the Bluetooth packets to a file. Steve Peterson Written by Bridging Introduction IP subnet bridge It is sometimes useful to divide one physical network (such as an Ethernet segment) into two separate network segments without having to create IP subnets and use a router to connect the segments together. A device that connects two networks together in this fashion is called a bridge. A FreeBSD system with two network interface cards can act as a bridge. The bridge works by learning the MAC layer addresses (Ethernet addresses) of the devices on each of its network interfaces. It forwards traffic between two networks only when its source and destination are on different networks. In many respects, a bridge is like an Ethernet switch with very few ports. Situations Where Bridging Is Appropriate There are two common situations in which a bridge is used today. High Traffic on a Segment Situation one is where your physical network segment is overloaded with traffic, but you do not want for whatever reason to subnet the network and interconnect the subnets with a router. Let us consider an example of a newspaper where the Editorial and Production departments are on the same subnetwork. The Editorial users all use server A for file service, and the Production users are on server B. An Ethernet network is used to connect all users together, and high loads on the network are slowing things down. If the Editorial users could be segregated on one network segment and the Production users on another, the two network segments could be connected with a bridge. Only the network traffic destined for interfaces on the other side of the bridge would be sent to the other network, reducing congestion on each network segment. Filtering/Traffic Shaping Firewall firewall network address translation The second common situation is where firewall functionality is needed without network address translation (NAT). An example is a small company that is connected via DSL or ISDN to their ISP. They have a 13 globally-accessible IP addresses from their ISP and have 10 PCs on their network. In this situation, using a router-based firewall is difficult because of subnetting issues. router DSL ISDN A bridge-based firewall can be configured and dropped into the path just downstream of their DSL/ISDN router without any IP numbering issues. Configuring a Bridge Network Interface Card Selection A bridge requires at least two network cards to function. Unfortunately, not all network interface cards as of FreeBSD 4.0 support bridging. Read &man.bridge.4; for details on the cards that are supported. Install and test the two network cards before continuing. Kernel Configuration Changes kernel options options BRIDGE To enable kernel support for bridging, add the: options BRIDGE statement to your kernel configuration file, and rebuild your kernel. Firewall Support firewall If you are planning to use the bridge as a firewall, you will need to add the IPFIREWALL option as well. Read for general information on configuring the bridge as a firewall. If you need to allow non-IP packets (such as ARP) to flow through the bridge, there is a firewall option that must be set. This option is IPFIREWALL_DEFAULT_TO_ACCEPT. Note that this changes the default rule for the firewall to accept any packet. Make sure you know how this changes the meaning of your ruleset before you set it. Traffic Shaping Support If you want to use the bridge as a traffic shaper, you will need to add the DUMMYNET option to your kernel configuration. Read &man.dummynet.4; for further information. Enabling the Bridge Add the line: net.link.ether.bridge=1 to /etc/sysctl.conf to enable the bridge at runtime, and the line: net.link.ether.bridge_cfg=if1,if2 to enable bridging on the specified interfaces (replace if1 and if2 with the names of your two network interfaces). If you want the bridged packets to be filtered by &man.ipfw.8;, you should add: net.link.ether.bridge_ipfw=1 as well. For &os; 5.2-RELEASE and later, use instead the following lines: net.link.ether.bridge.enable=1 net.link.ether.bridge.config=if1,if2 net.link.ether.bridge.ipfw=1 Other Information If you want to be able to &man.telnet.1; into the bridge from the network, it is correct to assign one of the network cards an IP address. The consensus is that assigning both cards an address is a bad idea. If you have multiple bridges on your network, there cannot be more than one path between any two workstations. Technically, this means that there is no support for spanning tree link management. A bridge can add latency to your &man.ping.8; times, especially for traffic from one segment to another. Tom Rhodes Reorganized and enhanced by Bill Swingle Written by NFS NFS Among the many different filesystems that FreeBSD supports is the Network File System, also known as NFS. NFS allows a system to share directories and files with others over a network. By using NFS, users and programs can access files on remote systems almost as if they were local files. Some of the most notable benefits that NFS can provide are: Local workstations use less disk space because commonly used data can be stored on a single machine and still remain accessible to others over the network. There is no need for users to have separate home directories on every network machine. Home directories could be set up on the NFS server and made available throughout the network. Storage devices such as floppy disks, CDROM drives, and ZIP drives can be used by other machines on the network. This may reduce the number of removable media drives throughout the network. How <acronym>NFS</acronym> Works NFS consists of at least two main parts: a server and one or more clients. The client remotely accesses the data that is stored on the server machine. In order for this to function properly a few processes have to be configured and running: In &os; 5.X, the portmap utility has been replaced with the rpcbind utility. Thus, in &os; 5.X the user is required to replace every instance of portmap with rpcbind in the forthcoming examples. The server has to be running the following daemons: NFS server portmap mountd nfsd Daemon Description nfsd The NFS daemon which services requests from the NFS clients. mountd The NFS mount daemon which carries out the requests that &man.nfsd.8; passes on to it. portmap The portmapper daemon allows NFS clients to discover which port the NFS server is using. The client can also run a daemon, known as nfsiod. The nfsiod daemon services the requests from the NFS server. This is optional, and improves performance, but is not required for normal and correct operation. See the &man.nfsiod.8; manual page for more information. Configuring <acronym>NFS</acronym> NFS configuration NFS configuration is a relatively straightforward process. The processes that need to be running can all start at boot time with a few modifications to your /etc/rc.conf file. On the NFS server, make sure that the following options are configured in the /etc/rc.conf file: portmap_enable="YES" nfs_server_enable="YES" mountd_flags="-r" mountd runs automatically whenever the NFS server is enabled. On the client, make sure this option is present in /etc/rc.conf: nfs_client_enable="YES" The /etc/exports file specifies which filesystems NFS should export (sometimes referred to as share). Each line in /etc/exports specifies a filesystem to be exported and which machines have access to that filesystem. Along with what machines have access to that filesystem, access options may also be specified. There are many such options that can be used in this file but only a few will be mentioned here. You can easily discover other options by reading over the &man.exports.5; manual page. Here are a few example /etc/exports entries: NFS export examples The following examples give an idea of how to export filesystems, although the settings may be different depending on your environment and network configuration. For instance, to export the /cdrom directory to three example machines that have the same domain name as the server (hence the lack of a domain name for each) or have entries in your /etc/hosts file. The flag makes the exported filesystem read-only. With this flag, the remote system will not be able to write any changes to the exported filesystem. /cdrom -ro host1 host2 host3 The following line exports /home to three hosts by IP address. This is a useful setup if you have a private network without a DNS server configured. Optionally the /etc/hosts file could be configured for internal hostnames; please review &man.hosts.5; for more information. The flag allows the subdirectories to be mount points. In other words, it will not mount the subdirectories but permit the client to mount only the directories that are required or needed. /home -alldirs 10.0.0.2 10.0.0.3 10.0.0.4 The following line exports /a so that two clients from different domains may access the filesystem. The flag allows the root user on the remote system to write data on the exported filesystem as root. If the -maproot=root flag is not specified, then even if a user has root access on the remote system, they will not be able to modify files on the exported filesystem. /a -maproot=root host.example.com box.example.org In order for a client to access an exported filesystem, the client must have permission to do so. Make sure the client is listed in your /etc/exports file. In /etc/exports, each line represents the export information for one filesystem to one host. A remote host can only be specified once per filesystem, and may only have one default entry. For example, assume that /usr is a single filesystem. The following /etc/exports would be invalid: /usr/src client /usr/ports client One filesystem, /usr, has two lines specifying exports to the same host, client. The correct format for this situation is: /usr/src /usr/ports client The properties of one filesystem exported to a given host must all occur on one line. Lines without a client specified are treated as a single host. This limits how you can export filesystems, but for most people this is not an issue. The following is an example of a valid export list, where /usr and /exports are local filesystems: # Export src and ports to client01 and client02, but only # client01 has root privileges on it /usr/src /usr/ports -maproot=root client01 /usr/src /usr/ports client02 # The client machines have root and can mount anywhere # on /exports. Anyone in the world can mount /exports/obj read-only /exports -alldirs -maproot=root client01 client02 /exports/obj -ro You must restart mountd whenever you modify /etc/exports so the changes can take effect. This can be accomplished by sending the HUP signal to the mountd process: &prompt.root; kill -HUP `cat /var/run/mountd.pid` Alternatively, a reboot will make FreeBSD set everything up properly. A reboot is not necessary though. Executing the following commands as root should start everything up. On the NFS server: &prompt.root; portmap &prompt.root; nfsd -u -t -n 4 &prompt.root; mountd -r On the NFS client: &prompt.root; nfsiod -n 4 Now everything should be ready to actually mount a remote file system. In these examples the server's name will be server and the client's name will be client. If you only want to temporarily mount a remote filesystem or would rather test the configuration, just execute a command like this as root on the client: NFS mounting &prompt.root; mount server:/home /mnt This will mount the /home directory on the server at /mnt on the client. If everything is set up correctly you should be able to enter /mnt on the client and see all the files that are on the server. If you want to automatically mount a remote filesystem each time the computer boots, add the filesystem to the /etc/fstab file. Here is an example: server:/home /mnt nfs rw 0 0 The &man.fstab.5; manual page lists all the available options. Practical Uses NFS has many practical uses. Some of the more common ones are listed below: NFS uses Set several machines to share a CDROM or other media among them. This is cheaper and often a more convenient method to install software on multiple machines. On large networks, it might be more convenient to configure a central NFS server in which to store all the user home directories. These home directories can then be exported to the network so that users would always have the same home directory, regardless of which workstation they log in to. Several machines could have a common /usr/ports/distfiles directory. That way, when you need to install a port on several machines, you can quickly access the source without downloading it on each machine. Wylie Stilwell Contributed by Chern Lee Rewritten by Automatic Mounts with <application>amd</application> amd automatic mounter daemon &man.amd.8; (the automatic mounter daemon) automatically mounts a remote filesystem whenever a file or directory within that filesystem is accessed. Filesystems that are inactive for a period of time will also be automatically unmounted by amd. Using amd provides a simple alternative to permanent mounts, as permanent mounts are usually listed in /etc/fstab. amd operates by attaching itself as an NFS server to the /host and /net directories. When a file is accessed within one of these directories, amd looks up the corresponding remote mount and automatically mounts it. /net is used to mount an exported filesystem from an IP address, while /host is used to mount an export from a remote hostname. An access to a file within /host/foobar/usr would tell amd to attempt to mount the /usr export on the host foobar. Mounting an Export with <application>amd</application> You can view the available mounts of a remote host with the showmount command. For example, to view the mounts of a host named foobar, you can use: &prompt.user; showmount -e foobar Exports list on foobar: /usr 10.10.10.0 /a 10.10.10.0 &prompt.user; cd /host/foobar/usr As seen in the example, the showmount shows /usr as an export. When changing directories to /host/foobar/usr, amd attempts to resolve the hostname foobar and automatically mount the desired export. amd can be started by the startup scripts by placing the following lines in /etc/rc.conf: amd_enable="YES" Additionally, custom flags can be passed to amd from the amd_flags option. By default, amd_flags is set to: amd_flags="-a /.amd_mnt -l syslog /host /etc/amd.map /net /etc/amd.map" The /etc/amd.map file defines the default options that exports are mounted with. The /etc/amd.conf file defines some of the more advanced features of amd. Consult the &man.amd.8; and &man.amd.conf.5; manual pages for more information. John Lind Contributed by Problems Integrating with Other Systems Certain Ethernet adapters for ISA PC systems have limitations which can lead to serious network problems, particularly with NFS. This difficulty is not specific to FreeBSD, but FreeBSD systems are affected by it. The problem nearly always occurs when (FreeBSD) PC systems are networked with high-performance workstations, such as those made by Silicon Graphics, Inc., and Sun Microsystems, Inc. The NFS mount will work fine, and some operations may succeed, but suddenly the server will seem to become unresponsive to the client, even though requests to and from other systems continue to be processed. This happens to the client system, whether the client is the FreeBSD system or the workstation. On many systems, there is no way to shut down the client gracefully once this problem has manifested itself. The only solution is often to reset the client, because the NFS situation cannot be resolved. Though the correct solution is to get a higher performance and capacity Ethernet adapter for the FreeBSD system, there is a simple workaround that will allow satisfactory operation. If the FreeBSD system is the server, include the option on the mount from the client. If the FreeBSD system is the client, then mount the NFS filesystem with the option . These options may be specified using the fourth field of the fstab entry on the client for automatic mounts, or by using the parameter of the mount command for manual mounts. It should be noted that there is a different problem, sometimes mistaken for this one, when the NFS servers and clients are on different networks. If that is the case, make certain that your routers are routing the necessary UDP information, or you will not get anywhere, no matter what else you are doing. In the following examples, fastws is the host (interface) name of a high-performance workstation, and freebox is the host (interface) name of a FreeBSD system with a lower-performance Ethernet adapter. Also, /sharedfs will be the exported NFS filesystem (see &man.exports.5;), and /project will be the mount point on the client for the exported filesystem. In all cases, note that additional options, such as or and may be desirable in your application. Examples for the FreeBSD system (freebox) as the client in /etc/fstab on freebox: fastws:/sharedfs /project nfs rw,-r=1024 0 0 As a manual mount command on freebox: &prompt.root; mount -t nfs -o -r=1024 fastws:/sharedfs /project Examples for the FreeBSD system as the server in /etc/fstab on fastws: freebox:/sharedfs /project nfs rw,-w=1024 0 0 As a manual mount command on fastws: &prompt.root; mount -t nfs -o -w=1024 freebox:/sharedfs /project Nearly any 16-bit Ethernet adapter will allow operation without the above restrictions on the read or write size. For anyone who cares, here is what happens when the failure occurs, which also explains why it is unrecoverable. NFS typically works with a block size of 8 k (though it may do fragments of smaller sizes). Since the maximum Ethernet packet is around 1500 bytes, the NFS block gets split into multiple Ethernet packets, even though it is still a single unit to the upper-level code, and must be received, assembled, and acknowledged as a unit. The high-performance workstations can pump out the packets which comprise the NFS unit one right after the other, just as close together as the standard allows. On the smaller, lower capacity cards, the later packets overrun the earlier packets of the same unit before they can be transferred to the host and the unit as a whole cannot be reconstructed or acknowledged. As a result, the workstation will time out and try again, but it will try again with the entire 8 K unit, and the process will be repeated, ad infinitum. By keeping the unit size below the Ethernet packet size limitation, we ensure that any complete Ethernet packet received can be acknowledged individually, avoiding the deadlock situation. Overruns may still occur when a high-performance workstations is slamming data out to a PC system, but with the better cards, such overruns are not guaranteed on NFS units. When an overrun occurs, the units affected will be retransmitted, and there will be a fair chance that they will be received, assembled, and acknowledged. Jean-François Dockès Updated by Alex Dupre Reorganized and enhanced by Diskless Operation diskless workstation diskless operation A FreeBSD machine can boot over the network and operate without a local disk, using filesystems mounted from an NFS server. No system modification is necessary, beyond standard configuration files. Such a system is relatively easy to set up because all the necessary elements are readily available: There are at least two possible methods to load the kernel over the network: PXE: The &intel; Preboot Execution Environment system is a form of smart boot ROM built into some networking cards or motherboards. See &man.pxeboot.8; for more details. The etherboot port (net/etherboot) produces ROM-able code to boot kernels over the network. The code can be either burnt into a boot PROM on a network card, or loaded from a local floppy (or hard) disk drive, or from a running &ms-dos; system. Many network cards are supported. A sample script (/usr/share/examples/diskless/clone_root) eases the creation and maintenance of the workstation's root filesystem on the server. The script will probably require a little customization but it will get you started very quickly. Standard system startup files exist in /etc to detect and support a diskless system startup. Swapping, if needed, can be done either to an NFS file or to a local disk. There are many ways to set up diskless workstations. Many elements are involved, and most can be customized to suit local taste. The following will describe variations on the setup of a complete system, emphasizing simplicity and compatibility with the standard FreeBSD startup scripts. The system described has the following characteristics: The diskless workstations use a shared read-only root filesystem, and a shared read-only /usr. The root filesystem is a copy of a standard FreeBSD root (typically the server's), with some configuration files overridden by ones specific to diskless operation or, possibly, to the workstation they belong to. The parts of the root which have to be writable are overlaid with &man.mfs.8; (&os; 4.X) or &man.md.4; (&os; 5.X) filesystems. Any changes will be lost when the system reboots. The kernel is transferred and loaded either with etherboot or PXE as some situations may mandate the use of either method. As described, this system is insecure. It should live in a protected area of a network, and be untrusted by other hosts. All the information in this section has been tested using &os; releases 4.9-RELEASE and 5.2.1-RELEASE. The text is primarily structured for 4.X usage. Notes have been inserted where appropriate to indicate 5.X changes. Background Information Setting up diskless workstations is both relatively straightforward and prone to errors. These are sometimes difficult to diagnose for a number of reasons. For example: Compile time options may determine different behaviours at runtime. Error messages are often cryptic or totally absent. In this context, having some knowledge of the background mechanisms involved is very useful to solve the problems that may arise. Several operations need to be performed for a successful bootstrap: The machine needs to obtain initial parameters such as its IP address, executable filename, server name, root path. This is done using the DHCP or BOOTP protocols. DHCP is a compatible extension of BOOTP, and uses the same port numbers and basic packet format. It is possible to configure a system to use only BOOTP. The &man.bootpd.8; server program is included in the base &os; system. However, DHCP has a number of advantages over BOOTP (nicer configuration files, possibility of using PXE, plus many others not directly related to diskless operation), and we will describe mainly a DHCP configuration, with equivalent exemples using &man.bootpd.8; when possible. The sample configuration will use the ISC DHCP software package (release 3.0.1.r12 was installed on the test server). The machine needs to transfer one or several programs to local memory. Either TFTP or NFS are used. The choice between TFTP and NFS is a compile time option in several places. A common source of error is to specify filenames for the wrong protocol: TFTP typically transfers all files from a single directory on the server, and would expect filenames relative to this directory. NFS needs absolute file paths. The possible intermediate bootstrap programs and the kernel need to be initialized and executed. There are several important variations in this area: PXE will load &man.pxeboot.8;, which is a modified version of the &os; third stage loader. The &man.loader.8; will obtain most parameters necessary to system startup, and leave them in the kernel environment before transferring control. It is possible to use a GENERIC kernel in this case. etherboot, will directly load the kernel, with less preparation. You will need to build a kernel with specific options. PXE and etherboot work equally well with 4.X systems. Because 5.X kernels normally let the &man.loader.8; do more work for them, PXE is preferred for 5.X systems. If your BIOS and network cards support PXE, you should probably use it. However, it is still possible to start a 5.X system with etherboot. Finally, the machine needs to access its filesystems. NFS is used in all cases. See also &man.diskless.8; manual page. Setup Instructions Configuration Using <application>ISC DHCP</application> DHCP diskless operation The ISC DHCP server can answer both BOOTP and DHCP requests. As of release 4.9, ISC DHCP 3.0 is not part of the base system. You will first need to install the net/isc-dhcp3-server port or the corresponding package. Please refer to for general information about ports and packages. Once ISC DHCP is installed, it needs a configuration file to run, (normally named /usr/local/etc/dhcpd.conf). Here follows a commented example, where host margaux uses etherboot and host corbieres uses PXE: default-lease-time 600; max-lease-time 7200; authoritative; option domain-name "example.com"; option domain-name-servers 192.168.4.1; option routers 192.168.4.1; subnet 192.168.4.0 netmask 255.255.255.0 { use-host-decl-names on; option subnet-mask 255.255.255.0; option broadcast-address 192.168.4.255; host margaux { hardware ethernet 01:23:45:67:89:ab; fixed-address margaux.example.com; next-server 192.168.4.4; filename "/data/misc/kernel.diskless"; option root-path "192.168.4.4:/data/misc/diskless"; } host corbieres { hardware ethernet 00:02:b3:27:62:df; fixed-address corbieres.example.com; next-server 192.168.4.4; filename "pxeboot"; option root-path "192.168.4.4:/data/misc/diskless"; } } This option tells dhcpd to send the value in the host declarations as the hostname for the diskless host. An alternate way would be to add an option host-name margaux inside the host declarations. The next-server directive designates the TFTP or NFS server to use for loading loader or kernel file (the default is to use the same host as the DHCP server). The filename directive defines the file that etherboot or PXE will load for the next execution step. It must be specified according to the transfer method used. etherboot can be compiled to use NFS or TFTP. The &os; port configures NFS by default. PXE uses TFTP, which is why a relative filename is used here (this may depend on the TFTP server configuration, but would be fairly typical). Also, PXE loads pxeboot, not the kernel. There are other interesting possibilities, like loading pxeboot from a &os; CD-ROM /boot directory (as &man.pxeboot.8; can load a GENERIC kernel, this makes it possible to use PXE to boot from a remote CD-ROM). The root-path option defines the path to the root filesystem, in usual NFS notation. When using PXE, it is possible to leave off the host's IP as long as you do not enable the kernel option BOOTP. The NFS server will then be the same as the TFTP one. Configuration Using BOOTP BOOTP diskless operation Here follows an equivalent bootpd configuration (reduced to one client). This would be found in /etc/bootptab. Please note that etherboot must be compiled with the non-default option NO_DHCP_SUPPORT in order to use BOOTP, and that PXE needs DHCP. The only obvious advantage of bootpd is that it exists in the base system. .def100:\ :hn:ht=1:sa=192.168.4.4:vm=rfc1048:\ :sm=255.255.255.0:\ :ds=192.168.4.1:\ :gw=192.168.4.1:\ :hd="/tftpboot":\ :bf="/kernel.diskless":\ :rp="192.168.4.4:/data/misc/diskless": margaux:ha=0123456789ab:tc=.def100 Preparing a Boot Program with <application>Etherboot</application> Etherboot Etherboot's Web site contains extensive documentation mainly intended for Linux systems, but nonetheless containing useful information. The following will just outline how you would use etherboot on a FreeBSD system. You must first install the net/etherboot package or port. The etherboot port can normally be found in /usr/ports/net/etherboot. If the ports tree is installed on your system, just typing make in this directory should take care of everything. Else refer to for information about ports and packages. You can change the etherboot configuration (i.e. to use TFTP instead of NFS) by editing the Config file in the etherboot source directory. For our setup, we shall use a boot floppy. For other methods (PROM, or &ms-dos; program), please refer to the etherboot documentation. To make a boot floppy, insert a floppy in the drive on the machine where you installed etherboot, then change your current directory to the src directory in the etherboot tree and type: &prompt.root; gmake bin32/devicetype.fd0 devicetype depends on the type of the Ethernet card in the diskless workstation. Refer to the NIC file in the same directory to determine the right devicetype. Booting with <acronym>PXE</acronym> By default, the &man.pxeboot.8; loader loads the kernel via NFS. It can be compiled to use TFTP instead by specifying the LOADER_TFTP_SUPPORT option in /etc/make.conf. See the comments in /etc/defaults/make.conf (or /usr/share/examples/etc/make.conf for 5.X systems) for instructions. There are two other undocumented make.conf options which may be useful for setting up a serial console diskless machine: BOOT_PXELDR_PROBE_KEYBOARD, and BOOT_PXELDR_ALWAYS_SERIAL (the latter only exists on &os; 5.X). To use PXE when the machine starts, you will usually need to select the Boot from network option in your BIOS setup, or type a function key during the PC initialization. Configuring the <acronym>TFTP</acronym> and <acronym>NFS</acronym> Servers TFTP diskless operation NFS diskless operation If you are using PXE or etherboot configured to use TFTP, you need to enable tftpd on the file server: Create a directory from which tftpd will serve the files, e.g. /tftpboot. Add this line to your /etc/inetd.conf: tftp dgram udp wait root /usr/libexec/tftpd tftpd -l -s /tftpboot It appears that at least some PXE versions want the TCP version of TFTP. In this case, add a second line, replacing dgram udp with stream tcp. Tell inetd to reread its configuration file: &prompt.root; kill -HUP `cat /var/run/inetd.pid` You can place the tftpboot directory anywhere on the server. Make sure that the location is set in both inetd.conf and dhcpd.conf. In all cases, you also need to enable NFS and export the appropriate filesystem on the NFS server. Add this to /etc/rc.conf: nfs_server_enable="YES" Export the filesystem where the diskless root directory is located by adding the following to /etc/exports (adjust the volume mount point and replace margaux corbieres with the names of the diskless workstations): /data/misc -alldirs -ro margaux corbieres Tell mountd to reread its configuration file. If you actually needed to enable NFS in /etc/rc.conf at the first step, you probably want to reboot instead. &prompt.root; kill -HUP `cat /var/run/mountd.pid` Building a Diskless Kernel diskless operation kernel configuration If using etherboot, you need to create a kernel configuration file for the diskless client with the following options (in addition to the usual ones): options BOOTP # Use BOOTP to obtain IP address/hostname options BOOTP_NFSROOT # NFS mount root filesystem using BOOTP info You may also want to use BOOTP_NFSV3, BOOT_COMPAT and BOOTP_WIRED_TO (refer to LINT in 4.X or NOTES on 5.X). These option names are historical and slightly misleading as they actually enable indifferent use of DHCP and BOOTP inside the kernel (it is also possible to force strict BOOTP or DHCP use). Build the kernel (see ), and copy it to the place specified in dhcpd.conf. When using PXE, building a kernel with the above options is not strictly necessary (though suggested). Enabling them will cause more DHCP requests to be issued during kernel startup, with a small risk of inconsistency between the new values and those retrieved by &man.pxeboot.8; in some special cases. The advantage of using them is that the host name will be set as a side effect. Otherwise you will need to set the host name by another method, for example in a client-specific rc.conf file. In order to be loadable with etherboot, a 5.X kernel needs to have the device hints compiled in. You would typically set the following option in the configuration file (see the NOTES configuration comments file): hints "GENERIC.hints" Preparing the Root Filesystem root file system diskless operation You need to create a root filesystem for the diskless workstations, in the location listed as root-path in dhcpd.conf. The following sections describe two ways to do it. Using the <filename>clone_root</filename> Script This is the quickest way to create a root filesystem, but currently it is only supported on &os; 4.X. This shell script is located at /usr/share/examples/diskless/clone_root and needs customization, at least to adjust the place where the filesystem will be created (the DEST variable). Refer to the comments at the top of the script for instructions. They explain how the base filesystem is built, and how files may be selectively overridden by versions specific to diskless operation, to a subnetwork, or to an individual workstation. They also give examples for the diskless /etc/fstab and /etc/rc.conf files. The README files in /usr/share/examples/diskless contain a lot of interesting background information, but, together with the other examples in the diskless directory, they actually document a configuration method which is distinct from the one used by clone_root and the system startup scripts in /etc, which is a little confusing. Use them for reference only, except if you prefer the method that they describe, in which case you will need customized rc scripts. Using the Standard <command>make world</command> Procedure This method can be applied to either &os; 4.X or 5.X and will install a complete virgin system (not only the root filesystem) into DESTDIR. All you have to do is simply execute the following script: #!/bin/sh export DESTDIR=/data/misc/diskless mkdir -p ${DESTDIR} cd /usr/src; make world && make kernel cd /usr/src/etc; make distribution Once done, you may need to customize your /etc/rc.conf and /etc/fstab placed into DESTDIR according to your needs. Configuring Swap If needed, a swap file located on the server can be accessed via NFS. One of the methods commonly used to do this has been discontinued in release 5.X. <acronym>NFS</acronym> Swap with &os; 4.X The swap file location and size can be specified with BOOTP/DHCP &os;-specific options 128 and 129. Examples of configuration files for ISC DHCP 3.0 or bootpd follow: Add the following lines to dhcpd.conf: # Global section option swap-path code 128 = string; option swap-size code 129 = integer 32; host margaux { ... # Standard lines, see above option swap-path "192.168.4.4:/netswapvolume/netswap"; option swap-size 64000; } swap-path is the path to a directory where swap files will be located. Each file will be named swap.client-ip. Older versions of dhcpd used a syntax of option option-128 "..., which is no longer supported. /etc/bootptab would use the following syntax instead: T128="192.168.4.4:/netswapvolume/netswap":T129=0000fa00 In /etc/bootptab, the swap size must be expressed in hexadecimal format. On the NFS swap file server, create the swap file(s) &prompt.root; mkdir /netswapvolume/netswap &prompt.root; cd /netswapvolume/netswap &prompt.root; dd if=/dev/zero bs=1024 count=64000 of=swap.192.168.4.6 &prompt.root; chmod 0600 swap.192.168.4.6 192.168.4.6 is the IP address for the diskless client. On the NFS swap file server, add the following line to /etc/exports: /netswapvolume -maproot=0:10 -alldirs margaux corbieres Then tell mountd to reread the exports file, as above. <acronym>NFS</acronym> Swap with &os 5.X The kernel does not support enabling NFS swap at boot time. Swap must be enabled by the startup scripts, by mounting a writeable file system and creating and enabling a swap file. To create a swap file of appropriate size, you can do like this: &prompt.root; dd if=/dev/zero of=/path/to/swapfile bs=1k count=1 oseek=100000 To enable it you have to add the following line to your rc.conf: swapfile=/path/to/swapfile Miscellaneous Issues Running with a Read-only <filename>/usr</filename> diskless operation /usr read-only If the diskless workstation is configured to run X, you will have to adjust the xdm configuration file, which puts the error log on /usr by default. Using a Non-FreeBSD Server When the server for the root filesystem is not running FreeBSD, you will have to create the root filesystem on a FreeBSD machine, then copy it to its destination, using tar or cpio. In this situation, there are sometimes problems with the special files in /dev, due to differing major/minor integer sizes. A solution to this problem is to export a directory from the non-FreeBSD server, mount this directory onto a FreeBSD machine, and run MAKEDEV on the FreeBSD machine to create the correct device entries (FreeBSD 5.0 and later use &man.devfs.5; to allocate device nodes transparently for the user, running MAKEDEV on these versions is pointless). ISDN ISDN A good resource for information on ISDN technology and hardware is Dan Kegel's ISDN Page. A quick simple road map to ISDN follows: If you live in Europe you might want to investigate the ISDN card section. If you are planning to use ISDN primarily to connect to the Internet with an Internet Provider on a dial-up non-dedicated basis, you might look into Terminal Adapters. This will give you the most flexibility, with the fewest problems, if you change providers. If you are connecting two LANs together, or connecting to the Internet with a dedicated ISDN connection, you might consider the stand alone router/bridge option. Cost is a significant factor in determining what solution you will choose. The following options are listed from least expensive to most expensive. Hellmuth Michaelis Contributed by ISDN Cards ISDN cards FreeBSD's ISDN implementation supports only the DSS1/Q.931 (or Euro-ISDN) standard using passive cards. Starting with FreeBSD 4.4, some active cards are supported where the firmware also supports other signaling protocols; this also includes the first supported Primary Rate (PRI) ISDN card. The isdn4bsd software allows you to connect to other ISDN routers using either IP over raw HDLC or by using synchronous PPP: either by using kernel PPP with isppp, a modified &man.sppp.4; driver, or by using userland &man.ppp.8;. By using userland &man.ppp.8;, channel bonding of two or more ISDN B-channels is possible. A telephone answering machine application is also available as well as many utilities such as a software 300 Baud modem. Some growing number of PC ISDN cards are supported under FreeBSD and the reports show that it is successfully used all over Europe and in many other parts of the world. The passive ISDN cards supported are mostly the ones with the Infineon (formerly Siemens) ISAC/HSCX/IPAC ISDN chipsets, but also ISDN cards with chips from Cologne Chip (ISA bus only), PCI cards with Winbond W6692 chips, some cards with the Tiger300/320/ISAC chipset combinations and some vendor specific chipset based cards such as the AVM Fritz!Card PCI V.1.0 and the AVM Fritz!Card PnP. Currently the active supported ISDN cards are the AVM B1 (ISA and PCI) BRI cards and the AVM T1 PCI PRI cards. For documentation on isdn4bsd, have a look at /usr/share/examples/isdn/ directory on your FreeBSD system or at the homepage of isdn4bsd which also has pointers to hints, erratas and much more documentation such as the isdn4bsd handbook. In case you are interested in adding support for a different ISDN protocol, a currently unsupported ISDN PC card or otherwise enhancing isdn4bsd, please get in touch with &a.hm;. For questions regarding the installation, configuration and troubleshooting isdn4bsd, a &a.isdn.name; mailing list is available. ISDN Terminal Adapters Terminal adapters (TA), are to ISDN what modems are to regular phone lines. modem Most TA's use the standard Hayes modem AT command set, and can be used as a drop in replacement for a modem. A TA will operate basically the same as a modem except connection and throughput speeds will be much faster than your old modem. You will need to configure PPP exactly the same as for a modem setup. Make sure you set your serial speed as high as possible. PPP The main advantage of using a TA to connect to an Internet Provider is that you can do Dynamic PPP. As IP address space becomes more and more scarce, most providers are not willing to provide you with a static IP anymore. Most stand-alone routers are not able to accommodate dynamic IP allocation. TA's completely rely on the PPP daemon that you are running for their features and stability of connection. This allows you to upgrade easily from using a modem to ISDN on a FreeBSD machine, if you already have PPP set up. However, at the same time any problems you experienced with the PPP program and are going to persist. If you want maximum stability, use the kernel PPP option, not the userland PPP. The following TA's are known to work with FreeBSD: Motorola BitSurfer and Bitsurfer Pro Adtran Most other TA's will probably work as well, TA vendors try to make sure their product can accept most of the standard modem AT command set. The real problem with external TA's is that, like modems, you need a good serial card in your computer. You should read the FreeBSD Serial Hardware tutorial for a detailed understanding of serial devices, and the differences between asynchronous and synchronous serial ports. A TA running off a standard PC serial port (asynchronous) limits you to 115.2 Kbs, even though you have a 128 Kbs connection. To fully utilize the 128 Kbs that ISDN is capable of, you must move the TA to a synchronous serial card. Do not be fooled into buying an internal TA and thinking you have avoided the synchronous/asynchronous issue. Internal TA's simply have a standard PC serial port chip built into them. All this will do is save you having to buy another serial cable and find another empty electrical socket. A synchronous card with a TA is at least as fast as a stand-alone router, and with a simple 386 FreeBSD box driving it, probably more flexible. The choice of synchronous card/TA v.s. stand-alone router is largely a religious issue. There has been some discussion of this in the mailing lists. We suggest you search the archives for the complete discussion. Stand-alone ISDN Bridges/Routers ISDN stand-alone bridges/routers ISDN bridges or routers are not at all specific to FreeBSD or any other operating system. For a more complete description of routing and bridging technology, please refer to a networking reference book. In the context of this section, the terms router and bridge will be used interchangeably. As the cost of low end ISDN routers/bridges comes down, it will likely become a more and more popular choice. An ISDN router is a small box that plugs directly into your local Ethernet network, and manages its own connection to the other bridge/router. It has built in software to communicate via PPP and other popular protocols. A router will allow you much faster throughput than a standard TA, since it will be using a full synchronous ISDN connection. The main problem with ISDN routers and bridges is that interoperability between manufacturers can still be a problem. If you are planning to connect to an Internet provider, you should discuss your needs with them. If you are planning to connect two LAN segments together, such as your home LAN to the office LAN, this is the simplest lowest maintenance solution. Since you are buying the equipment for both sides of the connection you can be assured that the link will work. For example to connect a home computer or branch office network to a head office network the following setup could be used: Branch Office or Home Network 10 base 2 Network uses a bus based topology with 10 base 2 Ethernet (thinnet). Connect router to network cable with AUI/10BT transceiver, if necessary. ---Sun workstation | ---FreeBSD box | ---Windows 95 | Stand-alone router | ISDN BRI line 10 Base 2 Ethernet If your home/branch office is only one computer you can use a twisted pair crossover cable to connect to the stand-alone router directly. Head Office or Other LAN 10 base T Network uses a star topology with 10 base T Ethernet (Twisted Pair). -------Novell Server | H | | ---Sun | | | U ---FreeBSD | | | ---Windows 95 | B | |___---Stand-alone router | ISDN BRI line ISDN Network Diagram One large advantage of most routers/bridges is that they allow you to have 2 separate independent PPP connections to 2 separate sites at the same time. This is not supported on most TA's, except for specific (usually expensive) models that have two serial ports. Do not confuse this with channel bonding, MPP, etc. This can be a very useful feature if, for example, you have an dedicated ISDN connection at your office and would like to tap into it, but do not want to get another ISDN line at work. A router at the office location can manage a dedicated B channel connection (64 Kbps) to the Internet and use the other B channel for a separate data connection. The second B channel can be used for dial-in, dial-out or dynamically bonding (MPP, etc.) with the first B channel for more bandwidth. IPX/SPX An Ethernet bridge will also allow you to transmit more than just IP traffic. You can also send IPX/SPX or whatever other protocols you use. Bill Swingle Written by Eric Ogren Enhanced by Udo Erdelhoff NIS/YP What Is It? NIS Solaris HP-UX AIX Linux NetBSD OpenBSD NIS, which stands for Network Information Services, was developed by Sun Microsystems to centralize administration of &unix; (originally &sunos;) systems. It has now essentially become an industry standard; all major &unix; like systems (&solaris;, HP-UX, &aix;, Linux, NetBSD, OpenBSD, FreeBSD, etc) support NIS. yellow pagesNIS NIS was formerly known as Yellow Pages, but because of trademark issues, Sun changed the name. The old term (and yp) is still often seen and used. NIS domains It is a RPC-based client/server system that allows a group of machines within an NIS domain to share a common set of configuration files. This permits a system administrator to set up NIS client systems with only minimal configuration data and add, remove or modify configuration data from a single location. Windows NT It is similar to the &windowsnt; domain system; although the internal implementation of the two are not at all similar, the basic functionality can be compared. Terms/Processes You Should Know There are several terms and several important user processes that you will come across when attempting to implement NIS on FreeBSD, whether you are trying to create an NIS server or act as an NIS client: portmap Term Description NIS domainname An NIS master server and all of its clients (including its slave servers) have a NIS domainname. Similar to an &windowsnt; domain name, the NIS domainname does not have anything to do with DNS. portmap Must be running in order to enable RPC (Remote Procedure Call, a network protocol used by NIS). If portmap is not running, it will be impossible to run an NIS server, or to act as an NIS client. ypbind Binds an NIS client to its NIS server. It will take the NIS domainname from the system, and using RPC, connect to the server. ypbind is the core of client-server communication in an NIS environment; if ypbind dies on a client machine, it will not be able to access the NIS server. ypserv Should only be running on NIS servers; this is the NIS server process itself. If &man.ypserv.8; dies, then the server will no longer be able to respond to NIS requests (hopefully, there is a slave server to take over for it). There are some implementations of NIS (but not the FreeBSD one), that do not try to reconnect to another server if the server it used before dies. Often, the only thing that helps in this case is to restart the server process (or even the whole server) or the ypbind process on the client. rpc.yppasswdd Another process that should only be running on NIS master servers; this is a daemon that will allow NIS clients to change their NIS passwords. If this daemon is not running, users will have to login to the NIS master server and change their passwords there. How Does It Work? There are three types of hosts in an NIS environment: master servers, slave servers, and clients. Servers act as a central repository for host configuration information. Master servers hold the authoritative copy of this information, while slave servers mirror this information for redundancy. Clients rely on the servers to provide this information to them. Information in many files can be shared in this manner. The master.passwd, group, and hosts files are commonly shared via NIS. Whenever a process on a client needs information that would normally be found in these files locally, it makes a query to the NIS server that it is bound to instead. Machine Types NIS master server A NIS master server. This server, analogous to a &windowsnt; primary domain controller, maintains the files used by all of the NIS clients. The passwd, group, and other various files used by the NIS clients live on the master server. It is possible for one machine to be an NIS master server for more than one NIS domain. However, this will not be covered in this introduction, which assumes a relatively small-scale NIS environment. NIS slave server NIS slave servers. Similar to the &windowsnt; backup domain controllers, NIS slave servers maintain copies of the NIS master's data files. NIS slave servers provide the redundancy, which is needed in important environments. They also help to balance the load of the master server: NIS Clients always attach to the NIS server whose response they get first, and this includes slave-server-replies. NIS client NIS clients. NIS clients, like most &windowsnt; workstations, authenticate against the NIS server (or the &windowsnt; domain controller in the &windowsnt; Workstation case) to log on. Using NIS/YP This section will deal with setting up a sample NIS environment. This section assumes that you are running FreeBSD 3.3 or later. The instructions given here will probably work for any version of FreeBSD greater than 3.0, but there are no guarantees that this is true. Planning Let us assume that you are the administrator of a small university lab. This lab, which consists of 15 FreeBSD machines, currently has no centralized point of administration; each machine has its own /etc/passwd and /etc/master.passwd. These files are kept in sync with each other only through manual intervention; currently, when you add a user to the lab, you must run adduser on all 15 machines. Clearly, this has to change, so you have decided to convert the lab to use NIS, using two of the machines as servers. Therefore, the configuration of the lab now looks something like: Machine name IP address Machine role ellington 10.0.0.2 NIS master coltrane 10.0.0.3 NIS slave basie 10.0.0.4 Faculty workstation bird 10.0.0.5 Client machine cli[1-11] 10.0.0.[6-17] Other client machines If you are setting up a NIS scheme for the first time, it is a good idea to think through how you want to go about it. No matter what the size of your network, there are a few decisions that need to be made. Choosing a NIS Domain Name NIS domainname This might not be the domainname that you are used to. It is more accurately called the NIS domainname. When a client broadcasts its requests for info, it includes the name of the NIS domain that it is part of. This is how multiple servers on one network can tell which server should answer which request. Think of the NIS domainname as the name for a group of hosts that are related in some way. Some organizations choose to use their Internet domainname for their NIS domainname. This is not recommended as it can cause confusion when trying to debug network problems. The NIS domainname should be unique within your network and it is helpful if it describes the group of machines it represents. For example, the Art department at Acme Inc. might be in the acme-art NIS domain. For this example, assume you have chosen the name test-domain. SunOS However, some operating systems (notably &sunos;) use their NIS domain name as their Internet domain name. If one or more machines on your network have this restriction, you must use the Internet domain name as your NIS domain name. Physical Server Requirements There are several things to keep in mind when choosing a machine to use as a NIS server. One of the unfortunate things about NIS is the level of dependency the clients have on the server. If a client cannot contact the server for its NIS domain, very often the machine becomes unusable. The lack of user and group information causes most systems to temporarily freeze up. With this in mind you should make sure to choose a machine that will not be prone to being rebooted regularly, or one that might be used for development. The NIS server should ideally be a stand alone machine whose sole purpose in life is to be an NIS server. If you have a network that is not very heavily used, it is acceptable to put the NIS server on a machine running other services, just keep in mind that if the NIS server becomes unavailable, it will affect all of your NIS clients adversely. NIS Servers The canonical copies of all NIS information are stored on a single machine called the NIS master server. The databases used to store the information are called NIS maps. In FreeBSD, these maps are stored in /var/yp/[domainname] where [domainname] is the name of the NIS domain being served. A single NIS server can support several domains at once, therefore it is possible to have several such directories, one for each supported domain. Each domain will have its own independent set of maps. NIS master and slave servers handle all NIS requests with the ypserv daemon. ypserv is responsible for receiving incoming requests from NIS clients, translating the requested domain and map name to a path to the corresponding database file and transmitting data from the database back to the client. Setting Up a NIS Master Server NIS server configuration Setting up a master NIS server can be relatively straight forward, depending on your needs. FreeBSD comes with support for NIS out-of-the-box. All you need is to add the following lines to /etc/rc.conf, and FreeBSD will do the rest for you. nisdomainname="test-domain" This line will set the NIS domainname to test-domain upon network setup (e.g. after reboot). nis_server_enable="YES" This will tell FreeBSD to start up the NIS server processes when the networking is next brought up. nis_yppasswdd_enable="YES" This will enable the rpc.yppasswdd daemon which, as mentioned above, will allow users to change their NIS password from a client machine. Depending on your NIS setup, you may need to add further entries. See the section about NIS servers that are also NIS clients, below, for details. Now, all you have to do is to run the command /etc/netstart as superuser. It will set up everything for you, using the values you defined in /etc/rc.conf. Initializing the NIS Maps NIS maps The NIS maps are database files, that are kept in the /var/yp directory. They are generated from configuration files in the /etc directory of the NIS master, with one exception: the /etc/master.passwd file. This is for a good reason; you do not want to propagate passwords to your root and other administrative accounts to all the servers in the NIS domain. Therefore, before we initialize the NIS maps, you should: &prompt.root; cp /etc/master.passwd /var/yp/master.passwd &prompt.root; cd /var/yp &prompt.root; vi master.passwd You should remove all entries regarding system accounts (bin, tty, kmem, games, etc), as well as any accounts that you do not want to be propagated to the NIS clients (for example root and any other UID 0 (superuser) accounts). Make sure the /var/yp/master.passwd is neither group nor world readable (mode 600)! Use the chmod command, if appropriate. Tru64 UNIX When you have finished, it is time to initialize the NIS maps! FreeBSD includes a script named ypinit to do this for you (see its manual page for more information). Note that this script is available on most &unix; Operating Systems, but not on all. On Digital UNIX/Compaq Tru64 UNIX it is called ypsetup. Because we are generating maps for an NIS master, we are going to pass the option to ypinit. To generate the NIS maps, assuming you already performed the steps above, run: ellington&prompt.root; ypinit -m test-domain Server Type: MASTER Domain: test-domain Creating an YP server will require that you answer a few questions. Questions will all be asked at the beginning of the procedure. Do you want this procedure to quit on non-fatal errors? [y/n: n] n Ok, please remember to go back and redo manually whatever fails. If you don't, something might not work. At this point, we have to construct a list of this domains YP servers. rod.darktech.org is already known as master server. Please continue to add any slave servers, one per line. When you are done with the list, type a <control D>. master server : ellington next host to add: coltrane next host to add: ^D The current list of NIS servers looks like this: ellington coltrane Is this correct? [y/n: y] y [..output from map generation..] NIS Map update completed. ellington has been setup as an YP master server without any errors. ypinit should have created /var/yp/Makefile from /var/yp/Makefile.dist. When created, this file assumes that you are operating in a single server NIS environment with only FreeBSD machines. Since test-domain has a slave server as well, you must edit /var/yp/Makefile: ellington&prompt.root; vi /var/yp/Makefile You should comment out the line that says NOPUSH = "True" (if it is not commented out already). Setting up a NIS Slave Server NIS slave server Setting up an NIS slave server is even more simple than setting up the master. Log on to the slave server and edit the file /etc/rc.conf as you did before. The only difference is that we now must use the option when running ypinit. The option requires the name of the NIS master be passed to it as well, so our command line looks like: coltrane&prompt.root; ypinit -s ellington test-domain Server Type: SLAVE Domain: test-domain Master: ellington Creating an YP server will require that you answer a few questions. Questions will all be asked at the beginning of the procedure. Do you want this procedure to quit on non-fatal errors? [y/n: n] n Ok, please remember to go back and redo manually whatever fails. If you don't, something might not work. There will be no further questions. The remainder of the procedure should take a few minutes, to copy the databases from ellington. Transferring netgroup... ypxfr: Exiting: Map successfully transferred Transferring netgroup.byuser... ypxfr: Exiting: Map successfully transferred Transferring netgroup.byhost... ypxfr: Exiting: Map successfully transferred Transferring master.passwd.byuid... ypxfr: Exiting: Map successfully transferred Transferring passwd.byuid... ypxfr: Exiting: Map successfully transferred Transferring passwd.byname... ypxfr: Exiting: Map successfully transferred Transferring group.bygid... ypxfr: Exiting: Map successfully transferred Transferring group.byname... ypxfr: Exiting: Map successfully transferred Transferring services.byname... ypxfr: Exiting: Map successfully transferred Transferring rpc.bynumber... ypxfr: Exiting: Map successfully transferred Transferring rpc.byname... ypxfr: Exiting: Map successfully transferred Transferring protocols.byname... ypxfr: Exiting: Map successfully transferred Transferring master.passwd.byname... ypxfr: Exiting: Map successfully transferred Transferring networks.byname... ypxfr: Exiting: Map successfully transferred Transferring networks.byaddr... ypxfr: Exiting: Map successfully transferred Transferring netid.byname... ypxfr: Exiting: Map successfully transferred Transferring hosts.byaddr... ypxfr: Exiting: Map successfully transferred Transferring protocols.bynumber... ypxfr: Exiting: Map successfully transferred Transferring ypservers... ypxfr: Exiting: Map successfully transferred Transferring hosts.byname... ypxfr: Exiting: Map successfully transferred coltrane has been setup as an YP slave server without any errors. Don't forget to update map ypservers on ellington. You should now have a directory called /var/yp/test-domain. Copies of the NIS master server's maps should be in this directory. You will need to make sure that these stay updated. The following /etc/crontab entries on your slave servers should do the job: 20 * * * * root /usr/libexec/ypxfr passwd.byname 21 * * * * root /usr/libexec/ypxfr passwd.byuid These two lines force the slave to sync its maps with the maps on the master server. Although these entries are not mandatory, since the master server attempts to ensure any changes to its NIS maps are communicated to its slaves and because password information is vital to systems depending on the server, it is a good idea to force the updates. This is more important on busy networks where map updates might not always complete. Now, run the command /etc/netstart on the slave server as well, which again starts the NIS server. NIS Clients An NIS client establishes what is called a binding to a particular NIS server using the ypbind daemon. ypbind checks the system's default domain (as set by the domainname command), and begins broadcasting RPC requests on the local network. These requests specify the name of the domain for which ypbind is attempting to establish a binding. If a server that has been configured to serve the requested domain receives one of the broadcasts, it will respond to ypbind, which will record the server's address. If there are several servers available (a master and several slaves, for example), ypbind will use the address of the first one to respond. From that point on, the client system will direct all of its NIS requests to that server. ypbind will occasionally ping the server to make sure it is still up and running. If it fails to receive a reply to one of its pings within a reasonable amount of time, ypbind will mark the domain as unbound and begin broadcasting again in the hopes of locating another server. Setting Up a NIS Client NIS client configuration Setting up a FreeBSD machine to be a NIS client is fairly straightforward. Edit the file /etc/rc.conf and add the following lines in order to set the NIS domainname and start ypbind upon network startup: nisdomainname="test-domain" nis_client_enable="YES" To import all possible password entries from the NIS server, remove all user accounts from your /etc/master.passwd file and use vipw to add the following line to the end of the file: +::::::::: This line will afford anyone with a valid account in the NIS server's password maps an account. There are many ways to configure your NIS client by changing this line. See the netgroups section below for more information. For more detailed reading see O'Reilly's book on Managing NFS and NIS. You should keep at least one local account (i.e. not imported via NIS) in your /etc/master.passwd and this account should also be a member of the group wheel. If there is something wrong with NIS, this account can be used to log in remotely, become root, and fix things. To import all possible group entries from the NIS server, add this line to your /etc/group file: +:*:: After completing these steps, you should be able to run ypcat passwd and see the NIS server's passwd map. NIS Security In general, any remote user can issue an RPC to &man.ypserv.8; and retrieve the contents of your NIS maps, provided the remote user knows your domainname. To prevent such unauthorized transactions, &man.ypserv.8; supports a feature called securenets which can be used to restrict access to a given set of hosts. At startup, &man.ypserv.8; will attempt to load the securenets information from a file called /var/yp/securenets. This path varies depending on the path specified with the option. This file contains entries that consist of a network specification and a network mask separated by white space. Lines starting with # are considered to be comments. A sample securenets file might look like this: # allow connections from local host -- mandatory 127.0.0.1 255.255.255.255 # allow connections from any host # on the 192.168.128.0 network 192.168.128.0 255.255.255.0 # allow connections from any host # between 10.0.0.0 to 10.0.15.255 # this includes the machines in the testlab 10.0.0.0 255.255.240.0 If &man.ypserv.8; receives a request from an address that matches one of these rules, it will process the request normally. If the address fails to match a rule, the request will be ignored and a warning message will be logged. If the /var/yp/securenets file does not exist, ypserv will allow connections from any host. The ypserv program also has support for Wietse Venema's tcpwrapper package. This allows the administrator to use the tcpwrapper configuration files for access control instead of /var/yp/securenets. While both of these access control mechanisms provide some security, they, like the privileged port test, are vulnerable to IP spoofing attacks. All NIS-related traffic should be blocked at your firewall. Servers using /var/yp/securenets may fail to serve legitimate NIS clients with archaic TCP/IP implementations. Some of these implementations set all host bits to zero when doing broadcasts and/or fail to observe the subnet mask when calculating the broadcast address. While some of these problems can be fixed by changing the client configuration, other problems may force the retirement of the client systems in question or the abandonment of /var/yp/securenets. Using /var/yp/securenets on a server with such an archaic implementation of TCP/IP is a really bad idea and will lead to loss of NIS functionality for large parts of your network. tcpwrapper The use of the tcpwrapper package increases the latency of your NIS server. The additional delay may be long enough to cause timeouts in client programs, especially in busy networks or with slow NIS servers. If one or more of your client systems suffers from these symptoms, you should convert the client systems in question into NIS slave servers and force them to bind to themselves. Barring Some Users from Logging On In our lab, there is a machine basie that is supposed to be a faculty only workstation. We do not want to take this machine out of the NIS domain, yet the passwd file on the master NIS server contains accounts for both faculty and students. What can we do? There is a way to bar specific users from logging on to a machine, even if they are present in the NIS database. To do this, all you must do is add -username to the end of the /etc/master.passwd file on the client machine, where username is the username of the user you wish to bar from logging in. This should preferably be done using vipw, since vipw will sanity check your changes to /etc/master.passwd, as well as automatically rebuild the password database when you finish editing. For example, if we wanted to bar user bill from logging on to basie we would: basie&prompt.root; vipw [add -bill to the end, exit] vipw: rebuilding the database... vipw: done basie&prompt.root; cat /etc/master.passwd root:[password]:0:0::0:0:The super-user:/root:/bin/csh toor:[password]:0:0::0:0:The other super-user:/root:/bin/sh daemon:*:1:1::0:0:Owner of many system processes:/root:/sbin/nologin operator:*:2:5::0:0:System &:/:/sbin/nologin bin:*:3:7::0:0:Binaries Commands and Source,,,:/:/sbin/nologin tty:*:4:65533::0:0:Tty Sandbox:/:/sbin/nologin kmem:*:5:65533::0:0:KMem Sandbox:/:/sbin/nologin games:*:7:13::0:0:Games pseudo-user:/usr/games:/sbin/nologin news:*:8:8::0:0:News Subsystem:/:/sbin/nologin man:*:9:9::0:0:Mister Man Pages:/usr/share/man:/sbin/nologin bind:*:53:53::0:0:Bind Sandbox:/:/sbin/nologin uucp:*:66:66::0:0:UUCP pseudo-user:/var/spool/uucppublic:/usr/libexec/uucp/uucico xten:*:67:67::0:0:X-10 daemon:/usr/local/xten:/sbin/nologin pop:*:68:6::0:0:Post Office Owner:/nonexistent:/sbin/nologin nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/sbin/nologin +::::::::: -bill basie&prompt.root; Udo Erdelhoff Contributed by Using Netgroups netgroups The method shown in the previous section works reasonably well if you need special rules for a very small number of users and/or machines. On larger networks, you will forget to bar some users from logging onto sensitive machines, or you may even have to modify each machine separately, thus losing the main benefit of NIS, centralized administration. The NIS developers' solution for this problem is called netgroups. Their purpose and semantics can be compared to the normal groups used by &unix; file systems. The main differences are the lack of a numeric id and the ability to define a netgroup by including both user accounts and other netgroups. Netgroups were developed to handle large, complex networks with hundreds of users and machines. On one hand, this is a Good Thing if you are forced to deal with such a situation. On the other hand, this complexity makes it almost impossible to explain netgroups with really simple examples. The example used in the remainder of this section demonstrates this problem. Let us assume that your successful introduction of NIS in your laboratory caught your superiors' interest. Your next job is to extend your NIS domain to cover some of the other machines on campus. The two tables contain the names of the new users and new machines as well as brief descriptions of them. User Name(s) Description alpha, beta Normal employees of the IT department charlie, delta The new apprentices of the IT department echo, foxtrott, golf, ... Ordinary employees able, baker, ... The current interns Machine Name(s) Description war, death, famine, pollution Your most important servers. Only the IT employees are allowed to log onto these machines. pride, greed, envy, wrath, lust, sloth Less important servers. All members of the IT department are allowed to login onto these machines. one, two, three, four, ... Ordinary workstations. Only the real employees are allowed to use these machines. trashcan A very old machine without any critical data. Even the intern is allowed to use this box. If you tried to implement these restrictions by separately blocking each user, you would have to add one -user line to each system's passwd for each user who is not allowed to login onto that system. If you forget just one entry, you could be in trouble. It may be feasible to do this correctly during the initial setup, however you will eventually forget to add the lines for new users during day-to-day operations. After all, Murphy was an optimist. Handling this situation with netgroups offers several advantages. Each user need not be handled separately; you assign a user to one or more netgroups and allow or forbid logins for all members of the netgroup. If you add a new machine, you will only have to define login restrictions for netgroups. If a new user is added, you will only have to add the user to one or more netgroups. Those changes are independent of each other; no more for each combination of user and machine do... If your NIS setup is planned carefully, you will only have to modify exactly one central configuration file to grant or deny access to machines. The first step is the initialization of the NIS map netgroup. FreeBSD's &man.ypinit.8; does not create this map by default, but its NIS implementation will support it once it has been created. To create an empty map, simply type ellington&prompt.root; vi /var/yp/netgroup and start adding content. For our example, we need at least four netgroups: IT employees, IT apprentices, normal employees and interns. IT_EMP (,alpha,test-domain) (,beta,test-domain) IT_APP (,charlie,test-domain) (,delta,test-domain) USERS (,echo,test-domain) (,foxtrott,test-domain) \ (,golf,test-domain) INTERNS (,able,test-domain) (,baker,test-domain) IT_EMP, IT_APP etc. are the names of the netgroups. Each bracketed group adds one or more user accounts to it. The three fields inside a group are: The name of the host(s) where the following items are valid. If you do not specify a hostname, the entry is valid on all hosts. If you do specify a hostname, you will enter a realm of darkness, horror and utter confusion. The name of the account that belongs to this netgroup. The NIS domain for the account. You can import accounts from other NIS domains into your netgroup if you are one of the unlucky fellows with more than one NIS domain. Each of these fields can contain wildcards. See &man.netgroup.5; for details. netgroups Netgroup names longer than 8 characters should not be used, especially if you have machines running other operating systems within your NIS domain. The names are case sensitive; using capital letters for your netgroup names is an easy way to distinguish between user, machine and netgroup names. Some NIS clients (other than FreeBSD) cannot handle netgroups with a large number of entries. For example, some older versions of &sunos; start to cause trouble if a netgroup contains more than 15 entries. You can circumvent this limit by creating several sub-netgroups with 15 users or less and a real netgroup that consists of the sub-netgroups: BIGGRP1 (,joe1,domain) (,joe2,domain) (,joe3,domain) [...] BIGGRP2 (,joe16,domain) (,joe17,domain) [...] BIGGRP3 (,joe31,domain) (,joe32,domain) BIGGROUP BIGGRP1 BIGGRP2 BIGGRP3 You can repeat this process if you need more than 225 users within a single netgroup. Activating and distributing your new NIS map is easy: ellington&prompt.root; cd /var/yp ellington&prompt.root; make This will generate the three NIS maps netgroup, netgroup.byhost and netgroup.byuser. Use &man.ypcat.1; to check if your new NIS maps are available: ellington&prompt.user; ypcat -k netgroup ellington&prompt.user; ypcat -k netgroup.byhost ellington&prompt.user; ypcat -k netgroup.byuser The output of the first command should resemble the contents of /var/yp/netgroup. The second command will not produce output if you have not specified host-specific netgroups. The third command can be used to get the list of netgroups for a user. The client setup is quite simple. To configure the server war, you only have to start &man.vipw.8; and replace the line +::::::::: with +@IT_EMP::::::::: Now, only the data for the users defined in the netgroup IT_EMP is imported into war's password database and only these users are allowed to login. Unfortunately, this limitation also applies to the ~ function of the shell and all routines converting between user names and numerical user IDs. In other words, cd ~user will not work, ls -l will show the numerical id instead of the username and find . -user joe -print will fail with No such user. To fix this, you will have to import all user entries without allowing them to login onto your servers. This can be achieved by adding another line to /etc/master.passwd. This line should contain: +:::::::::/sbin/nologin, meaning Import all entries but replace the shell with /sbin/nologin in the imported entries. You can replace any field in the passwd entry by placing a default value in your /etc/master.passwd. Make sure that the line +:::::::::/sbin/nologin is placed after +@IT_EMP:::::::::. Otherwise, all user accounts imported from NIS will have /sbin/nologin as their login shell. After this change, you will only have to change one NIS map if a new employee joins the IT department. You could use a similar approach for the less important servers by replacing the old +::::::::: in their local version of /etc/master.passwd with something like this: +@IT_EMP::::::::: +@IT_APP::::::::: +:::::::::/sbin/nologin The corresponding lines for the normal workstations could be: +@IT_EMP::::::::: +@USERS::::::::: +:::::::::/sbin/nologin And everything would be fine until there is a policy change a few weeks later: The IT department starts hiring interns. The IT interns are allowed to use the normal workstations and the less important servers; and the IT apprentices are allowed to login onto the main servers. You add a new netgroup IT_INTERN, add the new IT interns to this netgroup and start to change the config on each and every machine... As the old saying goes: Errors in centralized planning lead to global mess. NIS' ability to create netgroups from other netgroups can be used to prevent situations like these. One possibility is the creation of role-based netgroups. For example, you could create a netgroup called BIGSRV to define the login restrictions for the important servers, another netgroup called SMALLSRV for the less important servers and a third netgroup called USERBOX for the normal workstations. Each of these netgroups contains the netgroups that are allowed to login onto these machines. The new entries for your NIS map netgroup should look like this: BIGSRV IT_EMP IT_APP SMALLSRV IT_EMP IT_APP ITINTERN USERBOX IT_EMP ITINTERN USERS This method of defining login restrictions works reasonably well if you can define groups of machines with identical restrictions. Unfortunately, this is the exception and not the rule. Most of the time, you will need the ability to define login restrictions on a per-machine basis. Machine-specific netgroup definitions are the other possibility to deal with the policy change outlined above. In this scenario, the /etc/master.passwd of each box contains two lines starting with +. The first of them adds a netgroup with the accounts allowed to login onto this machine, the second one adds all other accounts with /sbin/nologin as shell. It is a good idea to use the ALL-CAPS version of the machine name as the name of the netgroup. In other words, the lines should look like this: +@BOXNAME::::::::: +:::::::::/sbin/nologin Once you have completed this task for all your machines, you will not have to modify the local versions of /etc/master.passwd ever again. All further changes can be handled by modifying the NIS map. Here is an example of a possible netgroup map for this scenario with some additional goodies. # Define groups of users first IT_EMP (,alpha,test-domain) (,beta,test-domain) IT_APP (,charlie,test-domain) (,delta,test-domain) DEPT1 (,echo,test-domain) (,foxtrott,test-domain) DEPT2 (,golf,test-domain) (,hotel,test-domain) DEPT3 (,india,test-domain) (,juliet,test-domain) ITINTERN (,kilo,test-domain) (,lima,test-domain) D_INTERNS (,able,test-domain) (,baker,test-domain) # # Now, define some groups based on roles USERS DEPT1 DEPT2 DEPT3 BIGSRV IT_EMP IT_APP SMALLSRV IT_EMP IT_APP ITINTERN USERBOX IT_EMP ITINTERN USERS # # And a groups for a special tasks # Allow echo and golf to access our anti-virus-machine SECURITY IT_EMP (,echo,test-domain) (,golf,test-domain) # # machine-based netgroups # Our main servers WAR BIGSRV FAMINE BIGSRV # User india needs access to this server POLLUTION BIGSRV (,india,test-domain) # # This one is really important and needs more access restrictions DEATH IT_EMP # # The anti-virus-machine mentioned above ONE SECURITY # # Restrict a machine to a single user TWO (,hotel,test-domain) # [...more groups to follow] If you are using some kind of database to manage your user accounts, you should be able to create the first part of the map with your database's report tools. This way, new users will automatically have access to the boxes. One last word of caution: It may not always be advisable to use machine-based netgroups. If you are deploying a couple of dozen or even hundreds of identical machines for student labs, you should use role-based netgroups instead of machine-based netgroups to keep the size of the NIS map within reasonable limits. Important Things to Remember There are still a couple of things that you will need to do differently now that you are in an NIS environment. Every time you wish to add a user to the lab, you must add it to the master NIS server only, and you must remember to rebuild the NIS maps. If you forget to do this, the new user will not be able to login anywhere except on the NIS master. For example, if we needed to add a new user jsmith to the lab, we would: &prompt.root; pw useradd jsmith &prompt.root; cd /var/yp &prompt.root; make test-domain You could also run adduser jsmith instead of pw useradd jsmith. Keep the administration accounts out of the NIS maps. You do not want to be propagating administrative accounts and passwords to machines that will have users that should not have access to those accounts. Keep the NIS master and slave secure, and minimize their downtime. If somebody either hacks or simply turns off these machines, they have effectively rendered many people without the ability to login to the lab. This is the chief weakness of any centralized administration system. If you do not protect your NIS servers, you will have a lot of angry users! NIS v1 Compatibility FreeBSD's ypserv has some support for serving NIS v1 clients. FreeBSD's NIS implementation only uses the NIS v2 protocol, however other implementations include support for the v1 protocol for backwards compatibility with older systems. The ypbind daemons supplied with these systems will try to establish a binding to an NIS v1 server even though they may never actually need it (and they may persist in broadcasting in search of one even after they receive a response from a v2 server). Note that while support for normal client calls is provided, this version of ypserv does not handle v1 map transfer requests; consequently, it cannot be used as a master or slave in conjunction with older NIS servers that only support the v1 protocol. Fortunately, there probably are not any such servers still in use today. NIS Servers That Are Also NIS Clients Care must be taken when running ypserv in a multi-server domain where the server machines are also NIS clients. It is generally a good idea to force the servers to bind to themselves rather than allowing them to broadcast bind requests and possibly become bound to each other. Strange failure modes can result if one server goes down and others are dependent upon it. Eventually all the clients will time out and attempt to bind to other servers, but the delay involved can be considerable and the failure mode is still present since the servers might bind to each other all over again. You can force a host to bind to a particular server by running ypbind with the flag. If you do not want to do this manually each time you reboot your NIS server, you can add the following lines to your /etc/rc.conf: nis_client_enable="YES" # run client stuff as well nis_client_flags="-S NIS domain,server" See &man.ypbind.8; for further information. Password Formats NIS password formats One of the most common issues that people run into when trying to implement NIS is password format compatibility. If your NIS server is using DES encrypted passwords, it will only support clients that are also using DES. For example, if you have &solaris; NIS clients in your network, then you will almost certainly need to use DES encrypted passwords. To check which format your servers and clients are using, look at /etc/login.conf. If the host is configured to use DES encrypted passwords, then the default class will contain an entry like this: default:\ :passwd_format=des:\ :copyright=/etc/COPYRIGHT:\ [Further entries elided] Other possible values for the passwd_format capability include blf and md5 (for Blowfish and MD5 encrypted passwords, respectively). If you have made changes to /etc/login.conf, you will also need to rebuild the login capability database, which is achieved by running the following command as root: &prompt.root; cap_mkdb /etc/login.conf The format of passwords already in /etc/master.passwd will not be updated until a user changes their password for the first time after the login capability database is rebuilt. Next, in order to ensure that passwords are encrypted with the format that you have chosen, you should also check that the crypt_default in /etc/auth.conf gives precedence to your chosen password format. To do this, place the format that you have chosen first in the list. For example, when using DES encrypted passwords, the entry would be: crypt_default = des blf md5 Having followed the above steps on each of the &os; based NIS servers and clients, you can be sure that they all agree on which password format is used within your network. If you have trouble authenticating on an NIS client, this is a pretty good place to start looking for possible problems. Remember: if you want to deploy an NIS server for a heterogenous network, you will probably have to use DES on all systems because it is the lowest common standard. Greg Sutter Written by DHCP What Is DHCP? Dynamic Host Configuration Protocol DHCP Internet Software Consortium (ISC) DHCP, the Dynamic Host Configuration Protocol, describes the means by which a system can connect to a network and obtain the necessary information for communication upon that network. FreeBSD uses the ISC (Internet Software Consortium) DHCP implementation, so all implementation-specific information here is for use with the ISC distribution. What This Section Covers This section describes both the client-side and server-side components of the ISC DHCP system. The client-side program, dhclient, comes integrated within FreeBSD, and the server-side portion is available from the net/isc-dhcp3-server port. The &man.dhclient.8;, &man.dhcp-options.5;, and &man.dhclient.conf.5; manual pages, in addition to the references below, are useful resources. How It Works UDP When dhclient, the DHCP client, is executed on the client machine, it begins broadcasting requests for configuration information. By default, these requests are on UDP port 68. The server replies on UDP 67, giving the client an IP address and other relevant network information such as netmask, router, and DNS servers. All of this information comes in the form of a DHCP lease and is only valid for a certain time (configured by the DHCP server maintainer). In this manner, stale IP addresses for clients no longer connected to the network can be automatically reclaimed. DHCP clients can obtain a great deal of information from the server. An exhaustive list may be found in &man.dhcp-options.5;. FreeBSD Integration FreeBSD fully integrates the ISC DHCP client, dhclient. DHCP client support is provided within both the installer and the base system, obviating the need for detailed knowledge of network configurations on any network that runs a DHCP server. dhclient has been included in all FreeBSD distributions since 3.2. sysinstall DHCP is supported by sysinstall. When configuring a network interface within sysinstall, the first question asked is, Do you want to try DHCP configuration of this interface? Answering affirmatively will execute dhclient, and if successful, will fill in the network configuration information automatically. There are two things you must do to have your system use DHCP upon startup: DHCP requirements Make sure that the bpf device is compiled into your kernel. To do this, add pseudo-device bpf to your kernel configuration file, and rebuild the kernel. For more information about building kernels, see . The bpf device is already part of the GENERIC kernel that is supplied with FreeBSD, so if you do not have a custom kernel, you should not need to create one in order to get DHCP working. For those who are particularly security conscious, you should be warned that bpf is also the device that allows packet sniffers to work correctly (although they still have to be run as root). bpf is required to use DHCP, but if you are very sensitive about security, you probably should not add bpf to your kernel in the expectation that at some point in the future you will be using DHCP. Edit your /etc/rc.conf to include the following: ifconfig_fxp0="DHCP" Be sure to replace fxp0 with the designation for the interface that you wish to dynamically configure, as described in . If you are using a different location for dhclient, or if you wish to pass additional flags to dhclient, also include the following (editing as necessary): dhcp_program="/sbin/dhclient" dhcp_flags="" DHCP server The DHCP server, dhcpd, is included as part of the net/isc-dhcp3-server port in the ports collection. This port contains the ISC DHCP server and documentation. Files DHCP configuration files /etc/dhclient.conf dhclient requires a configuration file, /etc/dhclient.conf. Typically the file contains only comments, the defaults being reasonably sane. This configuration file is described by the &man.dhclient.conf.5; manual page. /sbin/dhclient dhclient is statically linked and resides in /sbin. The &man.dhclient.8; manual page gives more information about dhclient. /sbin/dhclient-script dhclient-script is the FreeBSD-specific DHCP client configuration script. It is described in &man.dhclient-script.8;, but should not need any user modification to function properly. /var/db/dhclient.leases The DHCP client keeps a database of valid leases in this file, which is written as a log. &man.dhclient.leases.5; gives a slightly longer description. Further Reading The DHCP protocol is fully described in RFC 2131. An informational resource has also been set up at dhcp.org. Installing and Configuring a DHCP Server What This Section Covers This section provides information on how to configure a FreeBSD system to act as a DHCP server using the ISC (Internet Software Consortium) implementation of the DHCP suite. The server portion of the suite is not provided as part of FreeBSD, and so you will need to install the net/isc-dhcp3-server port to provide this service. See for more information on using the ports collection. DHCP Server Installation DHCP installation In order to configure your FreeBSD system as a DHCP server, you will need to ensure that the &man.bpf.4; device is compiled into your kernel. To do this, add pseudo-device bpf to your kernel configuration file, and rebuild the kernel. For more information about building kernels, see . The bpf device is already part of the GENERIC kernel that is supplied with FreeBSD, so you do not need to create a custom kernel in order to get DHCP working. Those who are particularly security conscious should note that bpf is also the device that allows packet sniffers to work correctly (although such programs still need privileged access). bpf is required to use DHCP, but if you are very sensitive about security, you probably should not include bpf in your kernel purely because you expect to use DHCP at some point in the future. The next thing that you will need to do is edit the sample dhcpd.conf which was installed by the net/isc-dhcp3-server port. By default, this will be /usr/local/etc/dhcpd.conf.sample, and you should copy this to /usr/local/etc/dhcpd.conf before proceeding to make changes. Configuring the DHCP Server DHCP dhcpd.conf dhcpd.conf is comprised of declarations regarding subnets and hosts, and is perhaps most easily explained using an example : option domain-name "example.com"; option domain-name-servers 192.168.4.100; option subnet-mask 255.255.255.0; default-lease-time 3600; max-lease-time 86400; ddns-update-style none; subnet 192.168.4.0 netmask 255.255.255.0 { range 192.168.4.129 192.168.4.254; option routers 192.168.4.1; } host mailhost { hardware ethernet 02:03:04:05:06:07; fixed-address mailhost.example.com; } This option specifies the domain that will be provided to clients as the default search domain. See &man.resolv.conf.5; for more information on what this means. This option specifies a comma separated list of DNS servers that the client should use. The netmask that will be provided to clients. A client may request a specific length of time that a lease will be valid. Otherwise the server will assign a lease with this expiry value (in seconds). This is the maximum length of time that the server will lease for. Should a client request a longer lease, a lease will be issued, although it will only be valid for max-lease-time seconds. This option specifies whether the DHCP server should attempt to update DNS when a lease is accepted or released. In the ISC implementation, this option is required. This denotes which IP addresses should be used in the pool reserved for allocating to clients. IP addresses between, and including, the ones stated are handed out to clients. Declares the default gateway that will be provided to clients. The hardware MAC address of a host (so that the DHCP server can recognize a host when it makes a request). Specifies that the host should always be given the same IP address. Note that a hostname is OK here, since the DHCP server will resolve the hostname itself before returning the lease information. Once you have finished writing your dhcpd.conf, you can proceed to start the server by issuing the following command: &prompt.root; /usr/local/etc/rc.d/isc-dhcpd.sh start Should you need to make changes to the configuration of your server in the future, it is important to note that sending a SIGHUP signal to dhcpd does not result in the configuration being reloaded, as it does with most daemons. You will need to send a SIGTERM signal to stop the process, and then restart it using the command above. Files DHCP configuration files /usr/local/sbin/dhcpd dhcpd is statically linked and resides in /usr/local/sbin. The &man.dhcpd.8; manual page installed with the port gives more information about dhcpd. /usr/local/etc/dhcpd.conf dhcpd requires a configuration file, /usr/local/etc/dhcpd.conf before it will start providing service to clients. This file needs to contain all the information that should be provided to clients that are being serviced, along with information regarding the operation of the server. This configuration file is described by the &man.dhcpd.conf.5; manual page installed by the port. /var/db/dhcpd.leases The DHCP server keeps a database of leases it has issued in this file, which is written as a log. The manual page &man.dhcpd.leases.5;, installed by the port gives a slightly longer description. /usr/local/sbin/dhcrelay dhcrelay is used in advanced environments where one DHCP server forwards a request from a client to another DHCP server on a separate network. If you require this functionality, then install the net/isc-dhcp3-server port. The &man.dhcrelay.8; manual page provided with the port contains more detail. Chern Lee Contributed by DNS Overview BIND FreeBSD utilizes, by default, a version of BIND (Berkeley Internet Name Domain), which is the most common implementation of the DNS protocol. DNS is the protocol through which names are mapped to IP addresses, and vice versa. For example, a query for www.FreeBSD.org will receive a reply with the IP address of The FreeBSD Project's web server, whereas, a query for ftp.FreeBSD.org will return the IP address of the corresponding FTP machine. Likewise, the opposite can happen. A query for an IP address can resolve its hostname. It is not necessary to run a name server to perform DNS lookups on a system. DNS DNS is coordinated across the Internet through a somewhat complex system of authoritative root name servers, and other smaller-scale name servers who host and cache individual domain information. This document refers to BIND 8.x, as it is the stable version used in FreeBSD. BIND 9.x in FreeBSD can be installed through the net/bind9 port. RFC1034 and RFC1035 dictate the DNS protocol. Currently, BIND is maintained by the Internet Software Consortium (www.isc.org). Terminology To understand this document, some terms related to DNS must be understood. Term Definition Forward DNS Mapping of hostnames to IP addresses Origin Refers to the domain covered in a particular zone file named, BIND, name server Common names for the BIND name server package within FreeBSD resolver Resolver A system process through which a machine queries a name server for zone information reverse DNS Reverse DNS The opposite of forward DNS; mapping of IP addresses to hostnames root zone Root zone The beginning of the Internet zone hierarchy. All zones fall under the root zone, similar to how all files in a file system fall under the root directory. Zone An individual domain, subdomain, or portion of the DNS administered by the same authority zones examples Examples of zones: . is the root zone org. is a zone under the root zone example.org is a zone under the org. zone foo.example.org. is a subdomain, a zone under the example.org. zone 1.2.3.in-addr.arpa is a zone referencing all IP addresses which fall under the 3.2.1.* IP space. As one can see, the more specific part of a hostname appears to its left. For example, example.org. is more specific than org., as org. is more specific than the root zone. The layout of each part of a hostname is much like a filesystem: the /dev directory falls within the root, and so on. Reasons to Run a Name Server Name servers usually come in two forms: an authoritative name server, and a caching name server. An authoritative name server is needed when: one wants to serve DNS information to the world, replying authoritatively to queries. a domain, such as example.org, is registered and IP addresses need to be assigned to hostnames under it. an IP address block requires reverse DNS entries (IP to hostname). a backup name server, called a slave, must reply to queries when the primary is down or inaccessible. A caching name server is needed when: a local DNS server may cache and respond more quickly than querying an outside name server. a reduction in overall network traffic is desired (DNS traffic has been measured to account for 5% or more of total Internet traffic). When one queries for www.FreeBSD.org, the resolver usually queries the uplink ISP's name server, and retrieves the reply. With a local, caching DNS server, the query only has to be made once to the outside world by the caching DNS server. Every additional query will not have to look to the outside of the local network, since the information is cached locally. How It Works In FreeBSD, the BIND daemon is called named for obvious reasons. File Description named the BIND daemon ndc name daemon control program /etc/namedb directory where BIND zone information resides /etc/namedb/named.conf daemon configuration file Zone files are usually contained within the /etc/namedb directory, and contain the DNS zone information served by the name server. Starting BIND BIND starting Since BIND is installed by default, configuring it all is relatively simple. To ensure the named daemon is started at boot, put the following modifications in /etc/rc.conf: named_enable="YES" To start the daemon manually (after configuring it) &prompt.root; ndc start Configuration Files BIND configuration files Using <command>make-localhost</command> Be sure to: &prompt.root; cd /etc/namedb &prompt.root; sh make-localhost to properly create the local reverse DNS zone file in /etc/namedb/localhost.rev. <filename>/etc/namedb/named.conf</filename> // $FreeBSD$ // // Refer to the named(8) manual page for details. If you are ever going // to setup a primary server, make sure you've understood the hairy // details of how DNS is working. Even with simple mistakes, you can // break connectivity for affected parties, or cause huge amount of // useless Internet traffic. options { directory "/etc/namedb"; // In addition to the "forwarders" clause, you can force your name // server to never initiate queries of its own, but always ask its // forwarders only, by enabling the following line: // // forward only; // If you've got a DNS server around at your upstream provider, enter // its IP address here, and enable the line below. This will make you // benefit from its cache, thus reduce overall DNS traffic in the Internet. /* forwarders { 127.0.0.1; }; */ Just as the comment says, to benefit from an uplink's cache, forwarders can be enabled here. Under normal circumstances, a name server will recursively query the Internet looking at certain name servers until it finds the answer it is looking for. Having this enabled will have it query the uplink's name server (or name server provided) first, taking advantage of its cache. If the uplink name server in question is a heavily trafficked, fast name server, enabling this may be worthwhile. 127.0.0.1 will not work here. Change this IP address to a name server at your uplink. /* * If there is a firewall between you and name servers you want * to talk to, you might need to uncomment the query-source * directive below. Previous versions of BIND always asked * questions using port 53, but BIND 8.1 uses an unprivileged * port by default. */ // query-source address * port 53; /* * If running in a sandbox, you may have to specify a different * location for the dumpfile. */ // dump-file "s/named_dump.db"; }; // Note: the following will be supported in a future release. /* host { any; } { topology { 127.0.0.0/8; }; }; */ // Setting up secondaries is way easier and the rough picture for this // is explained below. // // If you enable a local name server, don't forget to enter 127.0.0.1 // into your /etc/resolv.conf so this server will be queried first. // Also, make sure to enable it in /etc/rc.conf. zone "." { type hint; file "named.root"; }; zone "0.0.127.IN-ADDR.ARPA" { type master; file "localhost.rev"; }; zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.INT" { type master; file "localhost.rev"; }; // NB: Do not use the IP addresses below, they are faked, and only // serve demonstration/documentation purposes! // // Example secondary config entries. It can be convenient to become // a secondary at least for the zone where your own domain is in. Ask // your network administrator for the IP address of the responsible // primary. // // Never forget to include the reverse lookup (IN-ADDR.ARPA) zone! // (This is the first bytes of the respective IP address, in reverse // order, with ".IN-ADDR.ARPA" appended.) // // Before starting to setup a primary zone, better make sure you fully // understand how DNS and BIND works, however. There are sometimes // unobvious pitfalls. Setting up a secondary is comparably simpler. // // NB: Don't blindly enable the examples below. :-) Use actual names // and addresses instead. // // NOTE!!! FreeBSD runs bind in a sandbox (see named_flags in rc.conf). // The directory containing the secondary zones must be write accessible // to bind. The following sequence is suggested: // // mkdir /etc/namedb/s // chown bind:bind /etc/namedb/s // chmod 750 /etc/namedb/s For more information on running BIND in a sandbox, see Running named in a sandbox. /* zone "example.com" { type slave; file "s/example.com.bak"; masters { 192.168.1.1; }; }; zone "0.168.192.in-addr.arpa" { type slave; file "s/0.168.192.in-addr.arpa.bak"; masters { 192.168.1.1; }; }; */ In named.conf, these are examples of slave entries for a forward and reverse zone. For each new zone served, a new zone entry must be added to named.conf For example, the simplest zone entry for example.org can look like: zone "example.org" { type master; file "example.org"; }; The zone is a master, as indicated by the statement, holding its zone information in /etc/namedb/example.org indicated by the statement. zone "example.org" { type slave; file "example.org"; }; In the slave case, the zone information is transferred from the master name server for the particular zone, and saved in the file specified. If and when the master server dies or is unreachable, the slave name server will have the transferred zone information and will be able to serve it. Zone Files An example master zone file for example.org (existing within /etc/namedb/example.org) is as follows: $TTL 3600 example.org. IN SOA ns1.example.org. admin.example.org. ( 5 ; Serial 10800 ; Refresh 3600 ; Retry 604800 ; Expire 86400 ) ; Minimum TTL ; DNS Servers @ IN NS ns1.example.org. @ IN NS ns2.example.org. ; Machine Names localhost IN A 127.0.0.1 ns1 IN A 3.2.1.2 ns2 IN A 3.2.1.3 mail IN A 3.2.1.10 @ IN A 3.2.1.30 ; Aliases www IN CNAME @ ; MX Record @ IN MX 10 mail.example.org. Note that every hostname ending in a . is an exact hostname, whereas everything without a trailing . is referenced to the origin. For example, www is translated into www + origin. In our fictitious zone file, our origin is example.org., so www would translate to www.example.org. The format of a zone file follows: recordname IN recordtype value DNS records The most commonly used DNS records: SOA start of zone authority NS an authoritative name server A A host address CNAME the canonical name for an alias MX mail exchanger PTR a domain name pointer (used in reverse DNS) example.org. IN SOA ns1.example.org. admin.example.org. ( 5 ; Serial 10800 ; Refresh after 3 hours 3600 ; Retry after 1 hour 604800 ; Expire after 1 week 86400 ) ; Minimum TTL of 1 day example.org. the domain name, also the origin for this zone file. ns1.example.org. the primary/authoritative name server for this zone admin.example.org. the responsible person for this zone, email address with @ replaced. (admin@example.org becomes admin.example.org) 5 the serial number of the file. this must be incremented each time the zone file is modified. Nowadays, many admins prefer a yyyymmddrr format for the serial number. 2001041002 would mean last modified 04/10/2001, the latter 02 being the second time the zone file has been modified this day. The serial number is important as it alerts slave name servers for a zone when it is updated. @ IN NS ns1.example.org. This is an NS entry. Every name server that is going to reply authoritatively for the zone must have one of these entries. The @ as seen here could have been example.org. The @ translates to the origin. localhost IN A 127.0.0.1 ns1 IN A 3.2.1.2 ns2 IN A 3.2.1.3 mail IN A 3.2.1.10 @ IN A 3.2.1.30 The A record indicates machine names. As seen above, ns1.example.org would resolve to 3.2.1.2. Again, the origin symbol, @, is used here, thus meaning example.org would resolve to 3.2.1.30. www IN CNAME @ The canonical name record is usually used for giving aliases to a machine. In the example, www is aliased to the machine addressed to the origin, or example.org (3.2.1.30). CNAMEs can be used to provide alias hostnames, or round robin one hostname among multiple machines. + + MX record + + @ IN MX 10 mail.example.org. The MX record indicates which mail servers are responsible for handling incoming mail for the zone. mail.example.org is the hostname of the mail server, and 10 being the priority of that mail server. One can have several mail servers, with priorities of 3, 2, 1. A mail server attempting to deliver to example.org would first try the highest priority MX, then the second highest, etc, until the mail can be properly delivered. For in-addr.arpa zone files (reverse DNS), the same format is used, except with PTR entries instead of A or CNAME. $TTL 3600 1.2.3.in-addr.arpa. IN SOA ns1.example.org. admin.example.org. ( 5 ; Serial 10800 ; Refresh 3600 ; Retry 604800 ; Expire 3600 ) ; Minimum @ IN NS ns1.example.org. @ IN NS ns2.example.org. 2 IN PTR ns1.example.org. 3 IN PTR ns2.example.org. 10 IN PTR mail.example.org. 30 IN PTR example.org. This file gives the proper IP address to hostname mappings of our above fictitious domain. Caching Name Server BIND caching name server A caching name server is a name server that is not authoritative for any zones. It simply asks queries of its own, and remembers them for later use. To set one up, just configure the name server as usual, omitting any inclusions of zones. Running <application>named</application> in a Sandbox BIND running in a sandbox chroot For added security you may want to run &man.named.8; as an unprivileged user, and configure it to &man.chroot.8; into a sandbox directory. This makes everything outside of the sandbox inaccessible to the named daemon. Should named be compromised, this will help to reduce the damage that can be caused. By default, FreeBSD has a user and a group called bind, intended for this use. Various people would recommend that instead of configuring named to chroot, you should run named inside a &man.jail.8;. This section does not attempt to cover this situation. Since named will not be able to access anything outside of the sandbox (such as shared libraries, log sockets, and so on), there are a number of steps that need to be followed in order to allow named to function correctly. In the following checklist, it is assumed that the path to the sandbox is /etc/namedb and that you have made no prior modifications to the contents of this directory. Perform the following steps as root. Create all directories that named expects to see: &prompt.root; cd /etc/namedb &prompt.root; mkdir -p bin dev etc var/tmp var/run master slave &prompt.root; chown bind:bind slave var/* named only needs write access to these directories, so that is all we give it. Rearrange and create basic zone and configuration files: &prompt.root; cp /etc/localtime etc &prompt.root; mv named.conf etc && ln -sf etc/named.conf &prompt.root; mv named.root master &prompt.root; sh make-localhost && mv localhost.rev localhost-v6.rev master &prompt.root; cat > master/named.localhost $ORIGIN localhost. $TTL 6h @ IN SOA localhost. postmaster.localhost. ( 1 ; serial 3600 ; refresh 1800 ; retry 604800 ; expiration 3600 ) ; minimum IN NS localhost. IN A 127.0.0.1 ^D This allows named to log the correct time to &man.syslogd.8; If you are running a version of &os; prior to 4.9-RELEASE, build a statically linked copy of named-xfer, and copy it into the sandbox: &prompt.root; cd /usr/src/lib/libisc &prompt.root; make cleandir && make cleandir && make depend && make all &prompt.root; cd /usr/src/lib/libbind &prompt.root; make cleandir && make cleandir && make depend && make all &prompt.root; cd /usr/src/libexec/named-xfer &prompt.root; make cleandir && make cleandir && make depend && make NOSHARED=yes all &prompt.root; cp named-xfer /etc/namedb/bin && chmod 555 /etc/namedb/bin/named-xfer After your statically linked named-xfer is installed some cleaning up is required, to avoid leaving stale copies of libraries or programs in your source tree: &prompt.root; cd /usr/src/lib/libisc &prompt.root; make cleandir &prompt.root; cd /usr/src/lib/libbind &prompt.root; make cleandir &prompt.root; cd /usr/src/libexec/named-xfer &prompt.root; make cleandir This step has been reported to fail occasionally. If this happens to you, then issue the command: &prompt.root; cd /usr/src && make cleandir && make cleandir and delete your /usr/obj tree: &prompt.root; rm -fr /usr/obj && mkdir /usr/obj This will clean out any cruft from your source tree, and retrying the steps above should then work. If you are running &os; version 4.9-RELEASE or later, then the copy of named-xfer in /usr/libexec is statically linked by default, and you can simply use &man.cp.1; to copy it into your sandbox. Make a dev/null that named can see and write to: &prompt.root; cd /etc/namedb/dev && mknod null c 2 2 &prompt.root; chmod 666 null Symlink /var/run/ndc to /etc/namedb/var/run/ndc: &prompt.root; ln -sf /etc/namedb/var/run/ndc /var/run/ndc This simply avoids having to specify the option to &man.ndc.8; every time you run it. Since the contents of /var/run are deleted on boot, if this is something that you find useful you may wish to add this command to root's crontab, making use of the option. See &man.crontab.5; for more information regarding this. Configure &man.syslogd.8; to create an extra log socket that named can write to. To do this, add -l /etc/namedb/dev/log to the syslogd_flags variable in /etc/rc.conf. Arrange to have named start and chroot itself to the sandbox by adding the following to /etc/rc.conf: named_enable="YES" named_flags="-u bind -g bind -t /etc/namedb /etc/named.conf" Note that the configuration file /etc/named.conf is denoted by a full pathname relative to the sandbox, i.e. in the line above, the file referred to is actually /etc/namedb/etc/named.conf. The next step is to edit /etc/namedb/etc/named.conf so that named knows which zones to load and where to find them on the disk. There follows a commented example (anything not specifically commented here is no different from the setup for a DNS server not running in a sandbox): options { directory "/"; named-xfer "/bin/named-xfer"; version ""; // Don't reveal BIND version query-source address * port 53; }; // ndc control socket controls { unix "/var/run/ndc" perm 0600 owner 0 group 0; }; // Zones follow: zone "localhost" IN { type master; file "master/named.localhost"; allow-transfer { localhost; }; notify no; }; zone "0.0.127.in-addr.arpa" IN { type master; file "master/localhost.rev"; allow-transfer { localhost; }; notify no; }; zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.int" { type master; file "master/localhost-v6.rev"; allow-transfer { localhost; }; notify no; }; zone "." IN { type hint; file "master/named.root"; }; zone "private.example.net" in { type master; file "master/private.example.net.db"; allow-transfer { 192.168.10.0/24; }; }; zone "10.168.192.in-addr.arpa" in { type slave; masters { 192.168.10.2; }; file "slave/192.168.10.db"; }; The directory statement is specified as /, since all files that named needs are within this directory (recall that this is equivalent to a normal user's /etc/namedb. Specifies the full path to the named-xfer binary (from named's frame of reference). This is necessary since named is compiled to look for named-xfer in /usr/libexec by default. Specifies the filename (relative to the directory statement above) where named can find the zonefile for this zone. Specifies the filename (relative to the directory statement above) where named should write a copy of the zonefile for this zone after successfully transferring it from the master server. This is why we needed to change the ownership of the directory slave to bind in the setup stages above. After completing the steps above, either reboot your server or restart &man.syslogd.8; and start &man.named.8;, making sure to use the new options specified in syslogd_flags and named_flags. You should now be running a sandboxed copy of named! Security Although BIND is the most common implementation of DNS, there is always the issue of security. Possible and exploitable security holes are sometimes found. It is a good idea to subscribe to CERT and freebsd-security-notifications to stay up to date with the current Internet and FreeBSD security issues. If a problem arises, keeping sources up to date and having a fresh build of named would not hurt. Further Reading BIND/named manual pages: &man.ndc.8; &man.named.8; &man.named.conf.5; Official ISC Bind Page BIND FAQ O'Reilly DNS and BIND 4th Edition RFC1034 - Domain Names - Concepts and Facilities RFC1035 - Domain Names - Implementation and Specification Tom Hukins Contributed by NTP NTP Overview Over time, a computer's clock is prone to drift. As time passes, the computer's clock becomes less accurate. NTP (Network Time Protocol) is one way to ensure your clock is right. Many Internet services rely on, or greatly benefit from, computers' clocks being accurate. For example, a Web server may receive requests to send a file if it has modified since a certain time. Services such as &man.cron.8; run commands at a given time. If the clock is inaccurate, these commands may not run when expected. NTP ntpd FreeBSD ships with the &man.ntpd.8; NTP server which can be used to query other NTP servers to set the clock on your machine or provide time services to others. Choosing Appropriate NTP Servers NTP choosing servers In order to synchronize your clock, you will need to find one or more NTP servers to use. Your network administrator or ISP may have set up an NTP server for this purpose—check their documentation to see if this is the case. There is a list of publicly accessible NTP servers which you can use to find an NTP server near to you. Make sure you are aware of the policy for any servers you choose, and ask for permission if required. Choosing several unconnected NTP servers is a good idea in case one of the servers you are using becomes unreachable or its clock is unreliable. &man.ntpd.8; uses the responses it receives from other servers intelligently—it will favor unreliable servers less than reliable ones. Configuring Your Machine NTP configuration Basic Configuration ntpdate If you only wish to synchronize your clock when the machine boots up, you can use &man.ntpdate.8;. This may be appropriate for some desktop machines which are frequently rebooted and only require infrequent synchronization, but most machines should run &man.ntpd.8;. Using &man.ntpdate.8; at boot time is also a good idea for machines that run &man.ntpd.8;. The &man.ntpd.8; program changes the clock gradually, whereas &man.ntpdate.8; sets the clock, no matter how great the difference between a machine's current clock setting and the correct time. To enable &man.ntpdate.8; at boot time, add ntpdate_enable="YES" to /etc/rc.conf. You will also need to specify all servers you wish to synchronize with and any flags to be passed to &man.ntpdate.8; in ntpdate_flags. NTP ntp.conf General Configuration NTP is configured by the /etc/ntp.conf file in the format described in &man.ntp.conf.5;. Here is a simple example: server ntplocal.example.com prefer server timeserver.example.org server ntp2a.example.net driftfile /var/db/ntp.drift The server option specifies which servers are to be used, with one server listed on each line. If a server is specified with the prefer argument, as with ntplocal.example.com, that server is preferred over other servers. A response from a preferred server will be discarded if it differs significantly from other servers' responses, otherwise it will be used without any consideration to other responses. The prefer argument is normally used for NTP servers that are known to be highly accurate, such as those with special time monitoring hardware. The driftfile option specifies which file is used to store the system clock's frequency offset. The &man.ntpd.8; program uses this to automatically compensate for the clock's natural drift, allowing it to maintain a reasonably correct setting even if it is cut off from all external time sources for a period of time. The driftfile option specifies which file is used to store information about previous responses from the NTP servers you are using. This file contains internal information for NTP. It should not be modified by any other process. Controlling Access to Your Server By default, your NTP server will be accessible to all hosts on the Internet. The restrict option in /etc/ntp.conf allows you to control which machines can access your server. If you want to deny all machines from accessing your NTP server, add the following line to /etc/ntp.conf: restrict default ignore If you only want to allow machines within your own network to synchronize their clocks with your server, but ensure they are not allowed to configure the server or used as peers to synchronize against, add restrict 192.168.1.0 mask 255.255.255.0 notrust nomodify notrap instead, where 192.168.1.0 is an IP address on your network and 255.255.255.0 is your network's netmask. /etc/ntp.conf can contain multiple restrict options. For more details, see the Access Control Support subsection of &man.ntp.conf.5;. Running the NTP Server To ensure the NTP server is started at boot time, add the line xntpd_enable="YES" to /etc/rc.conf. If you wish to pass additional flags to &man.ntpd.8;, edit the xntpd_flags parameter in /etc/rc.conf. To start the server without rebooting your machine, run ntpd being sure to specify any additional parameters from xntpd_flags in /etc/rc.conf. For example: &prompt.root; ntpd -p /var/run/ntpd.pid Under &os; 5.X, various options in /etc/rc.conf have been renamed. Thus, you have to replace every instance of xntpd with ntpd in the options above. Using ntpd with a Temporary Internet Connection The &man.ntpd.8; program does not need a permanent connection to the Internet to function properly. However, if you have a temporary connection that is configured to dial out on demand, it is a good idea to prevent NTP traffic from triggering a dial out or keeping the connection alive. If you are using user PPP, you can use filter directives in /etc/ppp/ppp.conf. For example: set filter dial 0 deny udp src eq 123 # Prevent NTP traffic from initiating dial out set filter dial 1 permit 0 0 set filter alive 0 deny udp src eq 123 # Prevent incoming NTP traffic from keeping the connection open set filter alive 1 deny udp dst eq 123 # Prevent outgoing NTP traffic from keeping the connection open set filter alive 2 permit 0/0 0/0 For more details see the PACKET FILTERING section in &man.ppp.8; and the examples in /usr/share/examples/ppp/. Some Internet access providers block low-numbered ports, preventing NTP from functioning since replies never reach your machine. Further Information Documentation for the NTP server can be found in /usr/share/doc/ntp/ in HTML format. Chern Lee Contributed by Network Address Translation Overview natd FreeBSD's Network Address Translation daemon, commonly known as &man.natd.8; is a daemon that accepts incoming raw IP packets, changes the source to the local machine and re-injects these packets back into the outgoing IP packet stream. &man.natd.8; does this by changing the source IP address and port such that when data is received back, it is able to determine the original location of the data and forward it back to its original requester. Internet connection sharing IP masquerading The most common use of NAT is to perform what is commonly known as Internet Connection Sharing. Setup Due to the diminishing IP space in IPv4, and the increased number of users on high-speed consumer lines such as cable or DSL, people are increasingly in need of an Internet Connection Sharing solution. The ability to connect several computers online through one connection and IP address makes &man.natd.8; a reasonable choice. Most commonly, a user has a machine connected to a cable or DSL line with one IP address and wishes to use this one connected computer to provide Internet access to several more over a LAN. To do this, the FreeBSD machine on the Internet must act as a gateway. This gateway machine must have two NICs—one for connecting to the Internet router, the other connecting to a LAN. All the machines on the LAN are connected through a hub or switch. _______ __________ ________ | | | | | | | Hub |-----| Client B |-----| Router |----- Internet |_______| |__________| |________| | ____|_____ | | | Client A | |__________| Network Layout A setup like this is commonly used to share an Internet connection. One of the LAN machines is connected to the Internet. The rest of the machines access the Internet through that gateway machine. kernel configuration Configuration The following options must be in the kernel configuration file: options IPFIREWALL options IPDIVERT Additionally, at choice, the following may also be suitable: options IPFIREWALL_DEFAULT_TO_ACCEPT options IPFIREWALL_VERBOSE The following must be in /etc/rc.conf: gateway_enable="YES" firewall_enable="YES" firewall_type="OPEN" natd_enable="YES" natd_interface="fxp0" natd_flags="" gateway_enable="YES" Sets up the machine to act as a gateway. Running sysctl net.inet.ip.forwarding=1 would have the same effect. firewall_enable="YES" Enables the firewall rules in /etc/rc.firewall at boot. firewall_type="OPEN" This specifies a predefined firewall ruleset that allows anything in. See /etc/rc.firewall for additional types. natd_interface="fxp0" Indicates which interface to forward packets through (the interface connected to the Internet). natd_flags="" Any additional configuration options passed to &man.natd.8; on boot. Having the previous options defined in /etc/rc.conf would run natd -interface fxp0 at boot. This can also be run manually. It is also possible to use a configuration file for &man.natd.8; when there are too many options to pass. In this case, the configuration file must be defined by adding the following line to /etc/rc.conf: natd_flags="-f /etc/natd.conf" The /etc/natd.conf file will contain a list of configuration options, one per line. For example the next section case would use the following file: redirect_port tcp 192.168.0.2:6667 6667 redirect_port tcp 192.168.0.3:80 80 For more information about the configuration file, consult the &man.natd.8; manual page about the option. Each machine and interface behind the LAN should be assigned IP address numbers in the private network space as defined by RFC 1918 and have a default gateway of the natd machine's internal IP address. For example, client A and B behind the LAN have IP addresses of 192.168.0.2 and 192.168.0.3, while the natd machine's LAN interface has an IP address of 192.168.0.1. Client A and B's default gateway must be set to that of the natd machine, 192.168.0.1. The natd machine's external, or Internet interface does not require any special modification for &man.natd.8; to work. Port Redirection The drawback with &man.natd.8; is that the LAN clients are not accessible from the Internet. Clients on the LAN can make outgoing connections to the world but cannot receive incoming ones. This presents a problem if trying to run Internet services on one of the LAN client machines. A simple way around this is to redirect selected Internet ports on the natd machine to a LAN client. For example, an IRC server runs on client A, and a web server runs on client B. For this to work properly, connections received on ports 6667 (IRC) and 80 (web) must be redirected to the respective machines. The must be passed to &man.natd.8; with the proper options. The syntax is as follows: -redirect_port proto targetIP:targetPORT[-targetPORT] [aliasIP:]aliasPORT[-aliasPORT] [remoteIP[:remotePORT[-remotePORT]]] In the above example, the argument should be: -redirect_port tcp 192.168.0.2:6667 6667 -redirect_port tcp 192.168.0.3:80 80 This will redirect the proper tcp ports to the LAN client machines. The argument can be used to indicate port ranges over individual ports. For example, tcp 192.168.0.2:2000-3000 2000-3000 would redirect all connections received on ports 2000 to 3000 to ports 2000 to 3000 on client A. These options can be used when directly running &man.natd.8;, placed within the natd_flags="" option in /etc/rc.conf, or passed via a configuration file. For further configuration options, consult &man.natd.8; Address Redirection address redirection Address redirection is useful if several IP addresses are available, yet they must be on one machine. With this, &man.natd.8; can assign each LAN client its own external IP address. &man.natd.8; then rewrites outgoing packets from the LAN clients with the proper external IP address and redirects all traffic incoming on that particular IP address back to the specific LAN client. This is also known as static NAT. For example, the IP addresses 128.1.1.1, 128.1.1.2, and 128.1.1.3 belong to the natd gateway machine. 128.1.1.1 can be used as the natd gateway machine's external IP address, while 128.1.1.2 and 128.1.1.3 are forwarded back to LAN clients A and B. The syntax is as follows: -redirect_address localIP publicIP localIP The internal IP address of the LAN client. publicIP The external IP address corresponding to the LAN client. In the example, this argument would read: -redirect_address 192.168.0.2 128.1.1.2 -redirect_address 192.168.0.3 128.1.1.3 Like , these arguments are also placed within the natd_flags="" option of /etc/rc.conf, or passed via a configuration file. With address redirection, there is no need for port redirection since all data received on a particular IP address is redirected. The external IP addresses on the natd machine must be active and aliased to the external interface. Look at &man.rc.conf.5; to do so. Chern Lee Contributed by The <application>inetd</application> <quote>Super-Server</quote> Overview &man.inetd.8; is referred to as the Internet Super-Server because it manages connections for several daemons. Programs that provide network service are commonly known as daemons. inetd serves as a managing server for other daemons. When a connection is received by inetd, it determines which daemon the connection is destined for, spawns the particular daemon and delegates the socket to it. Running one instance of inetd reduces the overall system load as compared to running each daemon individually in stand-alone mode. Primarily, inetd is used to spawn other daemons, but several trivial protocols are handled directly, such as chargen, auth, and daytime. This section will cover the basics in configuring inetd through its command-line options and its configuration file, /etc/inetd.conf. Settings inetd is initialized through the /etc/rc.conf system. The inetd_enable option is set to NO by default, but is often times turned on by sysinstall with the medium security profile. Placing: inetd_enable="YES" or inetd_enable="NO" into /etc/rc.conf can enable or disable inetd starting at boot time. Additionally, different command-line options can be passed to inetd via the inetd_flags option. Command-Line Options inetd synopsis: -d Turn on debugging. -l Turn on logging of successful connections. -w Turn on TCP Wrapping for external services (on by default). -W Turn on TCP Wrapping for internal services which are built into inetd (on by default). -c maximum Specify the default maximum number of simultaneous invocations of each service; the default is unlimited. May be overridden on a per-service basis with the parameter. -C rate Specify the default maximum number of times a service can be invoked from a single IP address in one minute; the default is unlimited. May be overridden on a per-service basis with the parameter. -R rate Specify the maximum number of times a service can be invoked in one minute; the default is 256. A rate of 0 allows an unlimited number of invocations. -a Specify one specific IP address to bind to. Alternatively, a hostname can be specified, in which case the IPv4 or IPv6 address which corresponds to that hostname is used. Usually a hostname is specified when inetd is run inside a &man.jail.8;, in which case the hostname corresponds to the &man.jail.8; environment. When hostname specification is used and both IPv4 and IPv6 bindings are desired, one entry with the appropriate protocol type for each binding is required for each service in /etc/inetd.conf. For example, a TCP-based service would need two entries, one using tcp4 for the protocol and the other using tcp6. -p Specify an alternate file in which to store the process ID. These options can be passed to inetd using the inetd_flags option in /etc/rc.conf. By default, inetd_flags is set to -wW, which turns on TCP wrapping for inetd's internal and external services. For novice users, these parameters usually do not need to be modified or even entered in /etc/rc.conf. An external service is a daemon outside of inetd, which is invoked when a connection is received for it. On the other hand, an internal service is one that inetd has the facility of offering within itself. <filename>inetd.conf</filename> Configuration of inetd is controlled through the /etc/inetd.conf file. When a modification is made to /etc/inetd.conf, inetd can be forced to re-read its configuration file by sending a HangUP signal to the inetd process as shown: Sending <application>inetd</application> a HangUP Signal &prompt.root; kill -HUP `cat /var/run/inetd.pid` Each line of the configuration file specifies an individual daemon. Comments in the file are preceded by a #. The format of /etc/inetd.conf is as follows: service-name socket-type protocol {wait|nowait}[/max-child[/max-connections-per-ip-per-minute]] user[:group][/login-class] server-program server-program-arguments An example entry for the ftpd daemon using IPv4: ftp stream tcp nowait root /usr/libexec/ftpd ftpd -l service-name This is the service name of the particular daemon. It must correspond to a service listed in /etc/services. This determines which port inetd must listen to. If a new service is being created, it must be placed in /etc/services first. socket-type Either stream, dgram, raw, or seqpacket. stream must be used for connection-based, TCP daemons, while dgram is used for daemons utilizing the UDP transport protocol. protocol One of the following: Protocol Explanation tcp, tcp4 TCP IPv4 udp, udp4 UDP IPv4 tcp6 TCP IPv6 udp6 UDP IPv6 tcp46 Both TCP IPv4 and v6 udp46 Both UDP IPv4 and v6 {wait|nowait}[/max-child[/max-connections-per-ip-per-minute]] indicates whether the daemon invoked from inetd is able to handle its own socket or not. socket types must use the option, while stream socket daemons, which are usually multi-threaded, should use . usually hands off multiple sockets to a single daemon, while spawns a child daemon for each new socket. The maximum number of child daemons inetd may spawn can be set using the option. If a limit of ten instances of a particular daemon is needed, a /10 would be placed after . In addition to , another option limiting the maximum connections from a single place to a particular daemon can be enabled. does just this. A value of ten here would limit any particular IP address connecting to a particular service to ten attempts per minute. This is useful to prevent intentional or unintentional resource consumption and Denial of Service (DoS) attacks to a machine. In this field, or is mandatory. and are optional. A stream-type multi-threaded daemon without any or limits would simply be: nowait. The same daemon with a maximum limit of ten daemons would read: nowait/10. Additionally, the same setup with a limit of twenty connections per IP address per minute and a maximum total limit of ten child daemons would read: nowait/10/20. These options are all utilized by the default settings of the fingerd daemon, as seen here: finger stream tcp nowait/3/10 nobody /usr/libexec/fingerd fingerd -s user This is the username that the particular daemon should run as. Most commonly, daemons run as the root user. For security purposes, it is common to find some servers running as the daemon user, or the least privileged nobody user. server-program The full path of the daemon to be executed when a connection is received. If the daemon is a service provided by inetd internally, then should be used. server-program-arguments This works in conjunction with by specifying the arguments, starting with argv[0], passed to the daemon on invocation. If mydaemon -d is the command line, mydaemon -d would be the value of . Again, if the daemon is an internal service, use here. Security Depending on the security profile chosen at install, many of inetd's daemons may be enabled by default. If there is no apparent need for a particular daemon, disable it! Place a # in front of the daemon in question, and send a hangup signal to inetd. Some daemons, such as fingerd, may not be desired at all because they provide an attacker with too much information. Some daemons are not security-conscious and have long, or non-existent timeouts for connection attempts. This allows an attacker to slowly send connections to a particular daemon, thus saturating available resources. It may be a good idea to place and limitations on certain daemons. By default, TCP wrapping is turned on. Consult the &man.hosts.access.5; manual page for more information on placing TCP restrictions on various inetd invoked daemons. Miscellaneous daytime, time, echo, discard, chargen, and auth are all internally provided services of inetd. The auth service provides identity (ident, identd) network services, and is configurable to a certain degree. Consult the &man.inetd.8; manual page for more in-depth information. Parallel Line IP (PLIP) PLIP Parallel Line IP PLIP lets us run TCP/IP between parallel ports. It is useful on machines without network cards, or to install on laptops. In this section, we will discuss: Creating a parallel (laplink) cable. Connecting two computers with PLIP. Creating a Parallel Cable You can purchase a parallel cable at most computer supply stores. If you cannot do that, or you just want to know how it is done, the following table shows how to make one out of a normal parallel printer cable. Wiring a Parallel Cable for Networking A-name A-End B-End Descr. Post/Bit DATA0 -ERROR 2 15 15 2 Data 0/0x01 1/0x08 DATA1 +SLCT 3 13 13 3 Data 0/0x02 1/0x10 DATA2 +PE 4 12 12 4 Data 0/0x04 1/0x20 DATA3 -ACK 5 10 10 5 Strobe 0/0x08 1/0x40 DATA4 BUSY 6 11 11 6 Data 0/0x10 1/0x80 GND 18-25 18-25 GND -
Setting Up PLIP First, you have to get a laplink cable. Then, confirm that both computers have a kernel with &man.lpt.4; driver support: &prompt.root; grep lp /var/run/dmesg.boot lpt0: <Printer> on ppbus0 lpt0: Interrupt-driven port The parallel port must be an interrupt driven port, under &os; 4.X, you should have a line similar to the following in your kernel configuration file: device ppc0 at isa? irq 7 Under &os; 5.X, the /boot/device.hints file should contain the following lines: hint.ppc.0.at="isa" hint.ppc.0.irq="7" Then check if the kernel configuration file has a device plip line or if the plip.ko kernel module is loaded. In both cases the parallel networking interface should appear when you directly use the &man.ifconfig.8; command. Under &os; 4.X like this: &prompt.root; ifconfig lp0 lp0: flags=8810<POINTOPOINT,SIMPLEX,MULTICAST> mtu 1500 and for &os; 5.X: &prompt.root; ifconfig plip0 plip0: flags=8810<POINTOPOINT,SIMPLEX,MULTICAST> mtu 1500 The device name used for parallel interface is different between &os; 4.X (lpX) and &os; 5.X (plipX). Plug in the laplink cable into the parallel interface on both computers. Configure the network interface parameters on both sites as root. For example, if you want connect the host host1 running &os; 4.X with host2 running &os; 5.X: host1 <-----> host2 IP Address 10.0.0.1 10.0.0.2 Configure the interface on host1 by doing: &prompt.root; ifconfig lp0 10.0.0.1 10.0.0.2 Configure the interface on host2 by doing: &prompt.root; ifconfig plip0 10.0.0.2 10.0.0.1 You now should have a working connection. Please read the manual pages &man.lp.4; and &man.lpt.4; for more details. You should also add both hosts to /etc/hosts: 127.0.0.1 localhost.my.domain localhost 10.0.0.1 host1.my.domain host1 10.0.0.2 host2.my.domain To confirm the connection works, go to each host and ping the other. For example, on host1: &prompt.root; ifconfig lp0 lp0: flags=8851<UP,POINTOPOINT,RUNNING,SIMPLEX,MULTICAST> mtu 1500 inet 10.0.0.1 --> 10.0.0.2 netmask 0xff000000 &prompt.root; netstat -r Routing tables Internet: Destination Gateway Flags Refs Use Netif Expire host2 host1 UH 0 0 lp0 &prompt.root; ping -c 4 host2 PING host2 (10.0.0.2): 56 data bytes 64 bytes from 10.0.0.2: icmp_seq=0 ttl=255 time=2.774 ms 64 bytes from 10.0.0.2: icmp_seq=1 ttl=255 time=2.530 ms 64 bytes from 10.0.0.2: icmp_seq=2 ttl=255 time=2.556 ms 64 bytes from 10.0.0.2: icmp_seq=3 ttl=255 time=2.714 ms --- host2 ping statistics --- 4 packets transmitted, 4 packets received, 0% packet loss round-trip min/avg/max/stddev = 2.530/2.643/2.774/0.103 ms Aaron Kaplan Originally Written by Tom Rhodes Restructured and Added by IPv6 IPv6 (also know as IPng IP next generation) is the new version of the well known IP protocol (also know as IPv4). Like the other current *BSD systems, FreeBSD includes the KAME IPv6 reference implementation. So your FreeBSD system comes with all you will need to experiment with IPv6. This section focuses on getting IPv6 configured and running. In the early 1990s, people became aware of the rapidly diminishing address space of IPv4. Given the expansion rate of the Internet there were two major concerns: Running out of addresses. Today this is not so much of a concern anymore since private address spaces (10.0.0.0/8, 192.168.0.0/24, etc.) and Network Address Translation (NAT) are being employed. Router table entries were getting too large. This is still a concern today. IPv6 deals with these and many other issues: 128 bit address space. In other words theoretically there are 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses available. This means there are approximately 6.67 * 10^27 IPv6 addresses per square meter on our planet. Routers will only store network aggregation addresses in their routing tables thus reducing the average space of a routing table to 8192 entries. There are also lots of other useful features of IPv6 such as: Address autoconfiguration (RFC2462) Anycast addresses (one-out-of many) Mandatory multicast addresses IPsec (IP security) Simplified header structure Mobile IP IPv4-to-IPv6 transition mechanisms For more information see: IPv6 overview at playground.sun.com KAME.net 6bone.net Background on IPv6 Addresses There are different types of IPv6 addresses: Unicast, Anycast and Multicast. Unicast addresses are the well known addresses. A packet sent to a unicast address arrives exactly at the interface belonging to the address. Anycast addresses are syntactically indistinguishable from unicast addresses but they address a group of interfaces. The packet destined for an anycast address will arrive at the nearest (in router metric) interface. Anycast addresses may only be used by routers. Multicast addresses identify a group of interfaces. A packet destined for a multicast address will arrive at all interfaces belonging to the multicast group. The IPv4 broadcast address (usually xxx.xxx.xxx.255) is expressed by multicast addresses in IPv6. Reserved IPv6 addresses IPv6 address Prefixlength (Bits) Description Notes :: 128 bits unspecified cf. 0.0.0.0 in IPv4 ::1 128 bits loopback address cf. 127.0.0.1 in IPv4 ::00:xx:xx:xx:xx 96 bits embedded IPv4 The lower 32 bits are the IPv4 address. Also called IPv4 compatible IPv6 address ::ff:xx:xx:xx:xx 96 bits IPv4 mapped IPv6 address The lower 32 bits are the IPv4 address. For hosts which do not support IPv6. fe80:: - feb:: 10 bits link-local cf. loopback address in IPv4 fec0:: - fef:: 10 bits site-local   ff:: 8 bits multicast   001 (base 2) 3 bits global unicast All global unicast addresses are assigned from this pool. The first 3 bits are 001.
Reading IPv6 Addresses The canonical form is represented as: x:x:x:x:x:x:x:x, each x being a 16 Bit hex value. For example FEBC:A574:382B:23C1:AA49:4592:4EFE:9982 Often an address will have long substrings of all zeros therefore each such substring can be abbreviated by ::. For example fe80::1 corresponds to the canonical form fe80:0000:0000:0000:0000:0000:0000:0001. A third form is to write the last 32 Bit part in the well known (decimal) IPv4 style with dots . as separators. For example 2002::10.0.0.1 corresponds to the (hexadecimal) canonical representation 2002:0000:0000:0000:0000:0000:0a00:0001 which in turn is equivalent to writing 2002::a00:1. By now the reader should be able to understand the following: &prompt.root; ifconfig rl0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500 inet 10.0.0.10 netmask 0xffffff00 broadcast 10.0.0.255 inet6 fe80::200:21ff:fe03:8e1%rl0 prefixlen 64 scopeid 0x1 ether 00:00:21:03:08:e1 media: Ethernet autoselect (100baseTX ) status: active fe80::200:21ff:fe03:8e1%rl0 is an auto configured link-local address. It includes the scrambled Ethernet MAC as part of the auto configuration. For further information on the structure of IPv6 addresses see RFC3513. Getting Connected Currently there are four ways to connect to other IPv6 hosts and networks: Join the experimental 6bone Getting an IPv6 network from your upstream provider. Talk to your Internet provider for instructions. Tunnel via 6-to-4 Use the net/freenet6 port if you are on a dial-up connection. Here we will talk on how to connect to the 6bone since it currently seems to be the most popular way. First take a look at the 6bone site and find a 6bone connection nearest to you. Write to the responsible person and with a little bit of luck you will be given instructions on how to set up your connection. Usually this involves setting up a GRE (gif) tunnel. Here is a typical example on setting up a &man.gif.4; tunnel: &prompt.root; ifconfig gif0 create &prompt.root; ifconfig gif0 gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280 &prompt.root; ifconfig gif0 tunnel MY_IPv4_ADDR HIS_IPv4_ADDR &prompt.root; ifconfig gif0 inet6 alias MY_ASSIGNED_IPv6_TUNNEL_ENDPOINT_ADDR Replace the capitalized words by the information you received from the upstream 6bone node. This establishes the tunnel. Check if the tunnel is working by &man.ping6.8; 'ing ff02::1%gif0. You should receive two ping replies. In case you are intrigued by the address ff02:1%gif0, this is a multicast address. %gif0 states that the multicast address at network interface gif0 is to be used. Since we ping a multicast address the other endpoint of the tunnel should reply as well. By now setting up a route to your 6bone uplink should be rather straightforward: &prompt.root; route add -inet6 default -interface gif0 &prompt.root; ping6 -n MY_UPLINK &prompt.root; traceroute6 www.jp.FreeBSD.org (3ffe:505:2008:1:2a0:24ff:fe57:e561) from 3ffe:8060:100::40:2, 30 hops max, 12 byte packets 1 atnet-meta6 14.147 ms 15.499 ms 24.319 ms 2 6bone-gw2-ATNET-NT.ipv6.tilab.com 103.408 ms 95.072 ms * 3 3ffe:1831:0:ffff::4 138.645 ms 134.437 ms 144.257 ms 4 3ffe:1810:0:6:290:27ff:fe79:7677 282.975 ms 278.666 ms 292.811 ms 5 3ffe:1800:0:ff00::4 400.131 ms 396.324 ms 394.769 ms 6 3ffe:1800:0:3:290:27ff:fe14:cdee 394.712 ms 397.19 ms 394.102 ms This output will differ from machine to machine. By now you should be able to reach the IPv6 site www.kame.net and see the dancing tortoise — that is if you have a IPv6 enabled browser such as www/mozilla. DNS in the IPv6 World There are two new types of DNS records for IPv6: AAAA records, A6 records Using AAAA records is straightforward. Assign your hostname to the new IPv6 address you just got by adding: MYHOSTNAME AAAA MYIPv6ADDR To your primary zone DNS file. In case you do not serve your own DNS zones ask your DNS provider. Current versions of bind (version 8.3 and 9) support AAAA records. Harti Brandt Contributed by ATM on &os; 5.X Configuring classical IP over ATM (PVCs) Classical IP over ATM (CLIP) is the simplest method to use ATM with IP. It can be used with switched connections (SVCs) and with permanent connections (PVCs). This section describes how to set up a network based on PVCs. Fully meshed configurations The first method to set up a CLIP with PVCs is to connect each machine to each other machine in the network via a dedicated PVC. While this is simple to configure it tends to become impractical for larger number of machines. The example supposes that we have four machines in the network, each connected to the ATM network with an ATM adapter card. The first step is the planning of the IP addresses and the ATM connections between the machines. We use the following: Host IP Adress hostA 192.168.173.1 hostB 192.168.173.2 hostC 192.168.173.3 hostD 192.168.173.4 To build a fully meshed net we need one ATM connection between each pair of machines: Machines VPI.VCI couple hostA - hostB 0.100 hostA - hostC 0.101 hostA - hostD 0.102 hostB - hostC 0.103 hostB - hostD 0.104 hostC - hostD 0.105 The VPI and VCI values at each end of the connection may of course differ, but for simplicity we assume that they are the same. Next we need to configure the ATM interfaces on each host: hostA&prompt.root; ifconfig hatm0 192.168.173.1 up hostB&prompt.root; ifconfig hatm0 192.168.173.2 up hostC&prompt.root; ifconfig hatm0 192.168.173.3 up hostD&prompt.root; ifconfig hatm0 192.168.173.4 up assuming that the ATM interface is hatm0 on all hosts. Now the PVCs need to configured on hostA (we assume that they are already configured on the ATM switches, you need to consult the manual for the switch on how to do this). hostA&prompt.root; atmconfig natm add 192.168.173.2 hatm0 0 100 llc/snap ubr hostA&prompt.root; atmconfig natm add 192.168.173.3 hatm0 0 101 llc/snap ubr hostA&prompt.root; atmconfig natm add 192.168.173.4 hatm0 0 102 llc/snap ubr hostB&prompt.root; atmconfig natm add 192.168.173.1 hatm0 0 100 llc/snap ubr hostB&prompt.root; atmconfig natm add 192.168.173.3 hatm0 0 103 llc/snap ubr hostB&prompt.root; atmconfig natm add 192.168.173.4 hatm0 0 104 llc/snap ubr hostC&prompt.root; atmconfig natm add 192.168.173.1 hatm0 0 101 llc/snap ubr hostC&prompt.root; atmconfig natm add 192.168.173.2 hatm0 0 103 llc/snap ubr hostC&prompt.root; atmconfig natm add 192.168.173.4 hatm0 0 105 llc/snap ubr hostD&prompt.root; atmconfig natm add 192.168.173.1 hatm0 0 102 llc/snap ubr hostD&prompt.root; atmconfig natm add 192.168.173.2 hatm0 0 104 llc/snap ubr hostD&prompt.root; atmconfig natm add 192.168.173.3 hatm0 0 105 llc/snap ubr Of course other traffic contracts than UBR can be used given the ATM adapter supports those. In this case the name of the traffic contract is followed by the parameters of the traffic. Help for the &man.atmconfig.8; tool can be obtained with: &prompt.root; atmconfig help natm add or in the &man.atmconfig.8; manual page. The same configuration can also be done via /etc/rc.conf. For hostA this would look like: network_interfaces="lo0 hatm0" ifconfig_hatm0="inet 192.168.173.1 up" natm_static_routes="hostB hostC hostD" route_hostB="192.168.173.2 hatm0 0 100 llc/snap ubr" route_hostC="192.168.173.3 hatm0 0 101 llc/snap ubr" route_hostD="192.168.173.4 hatm0 0 102 llc/snap ubr" The current state of all CLIP routes can be obtained with: hostA&prompt.root; atmconfig natm show diff --git a/en_US.ISO8859-1/books/handbook/mail/chapter.sgml b/en_US.ISO8859-1/books/handbook/mail/chapter.sgml index b848ad5896..9d7146b7ab 100644 --- a/en_US.ISO8859-1/books/handbook/mail/chapter.sgml +++ b/en_US.ISO8859-1/books/handbook/mail/chapter.sgml @@ -1,2283 +1,2294 @@ Bill Lloyd Original work by Jim Mock Rewritten by Electronic Mail Synopsis email electronic mail Electronic Mail, better known as email, is one of the most widely used forms of communication today. This chapter provides a basic introduction to running a mail server on &os;, as well as an introduction to sending and receiving email using &os;; however, it is not a complete reference and in fact many important considerations are omitted. For more complete coverage of the subject, the reader is referred to the many excellent books listed in . After reading this chapter, you will know: What software components are involved in sending and receiving electronic mail. Where basic sendmail configuration files are located in FreeBSD. An understanding of the difference between remote and local mailboxes. How to block spammers from illegally using your mail server as a relay. How to install and configure an alternate mail transfer agent on your system, replacing sendmail. How to troubleshoot common mail server problems. How to use SMTP with UUCP. How to set up the system to send mail only. How to use mail with a dialup connection. How to configure SMTP Authentication for added security. How to install and use a Mail User Agent, such as mutt to send and receive email. How to download your mail from a remote POP or IMAP server. How to automatically apply filters and rules to incoming email. Before reading this chapter, you should: Properly set up your network connection (). Properly set up the DNS information for your mail host (). Know how to install additional third-party software (). Using Electronic Mail POP IMAP DNS There are five major parts involved in an email exchange. They are: the user program, the server daemon, DNS, a remote or local mailbox, and of course, the mailhost itself. The User Program This includes command line programs such as mutt, pine, elm, and mail, and GUI programs such as balsa, xfmail to name a few, and something more sophisticated like a WWW browser. These programs simply pass off the email transactions to the local mailhost, either by calling one of the server daemons available, or delivering it over TCP. Mailhost Server Daemon mail server daemons sendmail mail server daemons postfix mail server daemons qmail mail server daemons exim &os; ships with sendmail by default, but also support numerous other mail server daemons, just some of which include: exim; postfix; qmail. The server daemon usually has two functions—it is responsible for receiving incoming mail as well as delivering outgoing mail. It is not responsible for the collection of mail using protocols such as POP or IMAP to read your email, nor does it allow connecting to local mbox or Maildir mailboxes. You may require an additional daemon for that. Older versions of sendmail have some serious security issues which may result in an attacker gaining local and/or remote access to your machine. Make sure that you are running a current version to avoid these problems. Optionally, install an alternative MTA from the &os; Ports Collection. Email and DNS The Domain Name System (DNS) and its daemon named play a large role in the delivery of email. In order to deliver mail from your site to another, the server daemon will look up the remote site in the DNS to determine the host that will receive mail for the destination. This process also occurs when mail is sent from a remote host to your mail server. + + MX record + + DNS is responsible for mapping hostnames to IP addresses, as well as for storing information specific to mail delivery, known as MX records. The MX (Mail eXchanger) record specifies which host, or hosts, will recieve mail for a particular domain. If you do not have an MX record for your hostname or domain, the mail will be delivered directly to your host provided you have an A record pointing your hostname to your IP address. You may view the MX records for any domain by using the &man.host.1; command, as seen in the example below: &prompt.user; host -t mx FreeBSD.org FreeBSD.org mail is handled (pri=10) by mx1.FreeBSD.org Receiving Mail email receiving Receiving mail for your domain is done by the mail host. It will collect all mail sent to your domain and store it either in mbox (the default method for storing mail) or Maildir format, depending on your configuration. Once mail has been stored, it may either be read locally using applications such as &man.mail.1; or mutt, or remotely accessed and collected using protocols such as POP or IMAP. This means that should you only wish to read mail locally, you are not required to install a POP or IMAP server. Accessing remote mailboxes using <acronym>POP</acronym> and <acronym>IMAP</acronym> POP IMAP In order to access mailboxes remotely, you are required to have access to a POP or IMAP server. These protocols allow users to connect to their mailboxes from remote locations with ease. Though both POP and IMAP allow users to remotely access mailboxes, IMAP offers many advantages, some of which are: IMAP can store messages on a remote server as well as fetch them. IMAP supports concurrent updates. IMAP can be extremely useful over low-speed links as it allows users to fetch the structure of messages without downloading them; it can also perform tasks such as searching on the server in order to minimize data transfer between clients and servers. In order to install a POP or IMAP server, the following steps should be performed: Choose an IMAP or POP server that best suits your needs. The following POP and IMAP servers are well known and serve as some good examples: qpopper; teapop; imap-uw; courier-imap; Install the POP or IMAP daemon of your choosing from the ports collection. Where required, modify /etc/inetd.conf to load the POP or IMAP server. It should be noted that both POP and IMAP transmit information, including username and password credentials in clear-text. This means that if you wish to secure the transmission of information across these protocols, you should consider tunneling sessions over &man.ssh.1;. Tunneling sessions is described in . Accessing local mailboxes Mailboxes may be accessed locally by directly utilizing MUA's on the server on which the mailbox resides. This can be done using applications such as mutt or &man.mail.1;. The Mail Host mail host The mail host is the name given to a server that is responsible for delivering and receiving mail for your host, and possibly your network. Christopher Shumway Contributed by <application>sendmail</application> Configuration sendmail &man.sendmail.8; is the default Mail Transfer Agent (MTA) in FreeBSD. sendmail's job is to accept mail from Mail User Agents (MUA) and deliver it to the appropriate mailer as defined by its configuration file. sendmail can also accept network connections and deliver mail to local mailboxes or deliver it to another program. sendmail uses the following configuration files: /etc/mail/access /etc/mail/aliases /etc/mail/local-host-names /etc/mail/mailer.conf /etc/mail/mailertable /etc/mail/sendmail.cf /etc/mail/virtusertable Filename Function /etc/mail/access sendmail access database file /etc/mail/aliases Mailbox aliases /etc/mail/local-host-names Lists of hosts sendmail accepts mail for /etc/mail/mailer.conf Mailer program configuration /etc/mail/mailertable Mailer delivery table /etc/mail/sendmail.cf sendmail master configuration file /etc/mail/virtusertable Virtual users and domain tables <filename>/etc/mail/access</filename> The access database defines what host(s) or IP addresses have access to the local mail server and what kind of access they have. Hosts can be listed as , , or simply passed to sendmail's error handling routine with a given mailer error. Hosts that are listed as , which is the default, are allowed to send mail to this host as long as the mail's final destination is the local machine. Hosts that are listed as are rejected for all mail connections. Hosts that have the option for their hostname are allowed to send mail for any destination through this mail server. Configuring the <application>sendmail</application> Access Database cyberspammer.com 550 We don't accept mail from spammers FREE.STEALTH.MAILER@ 550 We don't accept mail from spammers another.source.of.spam REJECT okay.cyberspammer.com OK 128.32 RELAY In this example we have five entries. Mail senders that match the left hand side of the table are affected by the action on the right side of the table. The first two examples give an error code to sendmail's error handling routine. The message is printed to the remote host when a mail matches the left hand side of the table. The next entry rejects mail from a specific host on the Internet, another.source.of.spam. The next entry accepts mail connections from a host okay.cyberspammer.com, which is more exact than the cyberspammer.com line above. More specific matches override less exact matches. The last entry allows relaying of electronic mail from hosts with an IP address that begins with 128.32. These hosts would be able to send mail through this mail server that are destined for other mail servers. When this file is updated, you need to run make in /etc/mail/ to update the database. <filename>/etc/mail/aliases</filename> The aliases database contains a list of virtual mailboxes that are expanded to other user(s), files, programs or other aliases. Here are a few examples that can be used in /etc/mail/aliases: Mail Aliases root: localuser ftp-bugs: joe,eric,paul bit.bucket: /dev/null procmail: "|/usr/local/bin/procmail" The file format is simple; the mailbox name on the left side of the colon is expanded to the target(s) on the right. The first example simply expands the mailbox root to the mailbox localuser, which is then looked up again in the aliases database. If no match is found, then the message is delivered to the local user localuser. The next example shows a mail list. Mail to the mailbox ftp-bugs is expanded to the three local mailboxes joe, eric, and paul. Note that a remote mailbox could be specified as user@example.com. The next example shows writing mail to a file, in this case /dev/null. The last example shows sending mail to a program, in this case the mail message is written to the standard input of /usr/local/bin/procmail through a &unix; pipe. When this file is updated, you need to run make in /etc/mail/ to update the database. <filename>/etc/mail/local-host-names</filename> This is a list of hostnames &man.sendmail.8; is to accept as the local host name. Place any domains or hosts that sendmail is to be receiving mail for. For example, if this mail server was to accept mail for the domain example.com and the host mail.example.com, its local-host-names might look something like this: example.com mail.example.com When this file is updated, &man.sendmail.8; needs to be restarted to read the changes. <filename>/etc/mail/sendmail.cf</filename> sendmail's master configuration file, sendmail.cf controls the overall behavior of sendmail, including everything from rewriting e-mail addresses to printing rejection messages to remote mail servers. Naturally, with such a diverse role, this configuration file is quite complex and its details are a bit out of the scope of this section. Fortunately, this file rarely needs to be changed for standard mail servers. The master sendmail configuration file can be built from &man.m4.1; macros that define the features and behavior of sendmail. Please see /usr/src/contrib/sendmail/cf/README for some of the details. When changes to this file are made, sendmail needs to be restarted for the changes to take effect. <filename>/etc/mail/virtusertable</filename> The virtusertable maps mail addresses for virtual domains and mailboxes to real mailboxes. These mailboxes can be local, remote, aliases defined in /etc/mail/aliases or files. Example Virtual Domain Mail Map root@example.com root postmaster@example.com postmaster@noc.example.net @example.com joe In the above example, we have a mapping for a domain example.com. This file is processed in a first match order down the file. The first item maps root@example.com to the local mailbox root. The next entry maps postmaster@example.com to the mailbox postmaster on the host noc.example.net. Finally, if nothing from example.com has matched so far, it will match the last mapping, which matches every other mail message addressed to someone at example.com. This will be mapped to the local mailbox joe. Andrew Boothman Written by Gregory Neil Shapiro Information taken from e-mails written by Changing Your Mail Transfer Agent email change mta As already mentioned, FreeBSD comes with sendmail already installed as your MTA (Mail Transfer Agent). Therefore by default it is in charge of your outgoing and incoming mail. However, for a variety of reasons, some system administrators want to change their system's MTA. These reasons range from simply wanting to try out another MTA to needing a specific feature or package which relies on another mailer. Fortunately, whatever the reason, FreeBSD makes it easy to make the change. Install a New MTA You have a wide choice of MTAs available. A good starting point is the FreeBSD Ports Collection where you will be able to find many. Of course you are free to use any MTA you want from any location, as long as you can make it run under FreeBSD. Start by installing your new MTA. Once it is installed it gives you a chance to decide if it really fulfills your needs, and also gives you the opportunity to configure your new software before getting it to take over from sendmail. When doing this, you should be sure that installing the new software will not attempt to overwrite system binaries such as /usr/bin/sendmail. Otherwise, your new mail software has essentially been put into service before you have configured it. Please refer to your chosen MTA's documentation for information on how to configure the software you have chosen. Disable <application>sendmail</application> The procedure used to start sendmail changed significantly between 4.5-RELEASE and 4.6-RELEASE. Therefore, the procedure used to disable it is subtly different. FreeBSD 4.5-STABLE before 2002/4/4 and Earlier (Including 4.5-RELEASE and Earlier) Enter: sendmail_enable="NO" into /etc/rc.conf. This will disable sendmail's incoming mail service, but if /etc/mail/mailer.conf (see below) is not changed, sendmail will still be used to send e-mail. FreeBSD 4.5-STABLE after 2002/4/4 (Including 4.6-RELEASE and Later) In order to completely disable sendmail you must use sendmail_enable="NONE" in /etc/rc.conf. If you disable sendmail's outgoing mail service in this way, it is important that you replace it with a fully working alternative mail delivery system. If you choose not to, system functions such as &man.periodic.8; will be unable to deliver their results by e-mail as they would normally expect to. Many parts of your system may expect to have a functional sendmail-compatible system. If applications continue to use sendmail's binaries to try to send e-mail after you have disabled them, mail could go into an inactive sendmail queue, and never be delivered. If you only want to disable sendmail's incoming mail service, you should set sendmail_enable="NO" in /etc/rc.conf. More information on sendmail's startup options is available from the &man.rc.sendmail.8; manual page. Running Your New MTA on Boot You may have a choice of two methods for running your new MTA on boot, again depending on what version of FreeBSD you are running. FreeBSD 4.5-STABLE before 2002/4/11 (Including 4.5-RELEASE and Earlier) Add a script to /usr/local/etc/rc.d/ that ends in .sh and is executable by root. The script should accept start and stop parameters. At startup time the system scripts will execute the command /usr/local/etc/rc.d/supermailer.sh start which you can also use to manually start the server. At shutdown time, the system scripts will use the stop option, running the command /usr/local/etc/rc.d/supermailer.sh stop which you can also use to manually stop the server while the system is running. FreeBSD 4.5-STABLE after 2002/4/11 (Including 4.6-RELEASE and Later) With later versions of FreeBSD, you can use the above method or you can set mta_start_script="filename" in /etc/rc.conf, where filename is the name of some script that you want executed at boot to start your MTA. Replacing <application>sendmail</application> as the System's Default Mailer The program sendmail is so ubiquitous as standard software on &unix; systems that some software just assumes it is already installed and configured. For this reason, many alternative MTA's provide their own compatible implementations of the sendmail command-line interface; this facilitates using them as drop-in replacements for sendmail. Therefore, if you are using an alternative mailer, you will need to make sure that software trying to execute standard sendmail binaries such as /usr/bin/sendmail actually executes your chosen mailer instead. Fortunately, FreeBSD provides a system called &man.mailwrapper.8; that does this job for you. When sendmail is operating as installed, you will find something like the following in /etc/mail/mailer.conf: sendmail /usr/libexec/sendmail/sendmail send-mail /usr/libexec/sendmail/sendmail mailq /usr/libexec/sendmail/sendmail newaliases /usr/libexec/sendmail/sendmail hoststat /usr/libexec/sendmail/sendmail purgestat /usr/libexec/sendmail/sendmail This means that when any of these common commands (such as sendmail itself) are run, the system actually invokes a copy of mailwrapper named sendmail, which checks mailer.conf and executes /usr/libexec/sendmail/sendmail instead. This system makes it easy to change what binaries are actually executed when these default sendmail functions are invoked. Therefore if you wanted /usr/local/supermailer/bin/sendmail-compat to be run instead of sendmail, you could change /etc/mail/mailer.conf to read: sendmail /usr/local/supermailer/bin/sendmail-compat send-mail /usr/local/supermailer/bin/sendmail-compat mailq /usr/local/supermailer/bin/mailq-compat newaliases /usr/local/supermailer/bin/newaliases-compat hoststat /usr/local/supermailer/bin/hoststat-compat purgestat /usr/local/supermailer/bin/purgestat-compat Finishing Once you have everything configured the way you want it, you should either kill the sendmail processes that you no longer need and start the processes belonging to your new software, or simply reboot. Rebooting will also give you the opportunity to ensure that you have correctly configured your system to start your new MTA automatically on boot. Troubleshooting email troubleshooting Why do I have to use the FQDN for hosts on my site? You will probably find that the host is actually in a different domain; for example, if you are in foo.bar.edu and you wish to reach a host called mumble in the bar.edu domain, you will have to refer to it by the fully-qualified domain name, mumble.bar.edu, instead of just mumble. BIND Traditionally, this was allowed by BSD BIND resolvers. However the current version of BIND that ships with FreeBSD no longer provides default abbreviations for non-fully qualified domain names other than the domain you are in. So an unqualified host mumble must either be found as mumble.foo.bar.edu, or it will be searched for in the root domain. This is different from the previous behavior, where the search continued across mumble.bar.edu, and mumble.edu. Have a look at RFC 1535 for why this was considered bad practice, or even a security hole. As a good workaround, you can place the line: search foo.bar.edu bar.edu instead of the previous: domain foo.bar.edu into your /etc/resolv.conf. However, make sure that the search order does not go beyond the boundary between local and public administration, as RFC 1535 calls it. + + MX record + + sendmail says mail loops back to myself This is answered in the sendmail FAQ as follows: I'm getting these error messages: 553 MX list for domain.net points back to relay.domain.net 554 <user@domain.net>... Local configuration error How can I solve this problem? You have asked mail to the domain (e.g., domain.net) to be forwarded to a specific host (in this case, relay.domain.net) by using an MX record, but the relay machine does not recognize itself as domain.net. Add domain.net to /etc/mail/local-host-names [known as /etc/sendmail.cw prior to version 8.10] (if you are using FEATURE(use_cw_file)) or add Cw domain.net to /etc/mail/sendmail.cf. The sendmail FAQ can be found at and is recommended reading if you want to do any tweaking of your mail setup. PPP How can I run a mail server on a dial-up PPP host? You want to connect a FreeBSD box on a LAN to the Internet. The FreeBSD box will be a mail gateway for the LAN. The PPP connection is non-dedicated. UUCP + + MX record + There are at least two ways to do this. One way is to use UUCP. Another way is to get a full-time Internet server to provide secondary MX services for your domain. For example, if your company's domain is example.com and your Internet service provider has set example.net up to provide secondary MX services to your domain: example.com. MX 10 example.com. MX 20 example.net. Only one host should be specified as the final recipient (add Cw example.com in /etc/mail/sendmail.cf on example.com). When the sending sendmail is trying to deliver the mail it will try to connect to you (example.com) over the modem link. It will most likely time out because you are not online. The program sendmail will automatically deliver it to the secondary MX site, i.e. your Internet provider (example.net). The secondary MX site will then periodically try to connect to your host and deliver the mail to the primary MX host (example.com). You might want to use something like this as a login script: #!/bin/sh # Put me in /usr/local/bin/pppmyisp ( sleep 60 ; /usr/sbin/sendmail -q ) & /usr/sbin/ppp -direct pppmyisp If you are going to create a separate login script for a user you could use sendmail -qRexample.com instead in the script above. This will force all mail in your queue for example.com to be processed immediately. A further refinement of the situation is as follows: Message stolen from the &a.isp;. > we provide the secondary MX for a customer. The customer connects to > our services several times a day automatically to get the mails to > his primary MX (We do not call his site when a mail for his domains > arrived). Our sendmail sends the mailqueue every 30 minutes. At the > moment he has to stay 30 minutes online to be sure that all mail is > gone to the primary MX. > > Is there a command that would initiate sendmail to send all the mails > now? The user has not root-privileges on our machine of course. In the privacy flags section of sendmail.cf, there is a definition Opgoaway,restrictqrun Remove restrictqrun to allow non-root users to start the queue processing. You might also like to rearrange the MXs. We are the 1st MX for our customers like this, and we have defined: # If we are the best MX for a host, try directly instead of generating # local config error. OwTrue That way a remote site will deliver straight to you, without trying the customer connection. You then send to your customer. Only works for hosts, so you need to get your customer to name their mail machine customer.com as well as hostname.customer.com in the DNS. Just put an A record in the DNS for customer.com. Why do I keep getting Relaying Denied errors when sending mail from other hosts? In default FreeBSD installations, sendmail is configured to only send mail from the host it is running on. For example, if a POP server is available, then users will be able to check mail from school, work, or other remote locations but they still will not be able to send outgoing emails from outside locations. Typically, a few moments after the attempt, an email will be sent from MAILER-DAEMON with a 5.7 Relaying Denied error message. There are several ways to get around this. The most straightforward solution is to put your ISP's address in a relay-domains file at /etc/mail/relay-domains. A quick way to do this would be: &prompt.root; echo "your.isp.example.com" > /etc/mail/relay-domains After creating or editing this file you must restart sendmail. This works great if you are a server administrator and do not wish to send mail locally, or would like to use a point and click client/system on another machine or even another ISP. It is also very useful if you only have one or two email accounts set up. If there is a large number of addresses to add, you can simply open this file in your favorite text editor and then add the domains, one per line: your.isp.example.com other.isp.example.net users-isp.example.org www.example.org Now any mail sent through your system, by any host in this list (provided the user has an account on your system), will succeed. This is a very nice way to allow users to send mail from your system remotely without allowing people to send SPAM through your system. Advanced Topics The following section covers more involved topics such as mail configuration and setting up mail for your entire domain. Basic Configuration email configuration Out of the box, you should be able to send email to external hosts as long as you have set up /etc/resolv.conf or are running your own name server. If you would like to have mail for your host delivered to the MTA (e.g., sendmail) on your own FreeBSD host, there are two methods: Run your own name server and have your own domain. For example, FreeBSD.org Get mail delivered directly to your host. This is done by delivering mail directly to the current DNS name for your machine. For example, example.FreeBSD.org. SMTP Regardless of which of the above you choose, in order to have mail delivered directly to your host, it must have a permanent static IP address (not a dynamic address, as with most PPP dial-up configurations). If you are behind a firewall, it must pass SMTP traffic on to you. If you want to receive mail directly at your host, you need to be sure of either of two things: MX record Make sure that the (lowest-numbered) MX record in your DNS points to your host's IP address. Make sure there is no MX entry in your DNS for your host. Either of the above will allow you to receive mail directly at your host. Try this: &prompt.root; hostname example.FreeBSD.org &prompt.root; host example.FreeBSD.org example.FreeBSD.org has address 204.216.27.XX If that is what you see, mail directly to yourlogin@example.FreeBSD.org should work without problems (assuming sendmail is running correctly on example.FreeBSD.org). If instead you see something like this: &prompt.root; host example.FreeBSD.org example.FreeBSD.org has address 204.216.27.XX example.FreeBSD.org mail is handled (pri=10) by hub.FreeBSD.org All mail sent to your host (example.FreeBSD.org) will end up being collected on hub under the same username instead of being sent directly to your host. The above information is handled by your DNS server. The DNS record that carries mail routing information is the Mail eXchange entry. If no MX record exists, mail will be delivered directly to the host by way of its IP address. The MX entry for freefall.FreeBSD.org at one time looked like this: freefall MX 30 mail.crl.net freefall MX 40 agora.rdrop.com freefall MX 10 freefall.FreeBSD.org freefall MX 20 who.cdrom.com As you can see, freefall had many MX entries. The lowest MX number is the host that receives mail directly if available; if it is not accessible for some reason, the others (sometimes called backup MXes) accept messages temporarily, and pass it along when a lower-numbered host becomes available, eventually to the lowest-numbered host. Alternate MX sites should have separate Internet connections from your own in order to be most useful. Your ISP or another friendly site should have no problem providing this service for you. Mail for Your Domain In order to set up a mailhost (a.k.a. mail server) you need to have any mail sent to various workstations directed to it. Basically, you want to claim any mail for any hostname in your domain (in this case *.FreeBSD.org) and divert it to your mail server so your users can receive their mail on the master mail server. DNS To make life easiest, a user account with the same username should exist on both machines. Use &man.adduser.8; to do this. The mailhost you will be using must be the designated mail exchanger for each workstation on the network. This is done in your DNS configuration like so: example.FreeBSD.org A 204.216.27.XX ; Workstation MX 10 hub.FreeBSD.org ; Mailhost This will redirect mail for the workstation to the mailhost no matter where the A record points. The mail is sent to the MX host. You cannot do this yourself unless you are running a DNS server. If you are not, or cannot run your own DNS server, talk to your ISP or whoever provides your DNS. If you are doing virtual email hosting, the following information will come in handy. For this example, we will assume you have a customer with his own domain, in this case customer1.org, and you want all the mail for customer1.org sent to your mailhost, mail.myhost.com. The entry in your DNS should look like this: customer1.org MX 10 mail.myhost.com You do not need an A record for customer1.org if you only want to handle email for that domain. Be aware that pinging customer1.org will not work unless an A record exists for it. The last thing that you must do is tell sendmail on your mailhost what domains and/or hostnames it should be accepting mail for. There are a few different ways this can be done. Either of the following will work: Add the hosts to your /etc/mail/local-host-names file if you are using the FEATURE(use_cw_file). If you are using a version of sendmail earlier than 8.10, the file is /etc/sendmail.cw. Add a Cwyour.host.com line to your /etc/sendmail.cf or /etc/mail/sendmail.cf if you are using sendmail 8.10 or higher. SMTP with UUCP The sendmail configuration that ships with FreeBSD is designed for sites that connect directly to the Internet. Sites that wish to exchange their mail via UUCP must install another sendmail configuration file. Tweaking /etc/mail/sendmail.cf manually is an advanced topic. sendmail version 8 generates config files via &man.m4.1; preprocessing, where the actual configuration occurs on a higher abstraction level. The &man.m4.1; configuration files can be found under /usr/src/usr.sbin/sendmail/cf. If you did not install your system with full sources, the sendmail configuration set has been broken out into a separate source distribution tarball. Assuming you have your FreeBSD source code CDROM mounted, do: &prompt.root; cd /cdrom/src &prompt.root; cat scontrib.?? | tar xzf - -C /usr/src/contrib/sendmail This extracts to only a few hundred kilobytes. The file README in the cf directory can serve as a basic introduction to &man.m4.1; configuration. The best way to support UUCP delivery is to use the mailertable feature. This creates a database that sendmail can use to make routing decisions. First, you have to create your .mc file. The directory /usr/src/usr.sbin/sendmail/cf/cf contains a few examples. Assuming you have named your file foo.mc, all you need to do in order to convert it into a valid sendmail.cf is: &prompt.root; cd /usr/src/usr.sbin/sendmail/cf/cf &prompt.root; make foo.cf &prompt.root; cp foo.cf /etc/mail/sendmail.cf A typical .mc file might look like: VERSIONID(`Your version number') OSTYPE(bsd4.4) FEATURE(accept_unresolvable_domains) FEATURE(nocanonify) FEATURE(mailertable, `hash -o /etc/mail/mailertable') define(`UUCP_RELAY', your.uucp.relay) define(`UUCP_MAX_SIZE', 200000) define(`confDONT_PROBE_INTERFACES') MAILER(local) MAILER(smtp) MAILER(uucp) Cw your.alias.host.name Cw youruucpnodename.UUCP The lines containing accept_unresolvable_domains, nocanonify, and confDONT_PROBE_INTERFACES features will prevent any usage of the DNS during mail delivery. The UUCP_RELAY clause is needed to support UUCP delivery. Simply put an Internet hostname there that is able to handle .UUCP pseudo-domain addresses; most likely, you will enter the mail relay of your ISP there. Once you have this, you need an /etc/mail/mailertable file. If you have only one link to the outside that is used for all your mails, the following file will suffice: # # makemap hash /etc/mail/mailertable.db < /etc/mail/mailertable . uucp-dom:your.uucp.relay A more complex example might look like this: # # makemap hash /etc/mail/mailertable.db < /etc/mail/mailertable # horus.interface-business.de uucp-dom:horus .interface-business.de uucp-dom:if-bus interface-business.de uucp-dom:if-bus .heep.sax.de smtp8:%1 horus.UUCP uucp-dom:horus if-bus.UUCP uucp-dom:if-bus . uucp-dom: The first three lines handle special cases where domain-addressed mail should not be sent out to the default route, but instead to some UUCP neighbor in order to shortcut the delivery path. The next line handles mail to the local Ethernet domain that can be delivered using SMTP. Finally, the UUCP neighbors are mentioned in the .UUCP pseudo-domain notation, to allow for a uucp-neighbor !recipient override of the default rules. The last line is always a single dot, matching everything else, with UUCP delivery to a UUCP neighbor that serves as your universal mail gateway to the world. All of the node names behind the uucp-dom: keyword must be valid UUCP neighbors, as you can verify using the command uuname. As a reminder that this file needs to be converted into a DBM database file before use. The command line to accomplish this is best placed as a comment at the top of the mailertable file. You always have to execute this command each time you change your mailertable file. Final hint: if you are uncertain whether some particular mail routing would work, remember the option to sendmail. It starts sendmail in address test mode; simply enter 3,0, followed by the address you wish to test for the mail routing. The last line tells you the used internal mail agent, the destination host this agent will be called with, and the (possibly translated) address. Leave this mode by typing CtrlD. &prompt.user; sendmail -bt ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address> > 3,0 foo@example.com canonify input: foo @ example . com ... parse returns: $# uucp-dom $@ your.uucp.relay $: foo < @ example . com . > > ^D Bill Moran Contributed by Setting up to send only There are many instances where you may only want to send mail through a relay. Some examples are: Your computer is a desktop machine, but you want to use programs such as &man.send-pr.1;. To do so, you should use your ISP's mail relay. The computer is a server that does not handle mail locally, but needs to pass off all mail to a relay for processing. Just about any MTA is capable of filling this particular niche. Unfortunately, it can be very difficult to properly configure a full-featured MTA just to handle offloading mail. Programs such as sendmail and postfix are largely overkill for this use. Additionally, if you are using a typical Internet access service, your agreement may forbid you from running a mail server. The easiest way to fulfill those needs is to install the mail/ssmtp port. Execute the following commands as root: &prompt.root; cd /usr/ports/mail/ssmtp &prompt.root; make install replace clean Once installed, mail/ssmtp can be configured with a four-line file located at /usr/local/etc/ssmtp/ssmtp.conf: root=yourrealemail@example.com mailhub=mail.example.com rewriteDomain=example.com hostname=_HOSTNAME_ Make sure you use your real email address for root. Enter your ISP's outgoing mail relay in place of mail.example.com (some ISPs call this the outgoing mail server or SMTP server). Make sure you disable sendmail by setting sendmail_enable="NONE" in /etc/rc.conf. mail/ssmtp has some other options available. See the example configuration file in /usr/local/etc/ssmtp or the manual page of ssmtp for some examples and more information. Setting up ssmtp in this manner will allow any software on your computer that needs to send mail to function properly, while not violating your ISP's usage policy or allowing your computer to be hijacked for spamming. Using Mail with a Dialup Connection If you have a static IP address, you should not need to adjust anything from the defaults. Set your host name to your assigned Internet name and sendmail will do the rest. If you have a dynamically assigned IP number and use a dialup PPP connection to the Internet, you will probably have a mailbox on your ISPs mail server. Let's assume your ISP's domain is example.net, and that your user name is user, you have called your machine bsd.home, and your ISP has told you that you may use relay.example.net as a mail relay. In order to retrieve mail from your mailbox, you must install a retrieval agent. The fetchmail utility is a good choice as it supports many different protocols. This program is available as a package or from the ports collection (mail/fetchmail). Usually, your ISP will provide POP. If you are using user PPP, you can automatically fetch your mail when an Internet connection is established with the following entry in /etc/ppp/ppp.linkup: MYADDR: !bg su user -c fetchmail If you are using sendmail (as shown below) to deliver mail to non-local accounts, you probably want to have sendmail process your mailqueue as soon as your Internet connection is established. To do this, put this command after the fetchmail command in /etc/ppp/ppp.linkup: !bg su user -c "sendmail -q" Assume that you have an account for user on bsd.home. In the home directory of user on bsd.home, create a .fetchmailrc file: poll example.net protocol pop3 fetchall pass MySecret This file should not be readable by anyone except user as it contains the password MySecret. In order to send mail with the correct from: header, you must tell sendmail to use user@example.net rather than user@bsd.home. You may also wish to tell sendmail to send all mail via relay.example.net, allowing quicker mail transmission. The following .mc file should suffice: VERSIONID(`bsd.home.mc version 1.0') OSTYPE(bsd4.4)dnl FEATURE(nouucp)dnl MAILER(local)dnl MAILER(smtp)dnl Cwlocalhost Cwbsd.home MASQUERADE_AS(`example.net')dnl FEATURE(allmasquerade)dnl FEATURE(masquerade_envelope)dnl FEATURE(nocanonify)dnl FEATURE(nodns)dnl define(`SMART_HOST', `relay.example.net') Dmbsd.home define(`confDOMAIN_NAME',`bsd.home')dnl define(`confDELIVERY_MODE',`deferred')dnl Refer to the previous section for details of how to turn this .mc file into a sendmail.cf file. Also, do not forget to restart sendmail after updating sendmail.cf. James Gorham Written by SMTP Authentication Having SMTP Authentication in place on your mail server has a number of benefits. SMTP Authentication can add another layer of security to sendmail, and has the benefit of giving mobile users who switch hosts the ability to use the same mail server without the need to reconfigure their mail client settings each time. Install security/cyrus-sasl from the ports. You can find this port in security/cyrus-sasl. security/cyrus-sasl has a number of compile time options to choose from and, for the method we will be using here, make sure to select the option. After installing security/cyrus-sasl, edit /usr/local/lib/sasl/Sendmail.conf (or create it if it does not exist) and add the following line: pwcheck_method: passwd This method will enable sendmail to authenticate against your FreeBSD passwd database. This saves the trouble of creating a new set of usernames and passwords for each user that needs to use SMTP authentication, and keeps the login and mail password the same. Now edit /etc/make.conf and add the following lines: SENDMAIL_CFLAGS=-I/usr/local/include/sasl1 -DSASL SENDMAIL_LDFLAGS=-L/usr/local/lib SENDMAIL_LDADD=-lsasl These lines will give sendmail the proper configuration options for linking to cyrus-sasl at compile time. Make sure that cyrus-sasl has been installed before recompiling sendmail. Recompile sendmail by executing the following commands: &prompt.root; cd /usr/src/usr.sbin/sendmail &prompt.root; make cleandir &prompt.root; make obj &prompt.root; make &prompt.root; make install The compile of sendmail should not have any problems if /usr/src has not been changed extensively and the shared libraries it needs are available. After sendmail has been compiled and reinstalled, edit your /etc/mail/freebsd.mc file (or whichever file you use as your .mc file. Many administrators choose to use the output from &man.hostname.1; as the .mc file for uniqueness). Add these lines to it: dnl set SASL options TRUST_AUTH_MECH(`GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN')dnl define(`confAUTH_MECHANISMS', `GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN')dnl define(`confDEF_AUTH_INFO', `/etc/mail/auth-info')dnl These options configure the different methods available to sendmail for authenticating users. If you would like to use a method other than pwcheck, please see the included documentation. Finally, run &man.make.1; while in /etc/mail. That will run your new .mc file and create a .cf file named freebsd.cf (or whatever name you have used for your .mc file). Then use the command make install restart, which will copy the file to sendmail.cf, and will properly restart sendmail. For more information about this process, you should refer to /etc/mail/Makefile. If all has gone correctly, you should be able to enter your login information into the mail client and send a test message. For further investigation, set the of sendmail to 13 and watch /var/log/maillog for any errors. You may wish to add the following lines to /etc/rc.conf so this service will be available after every system boot: sasl_pwcheck_enable="YES" sasl_pwcheck_program="/usr/local/sbin/pwcheck" This will ensure the initialization of SMTP_AUTH upon system boot. For more information, please see the sendmail page regarding SMTP authentication. Marc Silver Contributed by Mail User Agents Mail User Agents A Mail User Agent (MUA) is an application that is used to send and receive email. Furthermore, as email evolves and becomes more complex, MUA's are becoming increasingly powerful in the way they interact with email; this gives users increased functionality and flexibility. &os; contains support for numerous mail user agents, all of which can be easily installed using the FreeBSD Ports Collection. Users may choose between graphical email clients such as evolution or balsa; console based clients such as mutt, pine or mail; or the web interfaces used by some large organizations. mail &man.mail.1; is the default Mail User Agent (MUA) in &os;. It's a console based MUA that offers all the basic functionality required to send and receive text-based email, though it is limited in interaction abilities with attachments and can only support local mailboxes. Although mail does not natively support interaction with POP or IMAP servers, these mailboxes may be downloaded to a local mbox file using an application such as fetchmail, which will be discussed later in this chapter. In order to send and receive email, simply invoke the mail command as per the following example: &prompt.user; mail The contents of the user mailbox in /var/mail/ are automatically read by the mail utility. Should the mailbox be empty, the utility exits with a message indicating that no mails could be found. Once the mailbox has been read, the application interface is started, and a list of messages will be displayed. Messages are automatically numbered, as can be seen in the following example: Mail version 8.1 6/6/93. Type ? for help. "/var/mail/marcs": 3 messages 3 new >N 1 root@localhost Mon Mar 8 14:05 14/510 "test" N 2 root@localhost Mon Mar 8 14:05 14/509 "user account" N 3 root@localhost Mon Mar 8 14:05 14/509 "sample" Messages can now be read by using the t mail command, suffixed by the message number that should be displayed. In this example, we will read the first email: & t 1 Message 1: From root@localhost Mon Mar 8 14:05:52 2004 X-Original-To: marcs@localhost Delivered-To: marcs@localhost To: marcs@localhost Subject: test Date: Mon, 8 Mar 2004 14:05:52 +0200 (SAST) From: root@localhost (Charlie Root) This is a test message, please reply if you receive it. As can be seen in the example above, the t key will cause the message to be displayed with full headers. To display the list of messages again, the h key should be used. If the email requires a response, you may use mail to reply, by using either the R or r mail keys. The R key instructs mail to reply only to the sender of the email, while r replies not only to the sender, but also to other recipients of the message. You may also suffix these commands with the mail number which you would like make a reply to. Once this has been done, the response should be entered, and the end of the message should be marked by a single . on a new line. An example can be seen below: & R 1 To: root@localhost Subject: Re: test Thank you, I did get your email. . EOT In order to send new email, the m key should be used, followed by the recipient email address. Multiple recipients may also be specified by separating each address with the , delimiter. The subject of the message may then be entered, followed by the message contents. The end of the message should be specified by putting a single . on a new line. & mail root@localhost Subject: I mastered mail Now I can send and receive email using mail ... :) . EOT While inside the mail utility, the ? command may be used to display help at any time. The &man.mail.1; manual page should also be consulted for more help with mail. As previously mentioned, the &man.mail.1; command was not originally designed to handle attachments, and thus deals with them very poorly. Newer MUA's such as mutt handle attachments in a much more intelligent way. But should you still wish to use the mail command, the converters/mpack port may be of considerable use. mutt mutt is a small yet very powerful Mail User Agent, with excellent features, just some of which include: The ability to thread messages; PGP support for digital signing and encryption of email; MIME Support; Maildir Support; Highly customizable. All of these features help to make mutt one of the most advanced mail user agents available. See for more information on mutt. The stable version of mutt may be installed using the mail/mutt port, while the current development version may be installed via the mail/mutt-devel port. After the port has been installed, mutt can be started by issuing the following command: &prompt.user; mutt mutt will automatically read the contents of the user mailbox in /var/mail and display the contents if applicable. If no mails are found in the user mailbox, then mutt will wait for commands from the user. The example below shows mutt displaying a list of messages. In order to read an email, simply select it using the cursor keys, and press the Enter key. An example of mutt displaying email can be seen below: As with the &man.mail.1; command, mutt allows users to reply only to the sender of the message as well as to all recipients. To reply only to the sender of the email, use the r keyboard shortcut. To send a group reply, which will be sent to the original sender as well as all the message recipients, use the g shortcut. mutt makes use of the &man.vi.1; command as an editor for creating and replying to emails. This may be customized by the user by creating or editing their own .muttrc and setting the variable. In order to compose a new mail message, press m. After a valid subject has been given, mutt will start &man.vi.1; and the mail can be written. Once the contents of the mail are complete, save and quit from vi and mutt will resume, displaying a summary screen of the mail that is to be delivered. In order to send the mail, press y. An example of the summary screen can be seen below: mutt also contains extensive help, which can be accessed from most of the menus by pressing the ? key. The top line also displays the keyboard shortcuts where appropriate. pine pine is aimed at a beginner user, but also includes some advanced features. The pine software has had several remote vulnerabilities discovered in the past, which allowed remote attackers to execute arbitrary code as users on the local system, by the action of sending a specially-prepared email. All such known problems have been fixed, but the pine code is written in a very insecure style and the &os; Security Officer believes there are likely to be other undiscovered vulnerabilities. You install pine at your own risk. The current version of pine may be installed using the mail/pine4 port. Once the port has installed, pine can be started by issuing the following command: &prompt.user; pine The first time that pine is run it displays a greeting page with a brief introduction, as well as a request from the pine development team to send an anonymous email message allowing them to judge how many users are using their client. To send this anonymous message, press Enter, or alternatively press E to exit the greeting without sending an anonymous message. An example of the greeting page can be seen below: Users are then presented with the main menu, which can be easily navigated using the cursor keys. This main menu provides shortcuts for the composing new mails, browsing of mail directories, and even the administration of address book entries. Below the main menu, relevant keyboard shortcuts to perform functions specific to the task at hand are shown. The default directory opened by pine is the inbox. To view the message index, press I, or select the MESSAGE INDEX option as seen below: The message index shows messages in the current directory, and can be navigated by using the cursor keys. Highlighted messages can be read by pressing the Enter key. In the screenshot below, a sample message is displayed by pine. Keyboard shortcuts are displayed as a reference at the bottom of the screen. An example of one of these shortcuts is the r key, which tells the MUA to reply to the current message being displayed. Replying to an email in pine is done using the pico editor, which is installed by default with pine. The pico utility makes it easy to navigate around the message and is slightly more forgiving on novice users than &man.vi.1; or &man.mail.1;. Once the reply is complete, the message can be sent by pressing CtrlX . The pine application will ask for confirmation. The pine application can be customized using the option from the main menu. Consult for more information. Marc Silver Contributed by Using fetchmail Using fetchmail fetchmail is a full-featured IMAP and POP client which allows users to automatically download mail from remote IMAP and POP servers and save it into local mailboxes; there it can be accessed more easily. fetchmail can be installed using the mail/fetchmail port, and offers various features, some of which include: Support of POP3, APOP, KPOP, IMAP, ETRN and ODMR protocols. Ability to forward mail using SMTP, which allows filtering, forwarding, and aliasing to function normally. May be run in daemon mode to check periodically for new messages. Can retrieve multiple mailboxes and forward them based on configuration, to different local users. While it is outside the scope of this document to explain all of fetchmail's features, some basic features will be explained. The fetchmail utility requires a configuration file known as .fetchmailrc, in order to run correctly. This file includes server information as well as login credentials. Due to the sensitive nature of the contents of this file, it is advisable to make it readable only by the owner, with the following command: &prompt.user; chmod 600 .fetchmailrc The following .fetchmailrc serves as an example for downloading a single user mailbox using POP. It tells fetchmail to connect to example.com using a username of joesoap and a password of XXX. This example assumes that the user joesoap is also a user on the local system. poll example.com protocol pop3 username "joesoap" password "XXX" The next example connects to multiple POP and IMAP servers and redirects to different local usernames where applicable: poll example.com proto pop3: user "joesoap", with password "XXX", is "jsoap" here; user "andrea", with password "XXXX"; poll example2.net proto imap: user "john", with password "XXXXX", is "myth" here; The fetchmail utility can be run in daemon mode by running it with the flag, followed by the interval (in seconds) that fetchmail should poll servers listed in the .fetchmailrc file. The following example would cause fetchmail to poll every 60 seconds: &prompt.user; fetchmail -d 60 More information on fetchmail can be found at . Marc Silver Contributed by Using procmail Using procmail The procmail utility is an incredibly powerful application used to filter incoming mail. It allows users to define rules which can be matched to incoming mails to perform specific functions or to reroute mail to alternative mailboxes and/or email addresses. procmail can be installed using the mail/procmail port. Once installed, it can be directly integrated into most MTAs; consult your MTA documentation for more information. Alternatively, procmail can be integrated by adding the following line to a .forward in the home directory of the user utilizing procmail features: "|exec /usr/local/bin/procmail || exit 75" The following section will display some basic procmail rules, as well as brief descriptions on what they do. These rules, and others must be inserted into a .procmailrc file, which must reside in a user's the home directory. The majority of these rules can also be found in the &man.procmailex.5; manual page. Forward all mail from user@example.com to an external address of goodmail@example2.com: :0 * ^From.*user@example.com ! goodmail@example2.com Forward all mails shorter than 1000 bytes to an external address of goodmail@example2.com: :0 * < 1000 ! goodmail@example2.com Send all mail sent to alternate@example.com into a mailbox called alternate: :0 * ^TOalternate@example.com alternate Send all mail with a subject of Spam to /dev/null: :0 ^Subject:.*Spam /dev/null A useful recipe that parses incoming &os;.org mailing lists and places each list in its own mailbox: :0 * ^Sender:.owner-freebsd-\/[^@]+@FreeBSD.ORG { LISTNAME=${MATCH} :0 * LISTNAME??^\/[^@]+ FreeBSD-${MATCH} }