diff --git a/en_US.ISO8859-1/books/handbook/basics/chapter.xml b/en_US.ISO8859-1/books/handbook/basics/chapter.xml index 70c03885cb..096b812ebf 100644 --- a/en_US.ISO8859-1/books/handbook/basics/chapter.xml +++ b/en_US.ISO8859-1/books/handbook/basics/chapter.xml @@ -1,2855 +1,2675 @@ Chris Shumway Rewritten by UNIX Basics Synopsis - The following chapter will cover the basic commands and - functionality of the FreeBSD operating system. Much of this - material is relevant for any &unix;-like operating system. Feel - free to skim over this chapter if you are familiar with the - material. If you are new to FreeBSD, then you will definitely - want to read through this chapter carefully. + This chapter covers the basic commands and functionality of + the &os; operating system. Much of this material is relevant + for any &unix;-like operating system. New &os; users are + encouraged to read through this chapter carefully. After reading this chapter, you will know: How to use the virtual consoles of - FreeBSD. + &os;. - How &unix; file permissions work along with - understanding file flags in &os;. + How &unix; file permissions and &os; file flags + work. The default &os; file system layout. The &os; disk organization. How to mount and unmount file systems. What processes, daemons, and signals are. What a shell is, and how to change your default login environment. How to use basic text editors. What devices and device nodes are. What binary format is used under &os;. How to read manual pages for more information. Virtual Consoles and Terminals virtual consoles terminals - FreeBSD can be used in various ways. One of them is typing + &os; can be used in various ways. One of them is typing commands to a text terminal. A lot of the flexibility and power of a &unix; operating system is readily available at your hands - when using FreeBSD this way. This section describes what + when using &os; this way. This section describes what terminals and consoles are, and - how you can use them in FreeBSD. + how you can use them in &os;. The Console console - If you have not configured FreeBSD to automatically start - a graphical environment during startup, the system will - present you with a login prompt after it boots, right after - the startup scripts finish running. You will see something - similar to: - - Additional ABI support:. -Local package initialization:. -Additional TCP options:. - -Fri Sep 20 13:01:06 EEST 2002 + Unless &os; has been configured to automatically start + a graphical environment during startup, the system will boot + into a command line login prompt, as seen in this + example: -FreeBSD/i386 (pc3.example.org) (ttyv0) + FreeBSD/amd64 (pc3.example.org) (ttyv0) login: - The messages might be a bit different on your system, but - you will see something similar. The last two lines are what - we are interested in right now. The second last line - reads: - - FreeBSD/i386 (pc3.example.org) (ttyv0) - - This line contains some bits of information about the - system you have just booted. You are looking at a - FreeBSD console, running on an Intel or - compatible processor of the x86 architecture - This is what i386 means. Note that - even if you are not running FreeBSD on an Intel 386 CPU, - this is going to be i386. It is not - the type of your processor, but the processor - architecture that is shown here. - . The name of this machine (every &unix; machine - has a name) is pc3.example.org, and you are - now looking at its system console—the - ttyv0 terminal. - - Finally, the last line is always: - - login: - - This is the part where you are supposed to type in your - username to log into FreeBSD. The next section - describes how you can do this. + The first line contains some information about the + system. The amd64 indicates that the + system in this example is running a 64-bit version of &os;. + The hostname is pc3.example.org, and + ttyv0 indicates that this is the + system console. + + The second line is the login prompt. The next section + describes how to log into &os; at this prompt. - Logging into FreeBSD + Logging into &os; - FreeBSD is a multiuser, multiprocessing system. This is + &os; is a multiuser, multiprocessing system. This is the formal description that is usually given to a system that can be used by many different people, who simultaneously run a lot of programs on a single machine. Every multiuser system needs some way to distinguish one - user from the rest. In FreeBSD (and all the + user from the rest. In &os; (and all the &unix;-like operating systems), this is accomplished by requiring that every user must log into the system before being able to run programs. Every user has a unique name (the username) and a personal, - secret key (the password). FreeBSD will ask + secret key (the password). &os; will ask for these two before allowing a user to run any programs. startup scripts - Right after FreeBSD boots and finishes running its startup - scripts - Startup scripts are programs that are run - automatically by FreeBSD when booting. Their main - function is to set things up for everything else to run, - and start any services that you have configured to run in - the background doing useful things. - , it will present you with a prompt and ask for a - valid username: + When a &os; system boots, startup scripts are + automatically executed in order to prepare the system and to + start any services which have been configured to start at + system boot. Once the system finishes running its startup + scripts, it will present a login prompt: login: - For the sake of this example, let us assume that your - username is john. Type - john at this prompt and press - Enter. You should then be presented with a - prompt to enter a password: - - login: john -Password: - - Type in john's password now, and - press Enter. The password is - not echoed! You need not worry about this - right now. Suffice it to say that it is done for security + Type the username that was configured during system installation and + press Enter. Then enter the password + associated with the username and press Enter. + The password is not echoed for security reasons. - If you have typed your password correctly, you should by - now be logged into FreeBSD and ready to try out all the + Once the correct password is input, the message of + the day (MOTD) will be displayed followed + by a command prompt (a #, + $, or % character). You + are now logged into the &os; console and ready to try the available commands. - - You should see the MOTD or message of - the day followed by a command prompt (a #, - $, or % character). - This indicates you have successfully logged into - FreeBSD. - Multiple Consoles - - Running &unix; commands in one console is fine, but - FreeBSD can run many programs at once. Having one console - where commands can be typed would be a bit of a waste when an - operating system like FreeBSD can run dozens of programs at - the same time. This is where virtual consoles - can be very helpful. - - FreeBSD can be configured to present you with many - different virtual consoles. You can switch from one of them - to any other virtual console by pressing a couple of keys on - your keyboard. Each console has its own different output - channel, and FreeBSD takes care of properly redirecting - keyboard input and monitor output as you switch from one - virtual console to the next. - - Special key combinations have been reserved by FreeBSD for - switching consoles - A fairly technical and accurate description of all the - details of the FreeBSD console and keyboard drivers can be - found in the manual pages of &man.syscons.4;, - &man.atkbd.4;, &man.vidcontrol.1; and &man.kbdcontrol.1;. - We will not expand on the details here, but the interested - reader can always consult the manual pages for a more - detailed and thorough explanation of how things - work. - . You can use + Virtual Consoles + + &os; can be configured to provide many virtual consoles + for inputting commands. Each virtual console has its own + login prompt and output channel, and &os; takes care of + properly redirecting keyboard input and monitor output as you + switch between virtual consoles. + + Special key combinations have been reserved by &os; for + switching consoles. + Refer to &man.syscons.4;, &man.atkbd.4;, + &man.vidcontrol.1; and &man.kbdcontrol.1; for a more + technical description of the &os; console and its keyboard + drivers.. Use AltF1, AltF2, through AltF8 - to switch to a different virtual console in FreeBSD. - - As you are switching from one console to the next, FreeBSD - takes care of saving and restoring the screen output. The - result is an illusion of having multiple - virtual screens and keyboards that you can use - to type commands for FreeBSD to run. The programs that you - launch on one virtual console do not stop running when that - console is not visible. They continue running when you have - switched to a different virtual console. + to switch to a different virtual console in &os;. + + When switching from one console to the next, &os; takes + care of saving and restoring the screen output. The result is + an illusion of having multiple + virtual screens and keyboards that can be used + to type commands for &os; to run. The programs that are + launched in one virtual console do not stop running when that + console is not visible because the user has switched to a + different virtual console. The <filename>/etc/ttys</filename> File - The default configuration of FreeBSD will start up with - eight virtual consoles. This is not a hardwired setting - though, and you can easily customize your installation to boot - with more or fewer virtual consoles. The number and settings - of the virtual consoles are configured in the - /etc/ttys file. - - You can use the /etc/ttys file to - configure the virtual consoles of FreeBSD. Each uncommented - line in this file (lines that do not start with a - # character) contains settings for a single - terminal or virtual console. The default version of this file - that ships with FreeBSD configures nine virtual consoles, and - enables eight of them. They are the lines that start with - ttyv: - - # name getty type status comments + By default, &os; is configured to start eight virtual + consoles. The configuration can be customized to start + more or fewer virtual consoles. To change the number of and + the settings of the virtual consoles, edit + /etc/ttys. + + Each uncommented line in /etc/ttys + (lines that do not start with a # + character) contains settings for a single terminal or virtual + console. The default version configures nine virtual + consoles, and enables eight of them. They are the lines that + start with ttyv: + + # name getty type status comments # ttyv0 "/usr/libexec/getty Pc" cons25 on secure # Virtual terminals ttyv1 "/usr/libexec/getty Pc" cons25 on secure ttyv2 "/usr/libexec/getty Pc" cons25 on secure ttyv3 "/usr/libexec/getty Pc" cons25 on secure ttyv4 "/usr/libexec/getty Pc" cons25 on secure ttyv5 "/usr/libexec/getty Pc" cons25 on secure ttyv6 "/usr/libexec/getty Pc" cons25 on secure ttyv7 "/usr/libexec/getty Pc" cons25 on secure ttyv8 "/usr/X11R6/bin/xdm -nodaemon" xterm off secure For a detailed description of every column in this file - and all the options you can use to set things up for the - virtual consoles, consult the &man.ttys.5; manual page. + and the available options for the virtual consoles, refer to + &man.ttys.5;. Single User Mode Console - A detailed description of what - single user mode is can be found in - . It is worth noting that - there is only one console when you are running FreeBSD in - single user mode. There are no virtual consoles available. - The settings of the single user mode console can also be found - in the /etc/ttys file. Look for the line - that starts with console: + A detailed description of single user mode + can be found here. + There is only one console when &os; is in single user mode as + no other virtual consoles are available in this mode. The + settings for single user mode are found in this section of + /etc/ttys: - # name getty type status comments + # name getty type status comments # # If console is marked "insecure", then init will ask for the root password # when going to single-user mode. -console none unknown off secure +console none unknown off secure As the comments above the console - line indicate, you can edit this line and change - secure to insecure. - If you do that, when FreeBSD boots into single user mode, it - will still ask for the root - password. + line indicate, editing secure to + insecure will prompt for the + root password when booting into single + user mode. The default setting enters single user mode + without prompting for a password. - Be careful when changing this to + Be careful when changing this setting to insecure. If you ever forget the root password, booting into - single user mode is a bit involved. It is still possible, - but it might be a bit hard for someone who is not very - comfortable with the FreeBSD booting process and the - programs involved. + single user mode is still possible, but may be difficult for + someone who is not comfortable with the &os; booting + process. Changing Console Video Modes - The FreeBSD console default video mode may be adjusted to - 1024x768, 1280x1024, or any other size supported by your + The &os; console default video mode may be adjusted to + 1024x768, 1280x1024, or any other size supported by the graphics chip and monitor. To use a different video mode load the VESA module: &prompt.root; kldload vesa - Then determine what video modes are supported - by your hardware by using &man.vidcontrol.1;. To - get a list of supported video modes issue the - following: + To determine which video modes are supported by the + hardware, use &man.vidcontrol.1;. To get a list of supported + video modes issue the following: &prompt.root; vidcontrol -i mode - The output of this command is a list of video modes that - are supported by your hardware. You can then choose to use a - new video mode by passing it to &man.vidcontrol.1; in a - root console: + The output of this command lists the video modes that + are supported by the hardware. To select a new video mode, + specify the mode using &man.vidcontrol.1; as the + root user: &prompt.root; vidcontrol MODE_279 If the new video mode is acceptable, it can be permanently - set on boot by setting it in the - /etc/rc.conf file: + set on boot by adding it to + /etc/rc.conf: allscreens_flags="MODE_279" Permissions UNIX - FreeBSD, being a direct descendant of BSD &unix;, is based + &os;, being a direct descendant of BSD &unix;, is based on several key &unix; concepts. The first and most pronounced - is that FreeBSD is a multi-user operating system. The system - can handle several users all working simultaneously on - completely unrelated tasks. The system is responsible for - properly sharing and managing requests for hardware devices, - peripherals, memory, and CPU time fairly to each user. + is that &os; is a multi-user operating system that can handle + several users working simultaneously on completely unrelated + tasks. The system is responsible for properly sharing and + managing requests for hardware devices, peripherals, memory, and + CPU time fairly to each user. Because the system is capable of supporting multiple users, everything the system manages has a set of permissions governing who can read, write, and execute the resource. These permissions are stored as three octets broken into three pieces, one for the owner of the file, one for the group that the file belongs to, and one for everyone else. This numerical representation works like this: permissions file permissions Value Permission Directory Listing 0 No read, no write, no execute --- 1 No read, no write, execute --x 2 No read, write, no execute -w- 3 No read, write, execute -wx 4 Read, no write, no execute r-- 5 Read, no write, execute r-x 6 Read, write, no execute rw- 7 Read, write, execute rwx ls directories - You can use the command line - argument to &man.ls.1; to view a long directory listing that - includes a column with information about a file's permissions - for the owner, group, and everyone else. For example, a - ls -l in an arbitrary directory may - show: + Use the argument to &man.ls.1; to view a + long directory listing that includes a column of information + about a file's permissions for the owner, group, and everyone + else. For example, a ls -l in an arbitrary + directory may show: &prompt.user; ls -l total 530 -rw-r--r-- 1 root wheel 512 Sep 5 12:31 myfile -rw-r--r-- 1 root wheel 512 Sep 5 12:31 otherfile --rw-r--r-- 1 root wheel 7680 Sep 5 12:31 email.txt -... - - Here is how the first column of ls -l is - broken up: - - -rw-r--r-- - - The first (leftmost) character tells if this file is a - regular file, a directory, a special character device, a socket, - or any other special pseudo-file device. In this case, the - - indicates a regular file. The next three - characters, rw- in this example, give the - permissions for the owner of the file. The next three - characters, r--, give the permissions for the - group that the file belongs to. The final three characters, - r--, give the permissions for the rest of the - world. A dash means that the permission is turned off. In the - case of this file, the permissions are set so the owner can read - and write to the file, the group can read the file, and the rest - of the world can only read the file. According to the table - above, the permissions for this file would be - 644, where each digit represents the three - parts of the file's permission. - - This is all well and good, but how does the system control - permissions on devices? FreeBSD actually treats most hardware - devices as a file that programs can open, read, and write data - to just like any other file. These special device files are - stored on the /dev directory. +-rw-r--r-- 1 root wheel 7680 Sep 5 12:31 email.txt + + The first (leftmost) character in the first column indicates + whether this file is a regular file, a directory, a special + character device, a socket, or any other special pseudo-file + device. In this example, the - indicates a + regular file. The next three characters, rw- + in this example, give the permissions for the owner of the file. + The next three characters, r--, give the + permissions for the group that the file belongs to. The final + three characters, r--, give the permissions + for the rest of the world. A dash means that the permission is + turned off. In this example, the permissions are set so the + owner can read and write to the file, the group can read the + file, and the rest of the world can only read the file. + According to the table above, the permissions for this file + would be 644, where each digit represents the + three parts of the file's permission. + + How does the system control permissions on devices? &os; + treats most hardware devices as a file that programs can open, + read, and write data to. These special device files are + stored in /dev/. Directories are also treated as files. They have read, write, and execute permissions. The executable bit for a directory has a slightly different meaning than that of files. - When a directory is marked executable, it means it can be - traversed into, that is, it is possible to cd - (change directory) into it. This also means that within the - directory it is possible to access files whose names are known - (subject, of course, to the permissions on the files - themselves). - - In particular, in order to perform a directory listing, read - permission must be set on the directory, whilst to delete a file - that one knows the name of, it is necessary to have write + When a directory is marked executable, it means it is possible + to change into that directory using + cd. This also means that it is + possible to access the files within that directory, subject to + the permissions on the files themselves. + + In order to perform a directory listing, the read permission + must be set on the directory. In order to delete a file that + one knows the name of, it is necessary to have write and execute permissions to the directory containing the file. There are more permission bits, but they are primarily used in special circumstances such as setuid binaries and sticky - directories. If you want more information on file permissions - and how to set them, be sure to look at the &man.chmod.1; manual - page. + directories. For more information on file permissions and how + to set them, refer to &man.chmod.1;. Tom Rhodes Contributed by Symbolic Permissions permissions symbolic - Symbolic permissions, sometimes referred to as symbolic - expressions, use characters in place of octal values to assign - permissions to files or directories. Symbolic expressions use - the syntax of (who) (action) (permissions), where the - following values are available: + Symbolic permissions use characters instead of octal + values to assign permissions to files or directories. + Symbolic permissions use the syntax of (who) (action) + (permissions), where the following values are + available: Option Letter Represents (who) u User (who) g Group owner (who) o Other (who) a All (world) (action) + Adding permissions (action) - Removing permissions (action) = Explicitly set permissions (permissions) r Read (permissions) w Write (permissions) x Execute (permissions) t Sticky bit (permissions) s Set UID or GID - These values are used with the &man.chmod.1; command - just like before, but with letters. For an example, you could - use the following command to block other users from accessing + These values are used with &man.chmod.1;, but with + letters instead of numbers. For example, the following + command would block other users from accessing FILE: &prompt.user; chmod go= FILE A comma separated list can be provided when more than one - set of changes to a file must be made. For example the - following command will remove the group and + set of changes to a file must be made. For example, the + following command removes the group and world write permission on - FILE, then it adds the execute + FILE, and adds the execute permissions for everyone: &prompt.user; chmod go-w,a+x FILE Tom Rhodes Contributed by &os; File Flags - In addition to file permissions discussed previously, &os; - supports the use of file flags. These flags add - an additional level of security and control over files, but - not directories. - - These file flags add an additional level of control over - files, helping to ensure that in some cases not even the - root can remove or alter files. + In addition to file permissions, &os; supports the use of + file flags. These flags add an additional + level of security and control over files, but not + directories. With file flags, even + root can be prevented from removing or + altering files. - File flags are altered by using the &man.chflags.1; - utility, using a simple interface. For example, to enable the - system undeletable flag on the file + File flags are modified using &man.chflags.1;. For + example, to enable the system undeletable flag on the file file1, issue the following command: &prompt.root; chflags sunlink file1 - And to disable the system undeletable flag, - issue the previous command with no in - front of the . Observe: + To disable the system undeletable flag, put a + no in front of the + : &prompt.root; chflags nosunlink file1 - To view the flags of this file, use the &man.ls.1; command - with the flags: + To view the flags of a file, use with + &man.ls.1;: &prompt.root; ls -lo file1 - The output should look like the following: - -rw-r--r-- 1 trhodes trhodes sunlnk 0 Mar 1 05:54 file1 - Several flags may only added or removed to files by the + Several file flags may only added or removed by the root user. In other cases, the file - owner may set these flags. It is recommended that - administrators read over the &man.chflags.1; and - &man.chflags.2; manual pages for more information. + owner may set its file flags. Refer to &man.chflags.1; and + &man.chflags.2; for more information. Tom Rhodes Contributed by The <literal>setuid</literal>, <literal>setgid</literal>, and <literal>sticky</literal> Permissions Other than the permissions already discussed, there are three other specific settings that all administrators should know about. They are the setuid, - setgid and sticky + setgid, and sticky permissions. These settings are important for some &unix; operations as they provide functionality not normally granted to normal users. To understand them, the difference between the real - user ID and effective user ID must also be noted. + user ID and effective user ID must be noted. The real user ID is the UID who owns or starts the process. The effective UID - is the user ID the process runs as. As an example, the - &man.passwd.1; utility runs with the real user ID as the - user changing their password; however, to manipulate the - password database, it runs as the effective ID of the - root user. This is what allows normal - users to change their passwords without seeing a + is the user ID the process runs as. As an example, + &man.passwd.1; runs with the real user ID when a user changes + their password. However, in order to update the password + database, the command runs as the effective ID of the + root user. This allows users to change + their passwords without seeing a Permission Denied error. - - The nosuid &man.mount.8; option will - cause these binaries to silently fail. That is, they will - fail to execute without ever alerting the user. That option - is also not completely reliable as a - nosuid wrapper may be able to circumvent - it; according to the &man.mount.8; manual page. - - The setuid permission may be set by prefixing a permission set with the number four (4) as shown in the following example: &prompt.root; chmod 4755 suidexample.sh - The permissions on the + The permissions on suidexample.sh - file should now look like the following: + now look like the following: -rwsr-xr-x 1 trhodes trhodes 63 Aug 29 06:36 suidexample.sh - It should be noticeable from this example that an - s is now part of the permission set - designated for the file owner, replacing the executable - bit. This allows utilities which need elevated permissions, - such as passwd. + Note that a s is now part of the + permission set designated for the file owner, replacing the + executable bit. This allows utilities which need elevated + permissions, such as passwd. + + + The nosuid &man.mount.8; option will + cause such binaries to silently fail without alerting + the user. That option is not completely reliable as a + nosuid wrapper may be able to circumvent + it. + To view this in real time, open two terminals. On one, start the passwd process as a normal user. While it waits for a new password, check the process - table and look at the user information of the - passwd command. + table and look at the user information for + passwd: In terminal A: Changing local password for trhodes Old Password: In terminal B: &prompt.root; ps aux | grep passwd trhodes 5232 0.0 0.2 3420 1608 0 R+ 2:10AM 0:00.00 grep passwd root 5211 0.0 0.2 3620 1724 2 I+ 2:09AM 0:00.01 passwd As stated above, the passwd is run by a normal user, but is using the effective UID of root. The setgid permission performs the same function as the setuid permission; except that it alters the group settings. When an application - or utility is ran with this setting, it will be granted the - permissions based on the group that owns the file, not - the user who started the process. + or utility executes with this setting, it will be granted the + permissions based on the group that owns the file, not the + user who started the process. To set the setgid permission on a - file, provide the chmod command with a - leading two (2) as in the following example: + file, provide chmod with a leading two + (2): &prompt.root; chmod 2755 sgidexample.sh - The new setting may be viewed as before, notice the + In the following listing, notice that the s is now in the field designated for the group permission settings: -rwxr-sr-x 1 trhodes trhodes 44 Aug 31 01:49 sgidexample.sh In these examples, even though the shell script in question is an executable file, it will not run with a different EUID or effective user ID. This is because shell scripts may not access the &man.setuid.2; system calls. - The first two special permission bits we discussed - (the setuid and setgid - permission bits) may lower system security, by allowing for - elevated permissions. There is a third special permission bit - that can strengthen the security of a system: the - sticky bit. - - The sticky bit, when set on a - directory, allows file deletion only by the file owner. This - permission set is useful to prevent file deletion in public - directories, such as - /tmp, by users who do - not own the file. To utilize this permission, prefix the - permission with a one (1). For example: + The setuid and + setgid permission bits may lower system + security, by allowing for elevated permissions. The third + special permission, the sticky bit, can + strengthen the security of a system. + + When the sticky bit is set on a + directory, it allows file deletion only by the file owner. + This is useful to prevent file deletion in public directories, + such as /tmp, by users + who do not own the file. To utilize this permission, prefix + the permission set with a one (1): &prompt.root; chmod 1777 /tmp - Now, it is possible to see the effect by using the - ls command: + The sticky bit permission will display + as a t at the very end of the permission + set: &prompt.root; ls -al / | grep tmp drwxrwxrwt 10 root wheel 512 Aug 31 01:49 tmp - The sticky bit permission is - distinguishable from the t at the very - end of the set. Directory Structure directory hierarchy - The FreeBSD directory hierarchy is fundamental to obtaining + The &os; directory hierarchy is fundamental to obtaining an overall understanding of the system. The most important - concept to grasp is that of the root directory, - /. This directory is the first one mounted at - boot time and it contains the base system necessary to prepare - the operating system for multi-user operation. The root - directory also contains mount points for other file systems that - are mounted during the transition to multi-user - operation. + directory is root or, /. This directory is the + first one mounted at boot time and it contains the base system + necessary to prepare the operating system for multi-user + operation. The root directory also contains mount points for + other file systems that are mounted during the transition to + multi-user operation. A mount point is a directory where additional file systems can be grafted onto a parent file system (usually the root file - system). This is further described in - . Standard mount points - include /usr, /var, - /tmp, /mnt, and - /cdrom. These directories are usually - referenced to entries in the file - /etc/fstab. - /etc/fstab is a table of various file - systems and mount points for reference by the system. Most of - the file systems in /etc/fstab are mounted - automatically at boot time from the script &man.rc.8; unless - they contain the option. Details can be - found in . + system). This is further described in . Standard mount points + include /usr/, + /var/, + /tmp/, + /mnt/, and + /cdrom/. These + directories are usually referenced to entries in + /etc/fstab. This file is a table of + various file systems and mount points and is read by the system. + Most of the file systems in /etc/fstab are + mounted automatically at boot time from the script &man.rc.8; + unless their entry includes . Details + can be found in . A complete description of the file system hierarchy is - available in &man.hier.7;. For now, a brief overview of the - most common directories will suffice. + available in &man.hier.7;. The following table provides a brief + overview of the most common directories. Directory Description / Root directory of the file system. /bin/ User utilities fundamental to both single-user and multi-user environments. /boot/ Programs and configuration files used during operating system bootstrap. /boot/defaults/ - Default bootstrapping configuration files; see - &man.loader.conf.5;. + Default boot configuration files. Refer to + &man.loader.conf.5; for details. /dev/ - Device nodes; see &man.intro.4;. + Device nodes. Refer to &man.intro.4; for + details. /etc/ System configuration files and scripts. /etc/defaults/ - Default system configuration files; see - &man.rc.8;. + Default system configuration files. Refer to + &man.rc.8; for details. /etc/mail/ Configuration files for mail transport agents such as &man.sendmail.8;. /etc/namedb/ - named configuration files; see - &man.named.8;. + named configuration files. + Refer to &man.named.8; for details. /etc/periodic/ - Scripts that are run daily, weekly, and monthly, - via &man.cron.8;; see &man.periodic.8;. + Scripts that run daily, weekly, and monthly, + via &man.cron.8;. Refer to &man.periodic.8; for + details. /etc/ppp/ - ppp configuration files; see - &man.ppp.8;. + ppp configuration files as + described in &man.ppp.8;. /mnt/ Empty directory commonly used by system administrators as a temporary mount point. /proc/ - Process file system; see &man.procfs.5;, - &man.mount.procfs.8;. + Process file system. Refer to &man.procfs.5;, + &man.mount.procfs.8; for details. /rescue/ Statically linked programs for emergency - recovery; see &man.rescue.8;. + recovery as described in &man.rescue.8;. /root/ Home directory for the root account. /sbin/ System programs and administration utilities fundamental to both single-user and multi-user environments. /tmp/ - Temporary files. The contents of - /tmp are - usually NOT preserved across a system reboot. A - memory-based file system is often mounted at - /tmp. This can - be automated using the tmpmfs-related variables of - &man.rc.conf.5; (or with an entry in - /etc/fstab; see - &man.mdmfs.8;). + Temporary files which are usually + not preserved across a system + reboot. A memory-based file system is often mounted + at /tmp. This + can be automated using the tmpmfs-related variables of + &man.rc.conf.5; or with an entry in + /etc/fstab; refer to + &man.mdmfs.8; for details. /usr/ The majority of user utilities and applications. /usr/bin/ Common utilities, programming tools, and applications. /usr/include/ Standard C include files. /usr/lib/ Archive libraries. /usr/libdata/ Miscellaneous utility data files. /usr/libexec/ - System daemons & system utilities (executed - by other programs). + System daemons and system utilities executed + by other programs. /usr/local/ - Local executables, libraries, etc. Also used as - the default destination for the FreeBSD ports + Local executables and libraries. Also used as + the default destination for the &os; ports framework. Within /usr/local, the general layout sketched out by &man.hier.7; for /usr should be used. Exceptions are the man directory, which is directly under /usr/local rather than under /usr/local/share, and the ports documentation is in share/doc/port. /usr/obj/ Architecture-specific target tree produced by building the /usr/src tree. /usr/ports/ - The FreeBSD Ports Collection (optional). + The &os; Ports Collection (optional). /usr/sbin/ - System daemons & system utilities (executed - by users). + System daemons and system utilities executed + by users. /usr/share/ Architecture-independent files. /usr/src/ BSD and/or local source files. - - /usr/X11R6/ - X11R6 distribution executables, libraries, etc - (optional). - - /var/ Multi-purpose log, temporary, transient, and spool files. A memory-based file system is sometimes - mounted at - /var. This can - be automated using the varmfs-related variables of - &man.rc.conf.5; (or with an entry in - /etc/fstab; see - &man.mdmfs.8;). + mounted at /var. This can be + automated using the varmfs-related variables in + &man.rc.conf.5; or with an entry in + /etc/fstab; refer to + &man.mdmfs.8; for details. /var/log/ Miscellaneous system log files. /var/mail/ User mailbox files. /var/spool/ Miscellaneous printer and mail system spooling directories. /var/tmp/ - Temporary files. The files are usually preserved + Temporary files which are usually preserved across a system reboot, unless /var is a memory-based file system. /var/yp/ NIS maps. Disk Organization - The smallest unit of organization that FreeBSD uses to find + The smallest unit of organization that &os; uses to find files is the filename. Filenames are case-sensitive, which means that readme.txt and - README.TXT are two separate files. FreeBSD - does not use the extension (.txt) of a file - to determine whether the file is a program, or a document, or - some other form of data. + README.TXT are two separate files. &os; + does not use the extension of a file to determine whether the + file is a program, document, or some other form of data. Files are stored in directories. A directory may contain no files, or it may contain many hundreds of files. A directory can also contain other directories, allowing you to build up a - hierarchy of directories within one another. This makes it much - easier to organize your data. + hierarchy of directories within one another in order to organize + data. Files and directories are referenced by giving the file or directory name, followed by a forward slash, /, followed by any other directory names that - are necessary. If you have directory foo, - which contains directory bar, which - contains the file readme.txt, then the full - name, or path to the file is - foo/bar/readme.txt. + are necessary. For example, if the directory + foo contains a directory + bar which contains the file + readme.txt, the full name, or + path, to the file is + foo/bar/readme.txt. Note that this is + different from &windows; which uses + \ to separate file and directory + names. &os; does not use drive letters, or other drive names in + the path. For example, you would not type + c:/foo/bar/readme.txt on &os;. Directories and files are stored in a file system. Each file system contains exactly one directory at the very top level, called the root directory for that - file system. This root directory can then contain other - directories. - - So far this is probably similar to any other operating - system you may have used. There are a few differences; for - example, &ms-dos; uses \ to separate file and - directory names, while &macos; uses :. - - FreeBSD does not use drive letters, or other drive names in - the path. You would not write - c:/foo/bar/readme.txt on FreeBSD. - - Instead, one file system is designated the - root file system. The root file system's - root directory is referred to as /. Every - other file system is then mounted under + file system. This root directory can contain other + directories. One file system is designated the + root file system or /. + Every other file system is mounted under the root file system. No matter how many disks you have on your - FreeBSD system, every directory appears to be part of the same + &os; system, every directory appears to be part of the same disk. Suppose you have three file systems, called A, B, and C. Each file system has one root directory, which contains two other directories, called A1, A2 (and likewise B1, B2 and C1, C2). Call A the root file system. If you used - the ls command to view the contents of this - directory you would see two subdirectories, - A1 and A2. The directory - tree looks like this: + ls to view the contents of this directory you + would see two subdirectories, A1 and + A2. The directory tree looks like + this: / | +--- A1 | `--- A2 A file system must be mounted on to a directory in another - file system. So now suppose that you mount file system - B on to the directory A1. - The root directory of B replaces + file system. When mounting file system + B on to the directory A1, + the root directory of B replaces A1, and the directories in B appear accordingly: / | +--- A1 | | | +--- B1 | | | `--- B2 | `--- A2 Any files that are in the B1 or B2 directories can be reached with the path /A1/B1 or /A1/B2 as necessary. Any files that were in /A1 have been temporarily hidden. They will reappear if B is unmounted from A. If B had been mounted on A2 then the diagram would look like this: / | +--- A1 | `--- A2 | +--- B1 | `--- B2 and the paths would be /A2/B1 and /A2/B2 respectively. File systems can be mounted on top of one another. Continuing the last example, the C file system could be mounted on top of the B1 directory in the B file system, leading to this arrangement: / | +--- A1 | `--- A2 | +--- B1 | | | +--- C1 | | | `--- C2 | `--- B2 Or C could be mounted directly on to the A file system, under the A1 directory: / | +--- A1 | | | +--- C1 | | | `--- C2 | `--- A2 | +--- B1 | `--- B2 - If you are familiar with &ms-dos;, this is similar, although - not identical, to the join command. + This is similar, although not identical, to a &ms-dos; + join. - This is not normally something you need to concern yourself - with. Typically you create file systems when installing FreeBSD + Typically you create file systems when installing &os; and decide where to mount them, and then never change them unless you add a new disk. It is entirely possible to have one large root file system, and not need to create any others. There are some drawbacks to this approach, and one advantage. Benefits of Multiple File Systems Different file systems can have different - mount options. For example, with - careful planning, the root file system can be mounted - read-only, making it impossible for you to inadvertently - delete or edit a critical file. Separating user-writable - file systems, such as /home, from other - file systems also allows them to be mounted - nosuid; this option prevents the + mount options. For example, the root + file system can be mounted read-only, making it impossible + for users to inadvertently delete or edit a critical file. + Separating user-writable file systems, such as + /home, from other file systems allows + them to be mounted nosuid. This + option prevents the suid/guid bits on executables stored on the file system from taking effect, possibly improving security. - FreeBSD automatically optimizes the layout of files on a + &os; automatically optimizes the layout of files on a file system, depending on how the file system is being used. So a file system that contains many small files that are written frequently will have a different optimization to one that contains fewer, larger files. By having one big file system this optimization breaks down. - FreeBSD's file systems are very robust should you lose + &os;'s file systems are very robust should you lose power. However, a power loss at a critical point could still damage the structure of the file system. By splitting - your data over multiple file systems it is more likely that - the system will still come up, making it easier for you to - restore from backup as necessary. + data over multiple file systems it is more likely that the + system will still come up, making it easier to restore from + backup as necessary. Benefit of a Single File System File systems are a fixed size. If you create a file - system when you install FreeBSD and give it a specific size, + system when you install &os; and give it a specific size, you may later discover that you need to make the partition bigger. This is not easily accomplished without backing up, recreating the file system with the new size, and then restoring the backed up data. - FreeBSD features the &man.growfs.8; command, which + &os; features the &man.growfs.8; command, which makes it possible to increase the size of file system on the fly, removing this limitation. File systems are contained in partitions. This does not have the same meaning as the common usage of the term partition (for example, &ms-dos; partition), because of &os;'s &unix; heritage. Each partition is identified by a letter from a through to h. Each partition can contain only one file system, which means that file systems are often described by either their typical mount point in the file system hierarchy, or the letter of the partition they are contained in. - FreeBSD also uses disk space for - swap space. Swap space provides FreeBSD - with virtual memory. This allows your + &os; also uses disk space for swap + space to provide + virtual memory. This allows your computer to behave as though it has much more memory than it - actually does. When FreeBSD runs out of memory it moves some of + actually does. When &os; runs out of memory, it moves some of the data that is not currently being used to the swap space, and moves it back in (moving something else out) when it needs it. Some partitions have certain conventions associated with them. Partition Convention a - Normally contains the root file system + Normally contains the root file system. b - Normally contains swap space + Normally contains swap space. c Normally the same size as the enclosing slice. This allows utilities that need to work on the entire - slice (for example, a bad block scanner) to work on the + slice, such as a bad block scanner, to work on the c partition. You would not normally create a file system on this partition. d Partition d used to have a special meaning associated with it, although that is now gone and d may work as any normal partition. Each partition-that-contains-a-file-system is stored in what - FreeBSD calls a slice. Slice is - FreeBSD's term for what the common call partitions, and again, - this is because of FreeBSD's &unix; background. Slices are + &os; calls a slice. Slice is + &os;'s term for what the common call partitions, and again, + this is because of &os;'s &unix; background. Slices are numbered, starting at 1, through to 4. slices partitions dangerously dedicated Slice numbers follow the device name, prefixed with an s, starting at 1. So da0s1 is the first slice on the first SCSI drive. There can only be four physical slices on a disk, but you can have logical slices inside physical slices of the appropriate type. These extended slices are numbered starting at 5, so ad0s5 is the first extended slice on the first IDE disk. These devices are used by file systems that expect to occupy a slice. Slices, dangerously dedicated physical drives, and other drives contain partitions, which are represented as letters from a to h. This letter is appended to the device name, so da0a is the a partition on the first da drive, which is dangerously dedicated. ad1s3e is the fifth partition in the third slice of the second IDE disk drive. Finally, each disk on the system is identified. A disk name starts with a code that indicates the type of disk, and then a number, indicating which disk it is. Unlike slices, disk numbering starts at 0. Common codes that you will see are listed in . - When referring to a partition FreeBSD requires that you also - name the slice and disk that contains the partition, and when - referring to a slice you must also refer to the disk name. - Thus, you refer to a partition by listing the disk name, + When referring to a partition, include the disk name, s, the slice number, and then the partition - letter. Examples are shown in - . + letter. Examples are shown in . shows a - conceptual model of the disk layout that should help make things - clearer. + conceptual model of a disk layout. - In order to install FreeBSD you must first configure the - disk slices, then create partitions within the slice you will - use for FreeBSD, and then create a file system (or swap space) - in each partition, and decide where that file system will be - mounted. + When installing &os;, configure the disk slices, create + partitions within the slice to be used for &os;, create a file + system or swap space in each partition, and decide where each + file system will be mounted. Disk Device Codes Code Meaning ad ATAPI (IDE) disk da SCSI direct access disk acd ATAPI (IDE) CDROM cd SCSI CDROM fd Floppy disk
Sample Disk, Slice, and Partition Names Name Meaning ad0s1a The first partition (a) on the first slice (s1) on the first IDE disk (ad0). da1s2e The fifth partition (e) on the second slice (s2) on the second SCSI disk (da1). Conceptual Model of a Disk - This diagram shows FreeBSD's view of the first IDE disk + This diagram shows &os;'s view of the first IDE disk attached to the system. Assume that the disk is 4 GB in size, and contains two 2 GB slices (&ms-dos; partitions). The first slice contains a &ms-dos; disk, C:, and the second slice contains a - FreeBSD installation. This example FreeBSD installation has + &os; installation. This example &os; installation has three data partitions, and a swap partition. The three partitions will each hold a file system. Partition a will be used for the root file - system, e for the /var - directory hierarchy, and f for the - /usr directory hierarchy. + system, e for the /var/ directory hierarchy, and + f for the /usr/ directory + hierarchy. .-----------------. --. | | | | DOS / Windows | | : : > First slice, ad0s1 : : | | | | :=================: ==: --. | | | Partition a, mounted as / | | | > referred to as ad0s2a | | | | | :-----------------: ==: | | | | Partition b, used as swap | | | > referred to as ad0s2b | | | | | :-----------------: ==: | Partition c, no | | | Partition e, used as /var > file system, all | | > referred to as ad0s2e | of FreeBSD slice, | | | | ad0s2c :-----------------: ==: | | | | | : : | Partition f, used as /usr | : : > referred to as ad0s2f | : : | | | | | | | | --' | `-----------------' --' Mounting and Unmounting File Systems The file system is best visualized as a tree, - rooted, as it were, at /. - /dev, /usr, and the + rooted, as it were, at /. + /dev, + /usr, and the other directories in the root directory are branches, which may have their own branches, such as - /usr/local, and so on. + /usr/local, and so + on. root file system There are various reasons to house some of these - directories on separate file systems. /var - contains the directories log/, - spool/, - and various types of temporary files, and - as such, may get filled up. Filling up the root file system - is not a good idea, so splitting /var from - / is often favorable. + directories on separate file systems. /var contains the directories + log/, + spool/, and various types + of temporary files, and as such, may get filled up. Filling up + the root file system is not a good idea, so splitting /var from + / is often + favorable. Another common reason to contain certain directory trees on other file systems is if they are to be housed on separate physical disks, or are separate virtual disks, such as Network File System mounts, or CDROM drives. The <filename>fstab</filename> File file systems mounted with fstab During the boot process, file systems listed in /etc/fstab are - automatically mounted (unless they are listed with the - option). - - The /etc/fstab file contains a list - of lines of the following format: + automatically mounted except for the entries containing + . This file contains entries in the + following format: device /mount-point fstype options dumpfreq passno device - A device name (which should exist), as explained in + An existing device name as explained in . mount-point - A directory (which should exist), on which - to mount the file system. + An existing directory on which to mount the file + system. fstype The file system type to pass to &man.mount.8;. The - default FreeBSD file system is + default &os; file system is ufs. options Either for read-write file systems, or for read-only file systems, followed by any other options that may be needed. A common option is for file systems not normally mounted during the boot - sequence. Other options are listed in the &man.mount.8; - manual page. + sequence. Other options are listed in + &man.mount.8;. dumpfreq - This is used by &man.dump.8; to determine which - file systems require dumping. If the field is missing, - a value of zero is assumed. + Used by &man.dump.8; to determine which file systems + require dumping. If the field is missing, a value of + zero is assumed. passno - This determines the order in which file systems - should be checked. File systems that should be skipped - should have their passno set to zero. - The root file system (which needs to be checked before - everything else) should have its - passno set to one, and other file - systems' passno should be set to - values greater than one. If more than one file systems - have the same passno then - &man.fsck.8; will attempt to check file systems in - parallel if possible. + Determines the order in which file systems should be + checked. File systems that should be skipped should + have their passno set to zero. The + root file system needs to be checked before everything + else and should have its passno set + to one. The other file systems should be set to + values greater than one. If more than one file system + has the same passno, &man.fsck.8; + will attempt to check file systems in parallel if + possible. - Consult the &man.fstab.5; manual page for more information - on the format of the /etc/fstab file and - the options it contains. + Refer to &man.fstab.5; for more information on the format + of /etc/fstab and its options. The <command>mount</command> Command file systems mounting - The &man.mount.8; command is what is ultimately used to - mount file systems. - - In its most basic form, you use: + File systems are mounted using &man.mount.8;. The most + basic syntax is as follows: &prompt.root; mount device mountpoint - There are plenty of options, as mentioned in the - &man.mount.8; manual page, but the most common are: + This command provides many options which are described in + &man.mount.8;, The most commonly used options include: Mount Options Mount all the file systems listed in - /etc/fstab. Except those marked as + /etc/fstab, except those marked as noauto, excluded by the flag, or those that are already mounted. Do everything except for the actual mount system call. This option is useful in conjunction with the flag to determine what &man.mount.8; is actually trying to do. Force the mount of an unclean file system - (dangerous), or forces the revocation of write access - when downgrading a file system's mount status from - read-write to read-only. + (dangerous), or the revocation of write access when + downgrading a file system's mount status from read-write + to read-only. Mount the file system read-only. This is identical - to using the - argument to the - option. + to using . fstype - Mount the given file system as the given file system - type, or mount only file systems of the given type, if - given the option. - - ufs is the default file system - type. + Mount the specified file system type or mount only + file systems of the given type, if + is included. ufs is the default file + system type. Update mount options on the file system. Be verbose. Mount the file system read-write. - The option takes a comma-separated - list of the options, including the following: + The following options can be passed to + as a comma-separated list: noexec Do not allow execution of binaries on this file system. This is also a useful security option. nosuid Do not interpret setuid or setgid flags on the file system. This is also a useful security option. The <command>umount</command> Command file systems unmounting - The &man.umount.8; command takes, as a parameter, one of a - mountpoint, a device name, or the or - option. + To unmount a filesystem use &man.umount.8;. This command + takes one parameter which can be a mountpoint, device name, + or . All forms take to force unmounting, and for verbosity. Be warned that - is not generally a good idea. Forcibly - unmounting file systems might crash the computer or damage - data on the file system. - - and are used to - unmount all mounted file systems, possibly modified by the - file system types listed after . - , however, does not attempt to unmount the - root file system. + is not generally a good idea as it might + crash the computer or damage data on the file system. + + To unmount all mounted file systems, or just the file + system types listed after , use + or . Note that + does not attempt to unmount the root file + system. Processes - FreeBSD is a multi-tasking operating system. This means - that it seems as though more than one program is running at - once. Each program running at any one time is called a - process. Every command you run will start - at least one new process, and there are a number of system - processes that run all the time, keeping the system - functional. + &os; is a multi-tasking operating system. Each program + running at any one time is called a + process. Every running command starts + at least one new process and there are a number of system + processes that are run by &os;. Each process is uniquely identified by a number called a - process ID, or - PID, and, like files, each process also - has one owner and group. The owner and group information is - used to determine what files and devices the process can open, - using the file permissions discussed earlier. Most processes - also have a parent process. The parent process is the process - that started them. For example, if you are typing commands to - the shell then the shell is a process, and any commands you run - are also processes. Each process you run in this way will have - your shell as its parent process. The exception to this is a - special process called &man.init.8;. init is - always the first process, so its PID is always 1. - init is started automatically by the kernel - when FreeBSD starts. - - Two commands are particularly useful to see the processes on - the system, &man.ps.1; and &man.top.1;. The - ps command is used to show a static list of - the currently running processes, and can show their PID, how - much memory they are using, the command line they were started - with, and so on. The top command displays - all the running processes, and updates the display every few - seconds, so that you can interactively see what your computer is - doing. - - By default, ps only shows you the - commands that are running and are owned by you. For - example: + process ID + (PID). Similar to files, each process + has one owner and group, and the owner and group permissions are + used to determine which files and devices the process can open. + Most processes also have a parent process that started them. + For example, the shell is a process, and any command started in + the shell is a process which has the shell as its parent + process. The exception is a special process called + &man.init.8; which is always the first process to start at boot + time and which always has a PID of 1. + + To see the processes on the system, use &man.ps.1; and + &man.top.1;. To display a static list of the currently running + processes, their PIDs, how much memory they are using, and the + command they were started with, use ps. To + display all the running processes and update the display every + few seconds so that you can interactively see what the computer + is doing, use top. + + By default, ps only shows the commands + that are running and owned by the user. For example: &prompt.user; ps PID TT STAT TIME COMMAND 298 p0 Ss 0:01.10 tcsh 7078 p0 S 2:40.88 xemacs mdoc.xsl (xemacs-21.1.14) 37393 p0 I 0:03.11 xemacs freebsd.dsl (xemacs-21.1.14) 48630 p0 S 2:50.89 /usr/local/lib/netscape-linux/navigator-linux-4.77.bi -48730 p0 IW 0:00.00 (dns helper) (navigator-linux-) 72210 p0 R+ 0:00.00 ps 390 p1 Is 0:01.14 tcsh 7059 p2 Is+ 1:36.18 /usr/local/bin/mutt -y 6688 p3 IWs 0:00.00 tcsh 10735 p4 IWs 0:00.00 tcsh 20256 p5 IWs 0:00.00 tcsh 262 v0 IWs 0:00.00 -tcsh (tcsh) 270 v0 IW+ 0:00.00 /bin/sh /usr/X11R6/bin/startx -- -bpp 16 280 v0 IW+ 0:00.00 xinit /home/nik/.xinitrc -- -bpp 16 284 v0 IW 0:00.00 /bin/sh /home/nik/.xinitrc 285 v0 S 0:38.45 /usr/X11R6/bin/sawfish - As you can see in this example, the output from &man.ps.1; - is organized into a number of columns. PID - is the process ID discussed earlier. PIDs are assigned starting - from 1, go up to 99999, and wrap around back to the beginning - when you run out (a PID is not reassigned if it is already in - use). The TT column shows the tty the - program is running on, and can safely be ignored for the moment. - STAT shows the program's state, and again, - can be safely ignored. TIME is the amount of - time the program has been running on the CPU—this is - usually not the elapsed time since you started the program, as + The output from &man.ps.1; is organized into a number of + columns. The PID column displays the process + ID. PIDs are assigned starting at 1, go up to 99999, then wrap + around back to the beginning. However, a PID is not reassigned + if it is already in use. The TT column shows + the tty the program is running on and STAT + shows the program's state. TIME is the + amount of time the program has been running on the CPU. This is + usually not the elapsed time since the program was started, as most programs spend a lot of time waiting for things to happen before they need to spend time on the CPU. Finally, - COMMAND is the command line that was used to - run the program. + COMMAND is the command that was used to start + the program. &man.ps.1; supports a number of different options to change the information that is displayed. One of the most useful sets is auxww. displays - information about all the running processes, not just your own. + information about all the running processes of all users. displays the username of the process' owner, as well as memory usage. displays information about daemon processes, and causes &man.ps.1; to display the full command line for each process, rather than truncating it once it gets too long to fit on the screen. The output from &man.top.1; is similar. A sample session looks like this: &prompt.user; top last pid: 72257; load averages: 0.13, 0.09, 0.03 up 0+13:38:33 22:39:10 47 processes: 1 running, 46 sleeping CPU states: 12.6% user, 0.0% nice, 7.8% system, 0.0% interrupt, 79.7% idle Mem: 36M Active, 5256K Inact, 13M Wired, 6312K Cache, 15M Buf, 408K Free Swap: 256M Total, 38M Used, 217M Free, 15% Inuse PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND 72257 nik 28 0 1960K 1044K RUN 0:00 14.86% 1.42% top 7078 nik 2 0 15280K 10960K select 2:54 0.88% 0.88% xemacs-21.1.14 281 nik 2 0 18636K 7112K select 5:36 0.73% 0.73% XF86_SVGA 296 nik 2 0 3240K 1644K select 0:12 0.05% 0.05% xterm 48630 nik 2 0 29816K 9148K select 3:18 0.00% 0.00% navigator-linu 175 root 2 0 924K 252K select 1:41 0.00% 0.00% syslogd 7059 nik 2 0 7260K 4644K poll 1:38 0.00% 0.00% mutt ... The output is split into two sections. The header (the first five lines) shows the PID of the last process to run, the system load averages (which are a measure of how busy the system is), the system uptime (time since the last reboot) and the current time. The other figures in the header relate to how many processes are running (47 in this case), how much memory - and swap space has been taken up, and how much time the system - is spending in different CPU states. - - Below that are a series of columns containing similar - information to the output from &man.ps.1;. As before you can - see the PID, the username, the amount of CPU time taken, and the - command that was run. &man.top.1; also defaults to showing you - the amount of memory space taken by the process. This is split - into two columns, one for total size, and one for resident - size—total size is how much memory the application has - needed, and the resident size is how much it is actually using - at the moment. In this example you can see that - &netscape; has required almost - 30 MB of RAM, but is currently only using 9 MB. - - &man.top.1; automatically updates this display every two - seconds; this can be changed with the - option. + and swap space has been used, and how much time the system is + spending in different CPU states. + + Below the header is a series of columns containing similar + information to the output from &man.ps.1;, such as the PID, + username, amount of CPU time, and the command that started the + process. By default, &man.top.1; also displays the amount of + memory space taken by the process. This is split into two + columns: one for total size and one for resident size. Total + size is how much memory the application has needed and the + resident size is how much it is actually using at the moment. + In this example, &netscape; has + required almost 30 MB of RAM, but is currently only using + 9 MB. + + &man.top.1; automatically updates the display every two + seconds. A different interval can be specified with + . Daemons, Signals, and Killing Processes - When you run an editor it is easy to control the editor, - tell it to load files, and so on. You can do this because the - editor provides facilities to do so, and because the editor is - attached to a terminal. Some programs - are not designed to be run with continuous user input, and so - they disconnect from the terminal at the first opportunity. For - example, a web server spends all day responding to web requests, - it normally does not need any input from you. Programs that - transport email from site to site are another example of this - class of application. - - We call these programs daemons. - Daemons were characters in Greek mythology: neither good or - evil, they were little attendant spirits that, by and large, did - useful things for mankind, much like the web servers and mail - servers of today do useful things. This is why the BSD mascot - has, for a long time, been the cheerful-looking daemon with - sneakers and a pitchfork. + When using an editor, it is easy to control the editor and + load files because the editor provides facilities to do so, and + because the editor is attached to a + terminal. Some programs are not designed + to be run with continuous user input and disconnect from the + terminal at the first opportunity. For example, a web server + responds to web requests, rather than user input. Mail servers + are another example of this type of application. + + These programs are known as daemons. + The term daemon comes from Greek mythology and represents an + entity that is neither good or evil, and which invisibly + performs useful tasks. This is why the BSD mascot is the + cheerful-looking daemon with sneakers and a pitchfork. There is a convention to name programs that normally run as daemons with a trailing d. BIND is the Berkeley Internet Name - Domain, but the actual program that executes is called - named; the Apache - web server program is called httpd; the line - printer spooling daemon is lpd and so on. - This is a convention, not a hard and fast rule; for example, the - main mail daemon for the Sendmail - application is called sendmail, and not - maild, as you might imagine. - - Sometimes you will need to communicate with a daemon - process. One way to do so is to send it (or any other running - process), what is known as a signal. - There are a number of different signals that you can - send—some of them have a specific meaning, others are - interpreted by the application, and the application's - documentation will tell you how that application interprets - signals. You can only send a signal to a process that you own. - If you send a signal to someone else's process with &man.kill.1; - or &man.kill.2;, permission will be denied. The exception to - this is the root user, who can send signals - to everyone's processes. - - FreeBSD will also send applications signals in some cases. - If an application is badly written, and tries to access memory - that it is not supposed to, FreeBSD sends the process the + Domain, but the actual program that executes is + named. The Apache + web server program is httpd and the + line printer spooling daemon is lpd. This is + only a naming convention. For example, the main mail daemon for + the Sendmail application is + sendmail, and not + maild. + + One way to communicate with a daemon, or any running + process, is to send a signal using + &man.kill.1;. There are a number of different signals; some + have a specific meaning while others are described in the + application's documentation. A user can only send a signal to a + process they own and sending a signal to someone else's process + will result in a permission denied error. The exception is the + root user, who can send signals to anyone's + processes. + + &os; can also send a signal to a process. If an application + is badly written and tries to access memory that it is not + supposed to, &os; will send the process the Segmentation Violation signal (SIGSEGV). If an application has used the &man.alarm.3; system call to be alerted after a period of time - has elapsed then it will be sent the Alarm signal - (SIGALRM), and so on. + has elapsed, it will be sent the Alarm signal + (SIGALRM). - Two signals can be used to stop a process, + Two signals can be used to stop a process: SIGTERM and SIGKILL. - SIGTERM is the polite way to kill a process; - the process can catch the signal, realize - that you want it to shut down, close any log files it may have - open, and generally finish whatever it is doing at the time - before shutting down. In some cases a process may even ignore + SIGTERM is the polite way to kill a process + as the process can read the signal, close any log files it may + have open, and attempt to finish what it is doing before + shutting down. In some cases, a process may ignore SIGTERM if it is in the middle of some task that can not be interrupted. SIGKILL can not be ignored by a process. This is the I do not care what you are doing, stop right - now signal. If you send SIGKILL to a - process then FreeBSD will stop that process there and - then - Not quite true—there are a few things that can not - be interrupted. For example, if the process is trying to - read from a file that is on another computer on the network, - and the other computer has gone away for some reason (been - turned off, or the network has a fault), then the process is - said to be uninterruptible. Eventually the - process will time out, typically after two minutes. As soon - as this time out occurs the process will be killed. + now signal. Sending a SIGKILL to a + process will usually stop that process there and then. + There are a few tasks that can not be interrupted. For + example, if the process is trying to read from a file that + is on another computer on the network, and the other + computer is unavailable, the process is said to be + uninterruptible. Eventually the process will + time out, typically after two minutes. As soon as this time + out occurs the process will be killed. . - The other signals you might want to use are - SIGHUP, SIGUSR1, and - SIGUSR2. These are general purpose signals, - and different applications will do different things when they - are sent. - - Suppose that you have changed your web server's - configuration file—you would like to tell the web server - to re-read its configuration. You could stop and restart - httpd, but this would result in a brief - outage period on your web server, which may be undesirable. - Most daemons are written to respond to the - SIGHUP signal by re-reading their - configuration file. So instead of killing and restarting - httpd you would send it the - SIGHUP signal. Because there is no standard - way to respond to these signals, different daemons will have - different behavior, so be sure and read the documentation for - the daemon in question. - - Signals are sent using the &man.kill.1; command, as this - example shows. + Other commonly used signals are SIGHUP, + SIGUSR1, and SIGUSR2. + These are general purpose signals and different applications + will respond differently. + + For example, after changing a web server's configuration + file, the web server needs to be told to re-read its + configuration. Restarting httpd would result + in a brief outage period on the web server. Instead, send the + daemon the SIGHUP signal. Be aware that + different daemons will have different behavior, so refer to the + documentation for the daemon to determine if + SIGHUP will achieve the desired + results. Sending a Signal to a Process This example shows how to send a signal to &man.inetd.8;. The inetd configuration file is /etc/inetd.conf, and inetd will re-read this configuration file - when it is sent SIGHUP. + when it is sent a SIGHUP. - Find the process ID of the process you want to send the - signal to. Do this using &man.pgrep.1;. + Find the PID of the process you want to send the signal + to using &man.pgrep.1;. In this example, the PID for + &man.inetd.8; is 198: &prompt.user; pgrep -l inetd 198 inetd -wW - So the &man.inetd.8; PID is 198. Use &man.kill.1; to send the signal. Because - &man.inetd.8; is being run by root you - must use &man.su.1; to become root - first. + &man.inetd.8; is owned by root, use + &man.su.1; to become root first. &prompt.user; su Password: &prompt.root; /bin/kill -s HUP 198 - In common with most &unix; commands, &man.kill.1; will - not print any output if it is successful. If you send a - signal to a process that you do not own then you will see + Like most &unix; commands, &man.kill.1; will not print + any output if it is successful. If you send a signal to a + process that you do not own, you will instead see kill: PID: Operation - not permitted. If you mistype the PID you - will either send the signal to the wrong process, which - could be bad, or, if you are lucky, you will have sent the - signal to a PID that is not currently in use, and you will - see kill: PID: No such + not permitted. Mistyping the PID will either + send the signal to the wrong process, which could have + negative results, or will send the signal to a PID that is + not currently in use, resulting in the error + kill: PID: No such process. Why Use <command>/bin/kill</command>? - Many shells provide the kill - command as a built in command; that is, the shell will - send the signal directly, rather than running - /bin/kill. This can be very useful, - but different shells have a different syntax for - specifying the name of the signal to send. Rather than - try to learn all of them, it can be simpler just to use - the /bin/kill - ... command + Many shells provide kill as a built + in command, meaning that the shell will send the signal + directly, rather than running + /bin/kill. Be aware that different + shells have a different syntax for specifying the name of + the signal to send. Rather than try to learn all of them, + it can be simpler to use /bin/kill + ... directly. - Sending other signals is very similar, just substitute + When sending other signals, substitute TERM or KILL in the command line as necessary. - Killing random process on the system can be a bad idea. - In particular, &man.init.8;, process ID 1, is very special. - Running /bin/kill -s KILL 1 is a quick way - to shutdown your system. Always double - check the arguments you run &man.kill.1; with - before you press + Killing a random process on the system can be a bad idea. + In particular, &man.init.8;, PID 1, is special. Running + /bin/kill -s KILL 1 is a quick, and + unrecommended, way to shutdown the system. + Always double check the arguments to + &man.kill.1; before pressing Return. Shells shells command line - In FreeBSD, a lot of everyday work is done in a command line - interface called a shell. A shell's main job is to take - commands from the input channel and execute them. A lot of - shells also have built in functions to help with everyday tasks - such as file management, file globbing, command line editing, - command macros, and environment variables. FreeBSD comes with a - set of shells, such as sh, the Bourne Shell, - and tcsh, the improved C-shell. Many other - shells are available from the FreeBSD Ports Collection, such as - zsh and bash. - - Which shell do you use? It is really a matter of taste. If - you are a C programmer you might feel more comfortable with a - C-like shell such as tcsh. If you have come - from Linux or are new to a &unix; command line interface you - might try bash. The point is that each shell - has unique properties that may or may not work with your - preferred working environment, and that you have a choice of - what shell to use. - - One common feature in a shell is filename completion. Given - the typing of the first few letters of a command or filename, - you can usually have the shell automatically complete the rest - of the command or filename by hitting the Tab - key on the keyboard. Here is an example. Suppose you have two + &os; provides a command line interface called a shell. A + shell receives commands from the input channel and executes + them. Many shells provide built in functions to help with + everyday tasks such as file management, file globbing, command + line editing, command macros, and environment variables. &os; + comes with several shells, including sh, the + Bourne Shell, and tcsh, the improved C-shell. + Other shells are available from the &os; Ports Collection, such + as zsh and bash. + + The shell that is used is really a matter of taste. A C + programmer might feel more comfortable with a C-like shell such + as tcsh. A Linux user might prefer + bash. Each shell has unique properties that + may or may not work with a user's preferred working environment, + which is why there is a choice of which shell to use. + + One common shell feature is filename completion. After a + user types the first few letters of a command or filename and + presses Tab, the shell will automatically + complete the rest of the command or filename. Consider two files called foobar and - foo.bar. You want to delete - foo.bar. So what you would type on the - keyboard is: rm + foo.bar. To delete + foo.bar, type rm fo[Tab].[Tab]. - The shell would print out - rm foo[BEEP].bar. + The shell should print out rm + foo[BEEP].bar. - The [BEEP] is the console bell, which is the shell telling - me it was unable to totally complete the filename because there + The [BEEP] is the console bell, which the shell used to + indicate it was unable to complete the filename because there is more than one match. Both foobar and - foo.bar start with fo, - but it was able to complete to foo. If you - type in ., then hit Tab - again, the shell would be able to fill in the rest of the - filename for you. + foo.bar start with fo. + By typing ., then pressing + Tab again, the shell would be able to fill in + the rest of the filename. environment variables Another feature of the shell is the use of environment variables. Environment variables are a variable/key pair stored - in the shell's environment space. This space can be read by any + in the shell's environment. This environment can be read by any program invoked by the shell, and thus contains a lot of program configuration. Here is a list of common environment variables - and what they mean: + and their meanings: environment variables Variable Description USER Current logged in user's name. PATH Colon-separated list of directories to search for binaries. DISPLAY - Network name of the X11 display to connect to, if - available. + Network name of the Xorg + display to connect to, if available. SHELL The current shell. TERM The name of the user's type of terminal. Used to determine the capabilities of the terminal. TERMCAP Database entry of the terminal escape codes to perform various terminal functions. OSTYPE - Type of operating system. e.g., FreeBSD. + Type of operating system. MACHTYPE - The CPU architecture that the system is running - on. + The system's CPU architecture. EDITOR The user's preferred text editor. PAGER The user's preferred text pager. MANPATH Colon-separated list of directories to search for manual pages. Bourne shells - Setting an environment variable differs somewhat from - shell to shell. For example, in the C-Style shells such as - tcsh and csh, you would - use setenv to set environment variables. - Under Bourne shells such as sh and - bash, you would use export - to set your current environment variables. For example, to set - or modify the EDITOR environment variable, under - csh or tcsh a command like - this would set EDITOR to - /usr/local/bin/emacs: + How to set an environment variable differs between shells. + In tcsh and csh, use + setenv to set environment variables. In + sh and bash, use + export to set the current environment + variables. This example sets the default EDITOR + to /usr/local/bin/emacs for the + tcsh shell: &prompt.user; setenv EDITOR /usr/local/bin/emacs - Under Bourne shells: + The equivalent command for bash + would be: &prompt.user; export EDITOR="/usr/local/bin/emacs" - You can also make most shells expand the environment - variable by placing a $ character in front of - it on the command line. For example, - echo $TERM would print out whatever - $TERM is set to, because the shell expands - $TERM and passes it on to - echo. - - Shells treat a lot of special characters, called - meta-characters as special representations of data. The most - common one is the * character, which - represents any number of characters in a filename. These - special meta-characters can be used to do filename globbing. - For example, typing in echo * is almost the - same as typing in ls because the shell takes - all the files that match * and puts them on - the command line for echo to see. - - To prevent the shell from interpreting these special - characters, they can be escaped from the shell by putting a - backslash (\) character in front of them. - echo $TERM prints whatever your terminal is - set to. echo \$TERM prints - $TERM as is. + To expand an environment variable in order to see its + current setting, type a $ character in front + of its name on the command line. For example, + echo $TERM displays the current + $TERM setting. + + Shells treat special characters, known as meta-characters, + as special representations of data. The most common + meta-character is *, which + represents any number of characters in a filename. + Meta-characters can be used to perform filename globbing. For + example, echo * is equivalent to + ls because the shell takes all the files that + match * and echo lists + them on the command line. + + To prevent the shell from interpreting a special character, + escape it from the shell by starting it with a backslash + (\). For example, + echo $TERM prints the terminal setting + whereas echo \$TERM literally prints the + string $TERM. Changing Your Shell - The easiest way to change your shell is to use the - chsh command. Running - chsh will place you into the editor that is - in your EDITOR environment variable; if it is - not set, you will be placed in vi. Change - the Shell: line accordingly. + The easiest way to permanently change the default shell is + to use chsh. Running this command will + open the editor that is configured in the + EDITOR environment variable, which by default + is set to vi. Change + the Shell: line to the full path of the + new shell. - You can also give chsh the - option; this will set your shell for you, - without requiring you to enter an editor. For example, if you - wanted to change your shell to bash, the - following should do the trick: + Alternately, use chsh -s which will set + the specified shell without opening an editor. For example, + to change the shell to bash: &prompt.user; chsh -s /usr/local/bin/bash - The shell that you wish to use must - be present in the /etc/shells file. If - you have installed a shell from the - ports collection, then this - should have been done for you already. If you installed the - shell by hand, you must do this. - - For example, if you installed bash by - hand and placed it into /usr/local/bin, - you would want to: + The new shell must be present in + /etc/shells. If the shell was + installed from the &os; Ports + Collection, it should be automatically added to + this file. If it is missing, add it using this + command, replacing the path with the path of the + shell: - &prompt.root; echo "/usr/local/bin/bash" >> /etc/shells + &prompt.root; echo /usr/local/bin/bash >> /etc/shells Then rerun chsh. Text Editors text editors editors - A lot of configuration in FreeBSD is done by editing text - files. Because of this, it would be a good idea to become - familiar with a text editor. FreeBSD comes with a few as part - of the base system, and many more are available in the Ports - Collection. + Most &os; configuration is done by editing text files. + Because of this, it is a good idea to become familiar with a + text editor. &os; comes with a few as part of the base system, + and many more are available in the Ports Collection. ee editors ee - The easiest and simplest editor to learn is an editor called - ee, which stands for easy editor. To - start ee, one would type at the - command line + A simple editor to learn is ee, + which stands for easy editor. To start this editor, type ee filename where filename is the name of the file to - be edited. For example, to edit - /etc/rc.conf, type in - ee /etc/rc.conf. Once inside of - ee, all of the commands for manipulating the - editor's functions are listed at the top of the display. The - caret ^ character represents the - Ctrl key on the keyboard, so - ^e expands to the key combination ^ represents + Ctrl, so ^e expands to + Ctrle. - To leave ee, hit the - Esc key, then choose leave editor. The editor - will prompt you to save any changes if the file has been + To leave ee, press + Esc, then choose the leave + editor option from the main menu. The editor will + prompt you to save any changes if the file has been modified. vi editors vi emacs editors emacs - FreeBSD also comes with more powerful text editors such as - vi as part of the base system, while - other editors, like Emacs and - vim, are part of the FreeBSD Ports - Collection (editors/emacs - and editors/vim). These - editors offer much more functionality and power at the expense - of being a little more complicated to learn. However if you - plan on doing a lot of text editing, learning a more powerful - editor such as vim or - Emacs will save you much more time in - the long run. + &os; also comes with more powerful text editors such as + vi as part of the base system. + Other editors, like editors/emacs and + editors/vim, are part of the + &os; Ports Collection. These editors offer more functionality + at the expense of being a more complicated to learn. Learning a + more powerful editor such as vim or + Emacs can save more time in the long + run. Many applications which modify files or require typed input will automatically open a text editor. To alter the default editor used, set the EDITOR environment - variable. See shells - section for more details. + variable as described in the shells section. Devices and Device Nodes A device is a term used mostly for hardware-related activities in a system, including disks, printers, graphics - cards, and keyboards. When FreeBSD boots, the majority - of what FreeBSD displays are devices being detected. - You can look through the boot messages again by viewing + cards, and keyboards. When &os; boots, the majority of the boot + messages refer to devices being detected. A copy of the boot + messages are saved to /var/run/dmesg.boot. - For example, acd0 is the - first IDE CDROM drive, while kbd0 - represents the keyboard. + Each device has a device name and number. For example, + acd0 is the first IDE CD-ROM drive, + while kbd0 represents the + keyboard. - Most of these devices in a &unix; operating system must be - accessed through special files called device nodes, which are - located in the /dev directory. + Most devices in a &os; must be accessed through special + files called device nodes, which are located in + /dev. Creating Device Nodes When adding a new device to your system, or compiling in support for additional devices, new device nodes must be created. <literal>DEVFS</literal> (DEVice File System) - The device file system, or DEVFS, - provides access to kernel's device namespace in the global - file system namespace. Instead of having to create and - modify device nodes, DEVFS maintains this - particular file system for you. - - See the &man.devfs.5; manual page for more - information. + The device file system, DEVFS, + provides access to the kernel's device namespace in the + global file system namespace. Instead of having to + manually create and modify device nodes, + DEVFS automatically maintains this + particular file system. Refer to &man.devfs.5; for + more information. Binary Formats - To understand why &os; uses the &man.elf.5; - format, you must first know a little about the three currently - dominant executable formats for &unix;: + To understand why &os; uses the &man.elf.5; format,the three + currently dominant executable formats for &unix; + must be described: &man.a.out.5; The oldest and classic &unix; object - format. It uses a short and compact header with a magic - number at the beginning that is often used to characterize - the format (see &man.a.out.5; for more details). It - contains three loaded segments: .text, .data, and .bss plus - a symbol table and a string table. + format. It uses a short and compact header with a + &man.magic.5; number at the beginning that is often used to + characterize the format. It contains three loaded segments: + .text, .data, and .bss, plus a symbol table and a string + table. COFF - The SVR3 object format. The header now comprises a - section table, so you can have more than just .text, .data, - and .bss sections. + The SVR3 object format. The header comprises a section + table which can contain more than just .text, .data, and + .bss sections. &man.elf.5; The successor to COFF, featuring multiple sections and 32-bit or 64-bit possible values. One - major drawback: ELF was also designed + major drawback is that ELF was designed with the assumption that there would be only one ABI per - system architecture. That assumption is actually quite - incorrect, and not even in the commercial SYSV world (which - has at least three ABIs: SVR4, Solaris, SCO) does it hold + system architecture. That assumption is actually incorrect, + and not even in the commercial SYSV world (which has at + least three ABIs: SVR4, Solaris, SCO) does it hold true. - FreeBSD tries to work around this problem somewhat by + &os; tries to work around this problem somewhat by providing a utility for branding a known ELF executable with information - about the ABI it is compliant with. See the manual page for - &man.brandelf.1; for more information. + about its compliant ABI. Refer to &man.brandelf.1; for more + information. - FreeBSD comes from the classic camp and used + &os; comes from the classic camp and used the &man.a.out.5; format, a technology tried and proven through many generations of BSD releases, until the beginning of the 3.X branch. Though it was possible to build and run native - ELF binaries (and kernels) on a FreeBSD - system for some time before that, FreeBSD initially resisted the + ELF binaries and kernels on a &os; + system for some time before that, &os; initially resisted the push to switch to ELF as the - default format. Why? Well, when the Linux camp made their - painful transition to ELF, it was not so much - to flee the a.out executable format as it - was their inflexible jump-table based shared library mechanism, - which made the construction of shared libraries very difficult - for vendors and developers alike. Since the - ELF tools available offered a solution to the - shared library problem and were generally seen as the way - forward anyway, the migration cost was accepted as - necessary and the transition made. FreeBSD's shared library - mechanism is based more closely on Sun's - &sunos; style shared library mechanism - and, as such, is very easy to use. - - So, why are there so many different formats? - - Back in the dim, dark past, there was simple hardware. This - simple hardware supported a simple, small system. - a.out was completely adequate for the job - of representing binaries on this simple system (a PDP-11). As - people ported &unix; from this simple system, they retained the - a.out format because it was sufficient for - the early ports of &unix; to architectures like the Motorola - 68k, VAXen, etc. - - Then some bright hardware engineer decided that if he could - force software to do some sleazy tricks, then he would be able - to shave a few gates off the design and allow his CPU core to - run faster. While it was made to work with this new kind of - hardware (known these days as RISC), - a.out was ill-suited for this hardware, so - many formats were developed to get to a better performance from - this hardware than the limited, simple - a.out format could offer. Things like + default format. Why? When Linux made its painful transition to + ELF, it was due to their inflexible + jump-table based shared library mechanism, which made the + construction of shared libraries difficult for vendors and + developers. Since ELF tools offered a + solution to the shared library problem and were generally seen + as the way forward, the migration cost was + accepted as necessary and the transition made. &os;'s shared + library mechanism is based more closely on the &sunos; style + shared library mechanism and is easy to use. + + So, why are there so many different formats? Back in the + PDP-11 days when simple hardware supported a simple, small + system, a.out was adequate for the job of + representing binaries. As &unix; was ported, the + a.out format was retained because it was + sufficient for the early ports of &unix; to architectures like + the Motorola 68k or VAXen. + + Then some hardware engineer decided that if he could force + software to do some sleazy tricks, a few gates could be shaved + off the design and the CPU core could run faster. + a.out was ill-suited for this new kind of + hardware, known as RISC. Many formats were + developed to get better performance from this hardware than the + limited, simple a.out format could offer. COFF, ECOFF, and a few - obscure others were invented and their limitations explored - before things seemed to settle on ELF. - - In addition, program sizes were getting huge and disks (and - physical memory) were still relatively small so the concept of a - shared library was born. The VM system also became more - sophisticated. While each one of these advancements was done - using the a.out format, its usefulness was - stretched more and more with each new feature. In addition, - people wanted to dynamically load things at run time, or to junk - parts of their program after the init code had run to save in - core memory and swap space. Languages became more sophisticated - and people wanted code called before main automatically. Lots - of hacks were done to the a.out format to - allow all of these things to happen, and they basically worked - for a time. In time, a.out was not up to - handling all these problems without an ever increasing overhead - in code and complexity. While ELF solved - many of these problems, it would be painful to switch from the - system that basically worked. So ELF had to - wait until it was more painful to remain with - a.out than it was to migrate to + others were invented and their limitations explored before + settling on ELF. + + In addition, program sizes were getting huge while disks + and physical memory were still relatively small, so the concept + of a shared library was born. The virtual memory system became + more sophisticated. While each advancement was done using the + a.out format, its usefulness was stretched + with each new feature. In addition, people wanted to + dynamically load things at run time, or to junk parts of their + program after the init code had run to save in core memory and + swap space. Languages became more sophisticated and people + wanted code called before the main() function automatically. + Lots of hacks were done to the a.out format + to allow all of these things to happen, and they basically + worked for a time. In time, a.out was not + up to handling all these problems without an ever increasing + overhead in code and complexity. While ELF + solved many of these problems, it would be painful to switch + from the system that basically worked. So + ELF had to wait until it was more painful to + remain with a.out than it was to migrate to ELF. - However, as time passed, the build tools that FreeBSD - derived their build tools from (the assembler and loader - especially) evolved in two parallel trees. The FreeBSD tree - added shared libraries and fixed some bugs. The GNU folks that - originally wrote these programs rewrote them and added simpler - support for building cross compilers, plugging in different - formats at will, and so on. Since many people wanted to build - cross compilers targeting FreeBSD, they were out of luck since - the older sources that FreeBSD had for + As time passed, the build tools that &os; derived their + build tools from, especially the assembler and loader, evolved + in two parallel trees. The &os; tree added shared libraries and + fixed some bugs. The GNU folks that originally wrote these + programs rewrote them and added simpler support for building + cross compilers and plugging in different formats. Those who + wanted to build cross compilers targeting &os; were out of luck + since the older sources that &os; had for as and ld were not up to the task. The new GNU tools chain - (binutils) does support cross - compiling, ELF, shared libraries, C++ - extensions, etc. In addition, many vendors are releasing - ELF binaries, and it is a good thing for - FreeBSD to run them. + (binutils) supports cross + compiling, ELF, shared libraries, and C++ + extensions. In addition, many vendors release + ELF binaries, and &os; should be able to run + them. ELF is more expressive than a.out and allows more extensibility in the base system. The ELF tools are better - maintained, and offer cross compilation support, which is - important to many people. ELF may be a - little slower than a.out, but trying to - measure it can be difficult. There are also numerous details - that are different between the two in how they map pages, handle - init code, etc. None of these are very important, but they are - differences. In time support for a.out - will be moved out of the GENERIC kernel, - and eventually removed from the kernel once the need to run - legacy a.out programs is past. + maintained and offer cross compilation support. + ELF may be a little slower than + a.out, but trying to measure it can be + difficult. There are also numerous details that are different + between the two such as how they map pages and handle init code. + In time, support for a.out will be moved + out of the GENERIC kernel, and eventually + removed from the kernel once the need to run legacy + a.out programs is past. For More Information Manual Pages manual pages - The most comprehensive documentation on FreeBSD is in the + The most comprehensive documentation on &os; is in the form of manual pages. Nearly every program on the system comes with a short reference manual explaining the basic - operation and various arguments. These manuals can be viewed - with the man command. Use of the - man command is simple: + operation and available arguments. These manuals can be + viewed using man: &prompt.user; man command - command is the name of the command you - wish to learn about. For example, to learn more about - ls command type: + where command is the name of + the command you wish to learn about. For example, to learn + more about ls, type: &prompt.user; man ls - The online manual is divided up into numbered + The online manual is divided into numbered sections: User commands. System calls and error numbers. Functions in the C libraries. Device drivers. File formats. Games and other diversions. Miscellaneous information. System maintenance and operation commands. Kernel developers. In some cases, the same topic may appear in more than one section of the online manual. For example, there is a chmod user command and a - chmod() system call. In this case, you - can tell the man command which one you want - by specifying the section: + chmod() system call. To tell + man which section to display, specify the + section number: &prompt.user; man 1 chmod This will display the manual page for the user command chmod. References to a particular section of the online manual are traditionally placed in parenthesis in written documentation, so &man.chmod.1; refers to the chmod user command and &man.chmod.2; refers to the system call. - This is fine if you know the name of the command and just - wish to know how to use it, but what if you cannot recall the - command name? You can use man to search - for keywords in the command descriptions by using the - switch: + If you do not know the command name, use man + -k to search for keywords in the command + descriptions: - &prompt.user; man -k mail + &prompt.user; man -k mail - With this command you will be presented with a list of - commands that have the keyword mail in their - descriptions. This is actually functionally equivalent to - using the apropos command. + This command displays a list of commands that have the + keyword mail in their descriptions. This is + equivalent to using &man.apropos.1;. - So, you are looking at all those fancy commands in - /usr/bin but do not have the faintest - idea what most of them actually do? Type: + To determine what the commands in + /usr/bin do, type: &prompt.user; cd /usr/bin &prompt.user; man -f * or &prompt.user; cd /usr/bin &prompt.user; whatis * - which does the same thing. GNU Info Files Free Software Foundation - FreeBSD includes many applications and utilities produced + &os; includes many applications and utilities produced by the Free Software Foundation (FSF). In addition to manual - pages, these programs come with more extensive hypertext - documents called info files which can be - viewed with the info command or, if you - installed emacs, the info mode of - emacs. + pages, these programs may include hypertext documents called + info files. These can be viewed using + info or, if editors/emacs is installed, the + info mode of emacs. - To use the &man.info.1; command, type: + To use &man.info.1;, type: &prompt.user; info For a brief introduction, type h. For a quick command reference, type ?.