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	diff --git a/en_US.ISO8859-1/books/handbook/basics/chapter.sgml b/en_US.ISO8859-1/books/handbook/basics/chapter.sgml
	index 4e8aa965ec..511d5b7238 100644
	--- a/en_US.ISO8859-1/books/handbook/basics/chapter.sgml
	+++ b/en_US.ISO8859-1/books/handbook/basics/chapter.sgml
	@@ -1,2725 +1,2725 @@
	<!--
	The FreeBSD Documentation Project

	$FreeBSD$
	-->

	<chapter id="basics">
	<chapterinfo>
	<authorgroup>
	<author>
	<firstname>Chris</firstname>
	<surname>Shumway</surname>
	<contrib>Rewritten by </contrib>
	</author>
	</authorgroup>
	<!-- 10 Mar 2000 -->
	</chapterinfo>

	<title>UNIX Basics</title>

	<sect1 id="basics-synopsis">
	<title>Synopsis</title>

	<para>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.</para>

	<para>After reading this chapter, you will know:</para>

	<itemizedlist>
	<listitem>
	<para>How to use the <quote>virtual consoles</quote> of
	FreeBSD.</para>
	</listitem>
	<listitem>
	<para>How &unix; file permissions work along with
	understanding file flags in &os;.</para>
	</listitem>
	<listitem>
	<para>The default &os; file system layout.</para>
	</listitem>
	<listitem>
	<para>The &os; disk organization.</para>
	</listitem>
	<listitem>
	<para>How to mount and unmount file systems.</para>
	</listitem>
	<listitem>
	<para>What processes, daemons, and signals are.</para>
	</listitem>
	<listitem>
	<para>What a shell is, and how to change your default login
	environment.</para>
	</listitem>
	<listitem>
	<para>How to use basic text editors.</para>
	</listitem>
	<listitem>
	<para>What devices and device nodes are.</para>
	</listitem>
	<listitem>
	<para>What binary format is used under &os;.</para>
	</listitem>
	<listitem>
	<para>How to read manual pages for more information.</para>
	</listitem>
	</itemizedlist>

	</sect1>

	<sect1 id="consoles">
	<title>Virtual Consoles and Terminals</title>
	<indexterm><primary>virtual consoles</primary></indexterm>
	<indexterm><primary>terminals</primary></indexterm>

	<para>FreeBSD 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 <quote>terminals</quote> and
	<quote>consoles</quote> are, and how you can use them in FreeBSD.</para>

	<sect2 id="consoles-intro">
	<title>The Console</title>
	<indexterm><primary>console</primary></indexterm>

	<para>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:</para>

	<screen>Additional ABI support:.
	Local package initialization:.
	Additional TCP options:.

	Fri Sep 20 13:01:06 EEST 2002

	FreeBSD/i386 (pc3.example.org) (ttyv0)

	login:</screen>

	<para>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:</para>

	<programlisting>FreeBSD/i386 (pc3.example.org) (ttyv0)</programlisting>

	<para>This line contains some bits of information about the system you
	have just booted. You are looking at a <quote>FreeBSD</quote>
	console, running on an Intel or compatible processor of the x86
	architecture<footnote>
	<para>This is what <literal>i386</literal> means. Note that even if
	you are not running FreeBSD on an Intel 386 CPU, this is going to
	be <literal>i386</literal>. It is not the type of your processor,
	but the processor <quote>architecture</quote> that is shown
	here.</para>
	</footnote>. The name of this machine (every &unix; machine has a
	name) is <hostid>pc3.example.org</hostid>, and you are now looking
	at its system console—the <devicename>ttyv0</devicename>
	terminal.</para>

	<para>Finally, the last line is always:</para>

	<programlisting>login:</programlisting>

	<para>This is the part where you are supposed to type in your
	<quote>username</quote> to log into FreeBSD. The next section
	describes how you can do this.</para>
	</sect2>

	<sect2 id="consoles-login">
	<title>Logging into FreeBSD</title>

	<para>FreeBSD 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.</para>

	<para>Every multiuser system needs some way to distinguish one
	<quote>user</quote> from the rest. In FreeBSD (and all the
	&unix;-like operating systems), this is accomplished by requiring that
	every user must <quote>log into</quote> the system before being able
	to run programs. Every user has a unique name (the
	<quote>username</quote>) and a personal, secret key (the
	<quote>password</quote>). FreeBSD will ask for these two before
	allowing a user to run any programs.</para>

	<indexterm><primary>startup scripts</primary></indexterm>
	<para>Right after FreeBSD boots and finishes running its startup
	scripts<footnote>
	<para>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.</para>
	</footnote>, it will present you with a prompt and ask for a valid
	username:</para>

	<screen>login:</screen>

	<para>For the sake of this example, let us assume that your username is
	<username>john</username>. Type <literal>john</literal> at this prompt and press
	<keycap>Enter</keycap>. You should then be presented with a prompt to
	enter a <quote>password</quote>:</para>

	<screen>login: <userinput>john</userinput>
	Password:</screen>

	<para>Type in <username>john</username>'s password now, and press
	<keycap>Enter</keycap>. The password is <emphasis>not
	echoed!</emphasis> You need not worry about this right now. Suffice
	it to say that it is done for security reasons.</para>

	<para>If you have typed your password correctly, you should by now be
	logged into FreeBSD and ready to try out all the available
	commands.</para>

	<para>You should see the <acronym>MOTD</acronym> or message of
	the day followed by a command prompt (a <literal>#</literal>,
	<literal>$</literal>, or <literal>%</literal> character). This
	indicates you have successfully logged into FreeBSD.</para>
	</sect2>

	<sect2 id="consoles-virtual">
	<title>Multiple Consoles</title>

	<para>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
	<quote>virtual consoles</quote> can be very helpful.</para>

	<para>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.</para>

	<para>Special key combinations have been reserved by FreeBSD for
	switching consoles<footnote>
	<para>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.</para>
	</footnote>. You can use
	<keycombo><keycap>Alt</keycap><keycap>F1</keycap></keycombo>,
	<keycombo><keycap>Alt</keycap><keycap>F2</keycap></keycombo>, through
	<keycombo><keycap>Alt</keycap><keycap>F8</keycap></keycombo> to switch
	to a different virtual console in FreeBSD.</para>

	<para>As you are switching from one console to the next, FreeBSD takes
	care of saving and restoring the screen output. The result is an
	<quote>illusion</quote> of having multiple <quote>virtual</quote>
	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.</para>
	</sect2>

	<sect2 id="consoles-ttys">
	<title>The <filename>/etc/ttys</filename> File</title>

	<para>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
	<filename>/etc/ttys</filename> file.</para>

	<para>You can use the <filename>/etc/ttys</filename> file to configure
	the virtual consoles of FreeBSD. Each uncommented line in this file
	(lines that do not start with a <literal>#</literal> 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
	<literal>ttyv</literal>:</para>

	<programlisting># 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</programlisting>

	<para>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.</para>
	</sect2>

	<sect2 id="consoles-singleuser">
	<title>Single User Mode Console</title>

	<para>A detailed description of what <quote>single user mode</quote> is
	can be found in <xref linkend="boot-singleuser">. 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
	<filename>/etc/ttys</filename> file. Look for the line that starts
	with <literal>console</literal>:</para>

	<programlisting># 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</programlisting>

	<note>
	<para>As the comments above the <literal>console</literal> line
	indicate, you can edit this line and change <literal>secure</literal> to
	<literal>insecure</literal>. If you do that, when FreeBSD boots
	into single user mode, it will still ask for the
	<username>root</username> password.</para>

	<para><emphasis>Be careful when changing this to
	<literal>insecure</literal></emphasis>. If you ever forget
	the <username>root</username> 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.</para>
	</note>
	</sect2>

	<sect2 id="consoles-vidcontrol">
	<title>Changing Console Video Modes</title>

	<para>The FreeBSD console default video mode may be adjusted to
	1024x768, 1280x1024, or any other size supported by your
	graphics chip and monitor. To use a different video mode, you
	first must recompile your kernel and include two additional
	options:</para>

	<programlisting>options VESA
	options SC_PIXEL_MODE</programlisting>

	<para>Once the kernel has been recompiled with these two
	options, you can then determine what video modes are supported
	by your hardware by using the &man.vidcontrol.1; utility. To
	get a list of supported video modes issue the following:</para>

	<screen>&prompt.root; <userinput>vidcontrol -i mode</userinput></screen>

	<para>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 <username>root</username> console:</para>

	<screen>&prompt.root; <userinput>vidcontrol MODE_279</userinput></screen>

	<para>If the new video mode is acceptable, it can be permanently
	set on boot by setting it in the <filename>/etc/rc.conf</filename>
	file:</para>

	<programlisting>allscreens_flags="MODE_279"</programlisting>
	</sect2>
	</sect1>

	<sect1 id="permissions">
	<title>Permissions</title>
	<indexterm><primary>UNIX</primary></indexterm>

	<para>FreeBSD, 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.</para>

	<para>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:</para>

	<indexterm><primary>permissions</primary></indexterm>
	<indexterm>
	<primary>file permissions</primary>
	</indexterm>
	<informaltable frame="none" pgwide="1">
	<tgroup cols="3">
	<thead>
	<row>
	<entry>Value</entry>
	<entry>Permission</entry>
	<entry>Directory Listing</entry>
	</row>
	</thead>

	<tbody>
	<row>
	<entry>0</entry>
	<entry>No read, no write, no execute</entry>
	<entry><literal>---</literal></entry>
	</row>

	<row>
	<entry>1</entry>
	<entry>No read, no write, execute</entry>
	<entry><literal>--x</literal></entry>
	</row>

	<row>
	<entry>2</entry>
	<entry>No read, write, no execute</entry>
	<entry><literal>-w-</literal></entry>
	</row>

	<row>
	<entry>3</entry>
	<entry>No read, write, execute</entry>
	<entry><literal>-wx</literal></entry>
	</row>

	<row>
	<entry>4</entry>
	<entry>Read, no write, no execute</entry>
	<entry><literal>r--</literal></entry>
	</row>

	<row>
	<entry>5</entry>
	<entry>Read, no write, execute</entry>
	<entry><literal>r-x</literal></entry>
	</row>

	<row>
	<entry>6</entry>
	<entry>Read, write, no execute</entry>
	<entry><literal>rw-</literal></entry>
	</row>

	<row>
	<entry>7</entry>
	<entry>Read, write, execute</entry>
	<entry><literal>rwx</literal></entry>
	</row>
	</tbody>
	</tgroup>
	</informaltable>
	<indexterm>
	<primary><command>ls</command></primary>
	</indexterm>
	<indexterm><primary>directories</primary></indexterm>

	<para>You can use the <option>-l</option> 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
	<command>ls -l</command> in an arbitrary directory may show:</para>

	<screen>&prompt.user; <userinput>ls -l</userinput>
	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
	...</screen>

	<para>Here is how the first column of <command>ls -l</command> is
	broken up:</para>

	<screen>-rw-r--r--</screen>

	<para>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 <literal>-</literal>
	indicates a regular file. The next three characters,
	<literal>rw-</literal> in this example, give the permissions for the owner of the
	file. The next three characters, <literal>r--</literal>, give the
	permissions for the group that the file belongs to. The final three
	characters, <literal>r--</literal>, 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
	<literal>644</literal>, where each digit represents the three parts
	of the file's permission.</para>

	<para>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 <filename>/dev</filename> directory.</para>

	<para>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 <quote>cd</quote> (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).</para>

	<para>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
	<emphasis>and</emphasis> execute permissions to the directory
	containing the file.</para>

	<para>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.</para>

	<sect2>
	<sect2info>
	<authorgroup>
	<author>
	<firstname>Tom</firstname>
	<surname>Rhodes</surname>
	<contrib>Contributed by </contrib>
	</author>
	</authorgroup>
	</sect2info>

	<title>Symbolic Permissions</title>
	<indexterm><primary>permissions</primary><secondary>symbolic</secondary></indexterm>

	<para>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:</para>

	<informaltable frame="none" pgwide="1">
	<tgroup cols="3">
	<thead>
	<row>
	<entry>Option</entry>
	<entry>Letter</entry>
	<entry>Represents</entry>
	</row>
	</thead>

	<tbody>
	<row>
	<entry>(who)</entry>
	<entry>u</entry>
	<entry>User</entry>
	</row>

	<row>
	<entry>(who)</entry>
	<entry>g</entry>
	<entry>Group owner</entry>
	</row>

	<row>
	<entry>(who)</entry>
	<entry>o</entry>
	<entry>Other</entry>
	</row>

	<row>
	<entry>(who)</entry>
	<entry>a</entry>
	<entry>All (<quote>world</quote>)</entry>
	</row>

	<row>
	<entry>(action)</entry>
	<entry>+</entry>
	<entry>Adding permissions</entry>
	</row>

	<row>
	<entry>(action)</entry>
	<entry>-</entry>
	<entry>Removing permissions</entry>
	</row>

	<row>
	<entry>(action)</entry>
	<entry>=</entry>
	<entry>Explicitly set permissions</entry>
	</row>

	<row>
	<entry>(permissions)</entry>
	<entry>r</entry>
	<entry>Read</entry>
	</row>

	<row>
	<entry>(permissions)</entry>
	<entry>w</entry>
	<entry>Write</entry>
	</row>

	<row>
	<entry>(permissions)</entry>
	<entry>x</entry>
	<entry>Execute</entry>
	</row>

	<row>
	<entry>(permissions)</entry>
	<entry>t</entry>
	<entry>Sticky bit</entry>
	</row>

	<row>
	<entry>(permissions)</entry>
	<entry>s</entry>
	<entry>Set UID or GID</entry>
	</row>
	</tbody>
	</tgroup>
	</informaltable>

	<para>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
	<replaceable>FILE</replaceable>:</para>

	<screen>&prompt.user; <userinput>chmod go= FILE</userinput></screen>

	<para>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 <quote>world</quote> write permission
	on <replaceable>FILE</replaceable>, then it adds the execute
	permissions for everyone:</para>

	<screen>&prompt.user; <userinput>chmod go-w,a+x <replaceable>FILE</replaceable></userinput></screen>

	<!--
	<para>Most users will not notice this, but it should be pointed out
	that using the octal method will only set or assign permissions to
	a file; it does not add or delete them.</para>
	-->
	</sect2>

	<sect2>
	<sect2info>
	<authorgroup>
	<author>
	<firstname>Tom</firstname>
	<surname>Rhodes</surname>
	<contrib>Contributed by </contrib>
	</author>
	</authorgroup>
	</sect2info>

	<title>&os; File Flags</title>

	<para>In addition to file permissions discussed previously, &os;
	supports the use of <quote>file flags.</quote> These flags
	add an additional level of security and control over files, but
	not directories.</para>

	<para>These file flags add an additional level of control over
	files, helping to ensure that in some cases not even the
	<username>root</username> can remove or alter files.</para>

	<para>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 <filename>file1</filename>,
	issue the following command:</para>

	<screen>&prompt.root; <userinput>chflags sunlink <filename>file1</filename></userinput></screen>

	<para>And to disable the system undeletable flag, simply
	issue the previous command with <quote>no</quote> in
	front of the <option>sunlink</option>. Observe:</para>

	<screen>&prompt.root; <userinput>chflags nosunlink <filename>file1</filename></userinput></screen>

	<para>To view the flags of this file, use the &man.ls.1; command
	with the <option>-lo</option> flags:</para>

	<screen>&prompt.root; <userinput>ls -lo <filename>file1</filename></userinput></screen>

	<para>The output should look like the following:</para>

	<programlisting>-rw-r--r-- 1 trhodes trhodes sunlnk 0 Mar 1 05:54 file1</programlisting>

	<para>Several flags may only added or removed to files by the
	<username>root</username> 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.</para>
	</sect2>

	<sect2>
	<sect2info>
	<authorgroup>
	<author>
	<firstname>Tom</firstname>
	<surname>Rhodes</surname>
	<contrib>Contributed by </contrib>
	</author>
	</authorgroup>
	</sect2info>

	<title>The setuid, setgid, and sticky Permissions</title>

	<para>Other than the permissions already discussed, there are
	three other specific settings that all administrators should
	know about. They are the <literal>setuid</literal>,
	<literal>setgid</literal> and <literal>sticky</literal>
	permissions.</para>

	<para>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.</para>

	<para>The real user ID is the <acronym>UID</acronym> who owns
	or starts the process. The effective <acronym>UID</acronym>
	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
	<username>root</username> user. This is what allows normal
	users to change their passwords without seeing a
	<errorname>Permission Denied</errorname> error.</para>

	<note>
	<para>The <literal>nosuid</literal> &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 <literal>nosuid</literal>
	wrapper may be able to circumvent it; according to the
	&man.mount.8; manual page.</para>
	</note>

	<para>The setuid permission may be set by prefixing a permission
	set with the number four (4) as shown in the following
	example:</para>

	<screen>&prompt.root; <userinput>chmod 4755 suidexample.sh</userinput></screen>

	<para>The permissions on the
	<filename><replaceable>suidexample.sh</replaceable></filename>
	file should now look like the following:</para>

	<programlisting>-rwsr-xr-x 1 trhodes trhodes 63 Aug 29 06:36 suidexample.sh</programlisting>

	<para>It should be noticeable from this example that an
	<literal>s</literal> 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 <command>passwd</command>.</para>

	<para>To view this in real time, open two terminals. On
	one, start the <command>passwd</command> process as a normal
	user. While it waits for a new password, check the process
	table and look at the user information of the
	<command>passwd</command> command.</para>

	<para>In terminal A:</para>

	<screen>Changing local password for trhodes
	Old Password:</screen>

	<para>In terminal B:</para>

	<screen>&prompt.root; <userinput>ps aux \| grep passwd</userinput></screen>

	<screen>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</screen>

	<para>As stated above, the <command>passwd</command> is run
	by a normal user, but is using the effective
	<acronym>UID</acronym> of <username>root</username>.</para>

	<para>The <literal>setgid</literal> permission performs the
	same function as the <literal>setuid</literal> 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.</para>

	<para>To set the <literal>setgid</literal> permission on a
	file, provide the <command>chmod</command> command with a
	leading two (2) as in the following example:</para>

	<screen>&prompt.root; <userinput>chmod 2755 sgidexample.sh</userinput></screen>

	<para>The new setting may be viewed as before, notice the
	<literal>s</literal> is now in the field designated for the
	group permission settings:<para>

	<screen>-rwxr-sr-x 1 trhodes trhodes 44 Aug 31 01:49 sgidexample.sh</screen>

	<note>
	<para>In these examples, even though the shell script in
	question is an executable file, it will not run with
	a different <acronym>EUID</acronym> or effective user ID.
	This is because shell scripts may not access the
	&man.setuid.2; system calls.</para>
	</note>

	<para>The first two special permission bits we discussed
	(the <literal>setuid</literal> and <literal>setgid</literal>
	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
	<literal>sticky bit</literal>.</para>

	<para>The <literal>sticky bit</literal>, 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
	<filename class="directory">/tmp</filename>, by users who do
	not own the file. To utilize this permission, prefix the
	permission with a one (1). For example:</para>

	<screen>&prompt.root; <userinput>chmod 1777 /tmp</userinput></screen>

	<para>Now, it is possible to see the effect by using the
	<command>ls</command> command:</para>

	<screen>&prompt.root; <userinput>ls -al / \| grep tmp</userinput></screen>

	<screen>drwxrwxrwt 10 root wheel 512 Aug 31 01:49 tmp</screen>

	<para>The <literal>sticky bit</literal> permission is
	distinguishable from the <literal>t</literal> at the very
	end of the set.</para>
	</sect2>
	</sect1>

	<sect1 id="dirstructure">
	<title>Directory Structure</title>
	<indexterm><primary>directory hierarchy</primary></indexterm>

	<para>The FreeBSD directory hierarchy is fundamental to obtaining
	an overall understanding of the system. The most important
	concept to grasp is that of the root directory,
	<quote>/</quote>. 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.</para>

	<para>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 <xref linkend="disk-organization">.
	Standard mount points include
	<filename>/usr</filename>, <filename>/var</filename>, <filename>/tmp</filename>,
	<filename>/mnt</filename>, and <filename>/cdrom</filename>. These
	directories are usually referenced to entries in the file
	<filename>/etc/fstab</filename>. <filename>/etc/fstab</filename> is
	a table of various file systems and mount points for reference by the
	system. Most of the file systems in <filename>/etc/fstab</filename>
	are mounted automatically at boot time from the script &man.rc.8;
	unless they contain the <option>noauto</option> option.
	Details can be found in <xref linkend="disks-fstab">.</para>

	<para>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.</para>

	<para>
	<informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	<thead>
	<row>
	<entry>Directory</entry>
	<entry>Description</entry>
	</row>
	</thead>
	<tbody valign="top">
	<row>
	<entry><filename class="directory">/</filename></entry>
	<entry>Root directory of the file system.</entry>
	</row>

	<row>
	<entry><filename class="directory">/bin/</filename></entry>
	<entry>User utilities fundamental to both single-user
	and multi-user environments.</entry>
	</row>

	<row>
	<entry><filename class="directory">/boot/</filename></entry>
	<entry>Programs and configuration files used during
	operating system bootstrap.</entry>
	</row>

	<row>
	<entry><filename class="directory">/boot/defaults/</filename></entry>
	<entry>Default bootstrapping configuration files; see
	&man.loader.conf.5;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/dev/</filename></entry>
	<entry>Device nodes; see &man.intro.4;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/etc/</filename></entry>
	<entry>System configuration files and scripts.</entry>
	</row>

	<row>
	<entry><filename class="directory">/etc/defaults/</filename></entry>
	<entry>Default system configuration files; see &man.rc.8;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/etc/mail/</filename></entry>
	<entry>Configuration files for mail transport agents such
	as &man.sendmail.8;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/etc/namedb/</filename></entry>
	<entry><command>named</command> configuration files; see
	&man.named.8;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/etc/periodic/</filename></entry>
	<entry>Scripts that are run daily, weekly, and monthly,
	via &man.cron.8;; see &man.periodic.8;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/etc/ppp/</filename></entry>
	<entry><command>ppp</command> configuration files; see
	&man.ppp.8;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/mnt/</filename></entry>
	<entry>Empty directory commonly used by system administrators as a
	temporary mount point.</entry>
	</row>

	<row>
	<entry><filename class="directory">/proc/</filename></entry>
	<entry>Process file system; see &man.procfs.5;,
	&man.mount.procfs.8;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/rescue/</filename></entry>
	<entry>Statically linked programs for emergency recovery; see
	&man.rescue.8;.</entry>
	</row>

	<row>
	<entry><filename class="directory">/root/</filename></entry>
	<entry>Home directory for the <username>root</username>
	account.</entry>
	</row>

	<row>
	<entry><filename class="directory">/sbin/</filename></entry>
	<entry>System programs and administration utilities fundamental to
	both single-user and multi-user environments.</entry>
	</row>


	<row>
	<entry><filename class="directory">/tmp/</filename></entry>
	<entry>Temporary files. The contents of
	<filename class="directory">/tmp</filename> are usually NOT
	preserved across a system reboot. A memory-based file system
	is often mounted at
	<filename class="directory">/tmp</filename>.
	This can be automated using the tmpmfs-related variables of
	&man.rc.conf.5; (or with an entry in
	<filename>/etc/fstab</filename>; see &man.mdmfs.8;).</entry>
	</row>


	<row>
	<entry><filename class="directory">/usr/</filename></entry>
	<entry>The majority of user utilities and applications.</entry>
	</row>

	<row>
	<entry><filename class="directory">/usr/bin/</filename></entry>
	<entry>Common utilities, programming tools, and applications.</entry>
	</row>

	<row>
	<entry><filename class="directory">/usr/include/</filename></entry>
	<entry>Standard C include files.</entry>
	</row>

	<row>
	<entry><filename class="directory">/usr/lib/</filename></entry>
	<entry>Archive libraries.</entry>
	</row>


	<row>
	<entry><filename class="directory">/usr/libdata/</filename></entry>
	<entry>Miscellaneous utility data files.</entry>
	</row>

	<row>
	<entry><filename class="directory">/usr/libexec/</filename></entry>
	<entry>System daemons & system utilities (executed by other
	programs).</entry>
	</row>

	<row>
	<entry><filename
	class="directory">/usr/local/</filename></entry>

	<entry>Local executables, libraries, etc. Also used as
	the default destination for the FreeBSD ports
	framework. Within <filename>/usr/local</filename>,
	the general layout sketched out by &man.hier.7; for
	<filename>/usr</filename> should be used. Exceptions
	are the man directory, which is directly under
	<filename>/usr/local</filename> rather than under
	<filename>/usr/local/share</filename>, and the ports
	documentation is in
	<filename>share/doc/<replaceable>port</replaceable></filename>.
	</entry>
	</row>

	<row>
	<entry><filename class="directory">/usr/obj/</filename></entry>
	<entry>Architecture-specific target tree produced by building
	the <filename>/usr/src</filename> tree.</entry>
	</row>

	<row>
	- <entry><filename class="directory">/usr/ports</filename></entry>
	+ <entry><filename class="directory">/usr/ports/</filename></entry>
	<entry>The FreeBSD Ports Collection (optional).</entry>
	</row>

	<row>
	<entry><filename class="directory">/usr/sbin/</filename></entry>
	<entry>System daemons & system utilities (executed by users).</entry>
	</row>

	<row>
	<entry><filename class="directory">/usr/share/</filename></entry>
	<entry>Architecture-independent files.</entry>
	</row>

	<row>
	<entry><filename class="directory">/usr/src/</filename></entry>
	<entry>BSD and/or local source files.</entry>
	</row>

	<row>
	<entry><filename
	class="directory">/usr/X11R6/</filename></entry>
	<entry>X11R6 distribution executables, libraries, etc
	(optional).</entry>
	</row>

	<row>
	<entry><filename class="directory">/var/</filename></entry>
	<entry>Multi-purpose log, temporary, transient, and spool files.
	A memory-based file system is sometimes mounted at
	<filename class="directory">/var</filename>.
	This can be automated using the varmfs-related variables of
	&man.rc.conf.5 (or with an entry in
	<filename>/etc/fstab</filename>; see &man.mdmfs.8;).</entry>
	</row>


	<row>
	<entry><filename class="directory">/var/log/</filename></entry>
	<entry>Miscellaneous system log files.</entry>
	</row>

	<row>
	<entry><filename class="directory">/var/mail/</filename></entry>
	<entry>User mailbox files.</entry>
	</row>

	<row>
	<entry><filename class="directory">/var/spool/</filename></entry>
	<entry>Miscellaneous printer and mail system spooling directories.
	</entry>
	</row>

	<row>
	<entry><filename class="directory">/var/tmp/</filename></entry>
	<entry>Temporary files.
	The files are usually preserved across a system reboot,
	unless <filename class="directory">/var</filename>
	is a memory-based file system.</entry>
	</row>

	<row>
	- <entry><filename>/var/yp</filename></entry>
	+ <entry><filename class="directory">/var/yp/</filename></entry>
	<entry>NIS maps.</entry>
	</row>

	</tbody>
	</tgroup>
	</informaltable>
	</para>

	</sect1>

	<sect1 id="disk-organization">
	<title>Disk Organization</title>

	<para>The smallest unit of organization that FreeBSD uses to find files
	is the filename. Filenames are case-sensitive, which means that
	<filename>readme.txt</filename> and <filename>README.TXT</filename>
	are two separate files. FreeBSD does not use the extension
	(<filename>.txt</filename>) of a file to determine whether the file is
	a program, or a document, or some other form of data.</para>

	<para>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.</para>

	<para>Files and directories are referenced by giving the file or
	directory name, followed by a forward slash, <literal>/</literal>,
	followed by any other directory names that are necessary. If you have
	directory <filename>foo</filename>, which contains directory
	<filename>bar</filename>, which contains the file
	<filename>readme.txt</filename>, then the full name, or
	<firstterm>path</firstterm> to the file is
	<filename>foo/bar/readme.txt</filename>.</para>

	<para>Directories and files are stored in a file system. Each file system
	contains exactly one directory at the very top level, called the
	<firstterm>root directory</firstterm> for that file system. This root
	directory can then contain other directories.</para>

	<para>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
	<literal>\</literal> to separate file and directory names, while &macos;
	uses <literal>:</literal>.</para>

	<para>FreeBSD does not use drive letters, or other drive names in the
	path. You would not write <filename>c:/foo/bar/readme.txt</filename>
	on FreeBSD.</para>

	<para>Instead, one file system is designated the <firstterm>root
	file system</firstterm>. The root file system's root directory is
	referred to as <literal>/</literal>. Every other file system is then
	<firstterm>mounted</firstterm> 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 disk.</para>

	<para>Suppose you have three file systems, called <literal>A</literal>,
	<literal>B</literal>, and <literal>C</literal>. Each file system has
	one root directory, which contains two other directories, called
	<literal>A1</literal>, <literal>A2</literal> (and likewise
	<literal>B1</literal>, <literal>B2</literal> and
	<literal>C1</literal>, <literal>C2</literal>).</para>

	<para>Call <literal>A</literal> the root file system. If you used the
	<command>ls</command> command to view the contents of this directory
	you would see two subdirectories, <literal>A1</literal> and
	<literal>A2</literal>. The directory tree looks like this:</para>

	<mediaobject>
	<imageobject>
	<imagedata fileref="install/example-dir1" format="EPS">
	</imageobject>

	<textobject>
	<literallayout class="monospaced"> /
	\|
	+--- A1
	\|
	`--- A2</literallayout>
	</textobject>
	</mediaobject>

	<para>A file system must be mounted on to a directory in another
	file system. So now suppose that you mount file system
	<literal>B</literal> on to the directory <literal>A1</literal>. The
	root directory of <literal>B</literal> replaces <literal>A1</literal>,
	and the directories in <literal>B</literal> appear accordingly:</para>

	<mediaobject>
	<imageobject>
	<imagedata fileref="install/example-dir2" format="EPS">
	</imageobject>

	<textobject>
	<literallayout class="monospaced"> /
	\|
	+--- A1
	\| \|
	\| +--- B1
	\| \|
	\| `--- B2
	\|
	`--- A2</literallayout>
	</textobject>
	</mediaobject>

	<para>Any files that are in the <literal>B1</literal> or
	<literal>B2</literal> directories can be reached with the path
	<filename>/A1/B1</filename> or <filename>/A1/B2</filename> as
	necessary. Any files that were in <filename>/A1</filename> have been
	temporarily hidden. They will reappear if <literal>B</literal> is
	<firstterm>unmounted</firstterm> from A.</para>

	<para>If <literal>B</literal> had been mounted on <literal>A2</literal>
	then the diagram would look like this:</para>

	<mediaobject>
	<imageobject>
	<imagedata fileref="install/example-dir3" format="EPS">
	</imageobject>

	<textobject>
	<literallayout class="monospaced"> /
	\|
	+--- A1
	\|
	`--- A2
	\|
	+--- B1
	\|
	`--- B2</literallayout>
	</textobject>
	</mediaobject>

	<para>and the paths would be <filename>/A2/B1</filename> and
	<filename>/A2/B2</filename> respectively.</para>

	<para>File systems can be mounted on top of one another. Continuing the
	last example, the <literal>C</literal> file system could be mounted on
	top of the <literal>B1</literal> directory in the <literal>B</literal>
	file system, leading to this arrangement:</para>

	<mediaobject>
	<imageobject>
	<imagedata fileref="install/example-dir4" format="EPS">
	</imageobject>

	<textobject>
	<literallayout class="monospaced"> /
	\|
	+--- A1
	\|
	`--- A2
	\|
	+--- B1
	\| \|
	\| +--- C1
	\| \|
	\| `--- C2
	\|
	`--- B2</literallayout>
	</textobject>
	</mediaobject>

	<para>Or <literal>C</literal> could be mounted directly on to the
	<literal>A</literal> file system, under the <literal>A1</literal>
	directory:</para>

	<mediaobject>
	<imageobject>
	<imagedata fileref="install/example-dir5" format="EPS">
	</imageobject>

	<textobject>
	<literallayout class="monospaced"> /
	\|
	+--- A1
	\| \|
	\| +--- C1
	\| \|
	\| `--- C2
	\|
	`--- A2
	\|
	+--- B1
	\|
	`--- B2</literallayout>
	</textobject>
	</mediaobject>

	<para>If you are familiar with &ms-dos;, this is similar, although not
	identical, to the <command>join</command> command.</para>

	<para>This is not normally something you need to concern yourself with.
	Typically you create file systems when installing FreeBSD and decide
	where to mount them, and then never change them unless you add a new
	disk.</para>

	<para>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.</para>

	<itemizedlist>
	<title>Benefits of Multiple File Systems</title>

	<listitem>
	<para>Different file systems can have different <firstterm>mount
	options</firstterm>. 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 <filename>/home</filename>,
	from other file systems also allows them to be mounted
	<firstterm>nosuid</firstterm>; this option prevents the
	<firstterm>suid</firstterm>/<firstterm>guid</firstterm> bits on
	executables stored on the file system from taking effect, possibly
	improving security.</para>
	</listitem>

	<listitem>
	<para>FreeBSD 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.</para>
	</listitem>

	<listitem>
	<para>FreeBSD'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.</para>
	</listitem>
	</itemizedlist>

	<itemizedlist>
	<title>Benefit of a Single File System</title>

	<listitem>
	<para>File systems are a fixed size. If you create a file system when
	you install FreeBSD 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.</para>

	<important>
	<para>FreeBSD features the &man.growfs.8;
	command, which makes it possible to increase the size of
	file system on the fly, removing this limitation.</para>
	</important>
	</listitem>
	</itemizedlist>

	<para>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 <literal>a</literal> through to
	<literal>h</literal>. 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.</para>

	<para>FreeBSD also uses disk space for <firstterm>swap
	space</firstterm>. Swap space provides FreeBSD with
	<firstterm>virtual memory</firstterm>. 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 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.</para>

	<para>Some partitions have certain conventions associated with
	them.</para>

	<informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	<colspec colwidth="1*">
	<colspec colwidth="5*">

	<thead>
	<row>
	<entry>Partition</entry>

	<entry>Convention</entry>
	</row>
	</thead>

	<tbody valign="top">
	<row>
	<entry><literal>a</literal></entry>

	<entry>Normally contains the root file system</entry>
	</row>

	<row>
	<entry><literal>b</literal></entry>

	<entry>Normally contains swap space</entry>
	</row>

	<row>
	<entry><literal>c</literal></entry>

	<entry>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
	<literal>c</literal> partition. You would not normally create
	a file system on this partition.</entry>
	</row>

	<row>
	<entry><literal>d</literal></entry>

	<entry>Partition <literal>d</literal> used to have a special
	meaning associated with it, although that is now gone and
	<literal>d</literal> may work as any normal partition.</entry>
	</row>
	</tbody>
	</tgroup>
	</informaltable>

	<para>Each partition-that-contains-a-file-system is stored in what
	FreeBSD calls a <firstterm>slice</firstterm>. Slice is FreeBSD's term
	for what the common call partitions, and again, this is because of
	FreeBSD's &unix; background. Slices are numbered, starting at 1,
	through to 4.</para>

	<indexterm><primary>slices</primary></indexterm>
	<indexterm><primary>partitions</primary></indexterm>
	<indexterm><primary>dangerously dedicated</primary></indexterm>

	<para>Slice numbers follow
	the device name, prefixed with an <literal>s</literal>,
	starting at 1. So <quote>da0<emphasis>s1</emphasis></quote>
	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
	<quote>ad0<emphasis>s5</emphasis></quote> is the first
	extended slice on the first IDE disk. These devices are used by file
	systems that expect to occupy a slice.</para>

	<para>Slices, <quote>dangerously dedicated</quote> physical
	drives, and other drives contain
	<firstterm>partitions</firstterm>, which are represented as
	letters from <literal>a</literal> to <literal>h</literal>.
	This letter is appended to the device name, so
	<quote>da0<emphasis>a</emphasis></quote> is the a partition on
	the first da drive, which is <quote>dangerously dedicated</quote>.
	<quote>ad1s3<emphasis>e</emphasis></quote> is the fifth partition
	in the third slice of the second IDE disk drive.</para>

	<para>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
	<xref linkend="basics-dev-codes">.</para>

	<para>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, <literal>s</literal>, the slice number, and then the
	partition letter. Examples are shown in
	<xref linkend="basics-disk-slice-part">.</para>

	<para><xref linkend="basics-concept-disk-model"> shows a conceptual
	model of the disk layout that should help make things clearer.</para>

	<para>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.</para>

	<table frame="none" pgwide="1" id="basics-dev-codes">
	<title>Disk Device Codes</title>

	<tgroup cols="2">
	<colspec colwidth="1*">
	<colspec colwidth="5*">

	<thead>
	<row>
	<entry>Code</entry>

	<entry>Meaning</entry>
	</row>
	</thead>

	<tbody>
	<row>
	<entry><devicename>ad</devicename></entry>

	<entry>ATAPI (IDE) disk</entry>
	</row>

	<row>
	<entry><devicename>da</devicename></entry>

	<entry>SCSI direct access disk</entry>
	</row>

	<row>
	<entry><devicename>acd</devicename></entry>

	<entry>ATAPI (IDE) CDROM</entry>
	</row>

	<row>
	<entry><devicename>cd</devicename></entry>

	<entry>SCSI CDROM</entry>
	</row>

	<row>
	<entry><devicename>fd</devicename></entry>

	<entry>Floppy disk</entry>
	</row>
	</tbody>
	</tgroup>
	</table>

	<example id="basics-disk-slice-part">
	<title>Sample Disk, Slice, and Partition Names</title>

	<informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	<colspec colwidth="1*">
	<colspec colwidth="5*">

	<thead>
	<row>
	<entry>Name</entry>

	<entry>Meaning</entry>
	</row>
	</thead>

	<tbody>
	<row>
	<entry><literal>ad0s1a</literal></entry>

	<entry>The first partition (<literal>a</literal>) on the first
	slice (<literal>s1</literal>) on the first IDE disk
	(<literal>ad0</literal>).</entry>
	</row>

	<row>
	<entry><literal>da1s2e</literal></entry>

	<entry>The fifth partition (<literal>e</literal>) on the
	second slice (<literal>s2</literal>) on the second SCSI disk
	(<literal>da1</literal>).</entry>
	</row>
	</tbody>
	</tgroup>
	</informaltable>
	</example>

	<example id="basics-concept-disk-model">
	<title>Conceptual Model of a Disk</title>

	<para>This diagram shows FreeBSD'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, <devicename>C:</devicename>, and the second slice contains a
	FreeBSD installation. This example FreeBSD installation has three
	data partitions, and a swap partition.</para>

	<para>The three partitions will each hold a file system. Partition
	<literal>a</literal> will be used for the root file system,
	<literal>e</literal> for the <filename>/var</filename> directory
	hierarchy, and <literal>f</literal> for the
	<filename>/usr</filename> directory hierarchy.</para>

	<mediaobject>
	<imageobject>
	<imagedata fileref="install/disk-layout" format="EPS">
	</imageobject>

	<textobject>
	<literallayout class="monospaced">.-----------------. --.
	\| \| \|
	\| 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 \|
	: : \| \|
	\| \| \| \|
	\| \| --' \|
	`-----------------' --'</literallayout>
	</textobject>
	</mediaobject>
	</example>
	</sect1>



	<sect1 id="mount-unmount">
	<title>Mounting and Unmounting File Systems</title>

	<para>The file system is best visualized as a tree,
	rooted, as it were, at <filename>/</filename>.
	<filename>/dev</filename>, <filename>/usr</filename>, and the
	other directories in the root directory are branches, which may
	have their own branches, such as
	<filename>/usr/local</filename>, and so on.</para>

	<indexterm><primary>root file system</primary></indexterm>
	<para>There are various reasons to house some of these
	directories on separate file systems. <filename>/var</filename>
	contains the directories <filename>log/</filename>,
	<filename>spool/</filename>,
	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 <filename>/var</filename> from
	<filename>/</filename> is often favorable.</para>

	<para>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 <link
	linkend="network-nfs">Network File System</link> mounts, or CDROM
	drives.</para>

	<sect2 id="disks-fstab">
	<title>The <filename>fstab</filename> File</title>
	<indexterm>
	<primary>file systems</primary>
	<secondary>mounted with fstab</secondary>
	</indexterm>

	<para>During the <link linkend="boot">boot process</link>,
	file systems listed in <filename>/etc/fstab</filename> are
	automatically mounted (unless they are listed with the
	<option>noauto</option> option).</para>

	<para>The <filename>/etc/fstab</filename> file contains a list
	of lines of the following format:</para>

	<programlisting><replaceable>device</replaceable> <replaceable>/mount-point</replaceable> <replaceable>fstype</replaceable> <replaceable>options</replaceable> <replaceable>dumpfreq</replaceable> <replaceable>passno</replaceable></programlisting>

	<variablelist>
	<varlistentry>
	<term><literal>device</literal></term>
	<listitem>
	<para>A device name (which should exist), as explained in
	<xref linkend="disks-naming">.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>mount-point</literal></term>

	<listitem><para>A directory (which should exist), on which
	to mount the file system.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>fstype</literal></term>

	<listitem><para>The file system type to pass to
	&man.mount.8;. The default FreeBSD file system is
	<literal>ufs</literal>.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>options</literal></term>

	<listitem><para>Either <option>rw</option> for read-write
	file systems, or <option>ro</option> for read-only
	file systems, followed by any other options that may be
	needed. A common option is <option>noauto</option> for
	file systems not normally mounted during the boot sequence.
	Other options are listed in the &man.mount.8; manual page.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>dumpfreq</literal></term>

	<listitem><para>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.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><literal>passno</literal></term>

	<listitem>
	<para>This determines the order in which file systems should
	be checked. File systems that should be skipped should have
	their <literal>passno</literal> set to zero. The root
	file system (which needs to be checked before everything
	else) should have its <literal>passno</literal> set to
	one, and other file systems' <literal>passno</literal>
	should be set to values greater than one. If more than one
	file systems have the same <literal>passno</literal> then
	&man.fsck.8; will attempt to check file systems in parallel
	if possible.</para>
	</listitem>
	</varlistentry>
	</variablelist>

	<para>Consult the &man.fstab.5; manual page for more information
	on the format of the <filename>/etc/fstab</filename> file and
	the options it contains.</para>
	</sect2>

	<sect2 id="disks-mount">
	<title>The <command>mount</command> Command</title>
	<indexterm>
	<primary>file systems</primary>
	<secondary>mounting</secondary>
	</indexterm>

	<para>The &man.mount.8; command is what is ultimately used to
	mount file systems.</para>

	<para>In its most basic form, you use:</para>

	<informalexample>
	<screen>&prompt.root; <userinput>mount <replaceable>device</replaceable> <replaceable>mountpoint</replaceable></userinput></screen>
	</informalexample>

	<para>There are plenty of options, as mentioned in the
	&man.mount.8; manual page, but the most common are:</para>

	<variablelist>
	<title>Mount Options</title>

	<varlistentry>
	<term><option>-a</option></term>

	<listitem>
	<para>Mount all the file systems listed in
	<filename>/etc/fstab</filename>. Except those
	marked as <quote>noauto</quote>, excluded by the
	<option>-t</option> flag, or those that are already
	mounted.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><option>-d</option></term>

	<listitem>
	<para>Do everything except for the actual mount system call.
	This option is useful in conjunction with the
	<option>-v</option> flag to determine what
	&man.mount.8; is actually trying to do.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><option>-f</option></term>

	<listitem>
	<para>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.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><option>-r</option></term>

	<listitem>
	<para>Mount the file system read-only. This is identical
	to using the <option>ro</option> (<option>rdonly</option>
	for &os; versions older than 5.2) argument to the
	<option>-o</option> option.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><option>-t</option>
	<replaceable>fstype</replaceable></term>

	<listitem>
	<para>Mount the given file system as the given file system
	type, or mount only file systems of the given type, if
	given the <option>-a</option> option.</para>

	<para><quote>ufs</quote> is the default file system
	type.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><option>-u</option></term>

	<listitem>
	<para>Update mount options on the file system.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><option>-v</option></term>

	<listitem>
	<para>Be verbose.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><option>-w</option></term>

	<listitem>
	<para>Mount the file system read-write.</para>
	</listitem>
	</varlistentry>
	</variablelist>

	<para>The <option>-o</option> option takes a comma-separated list of
	the options, including the following:</para>

	<variablelist>
	<varlistentry>
	<term>noexec</term>

	<listitem>
	<para>Do not allow execution of binaries on this
	file system. This is also a useful security option.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term>nosuid</term>

	<listitem>
	<para>Do not interpret setuid or setgid flags on the
	file system. This is also a useful security option.</para>
	</listitem>
	</varlistentry>
	</variablelist>
	</sect2>

	<sect2 id="disks-umount">
	<title>The <command>umount</command> Command</title>
	<indexterm>
	<primary>file systems</primary>
	<secondary>unmounting</secondary>
	</indexterm>

	<para>The &man.umount.8; command takes, as a parameter, one of a
	mountpoint, a device name, or the <option>-a</option> or
	<option>-A</option> option.</para>

	<para>All forms take <option>-f</option> to force unmounting,
	and <option>-v</option> for verbosity. Be warned that
	<option>-f</option> is not generally a good idea. Forcibly
	unmounting file systems might crash the computer or damage data
	on the file system.</para>

	<para><option>-a</option> and <option>-A</option> are used to
	unmount all mounted file systems, possibly modified by the
	file system types listed after <option>-t</option>.
	<option>-A</option>, however, does not attempt to unmount the
	root file system.</para>
	</sect2>
	</sect1>

	<sect1 id="basics-processes">
	<title>Processes</title>

	<para>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 <firstterm>process</firstterm>.
	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.</para>

	<para>Each process is uniquely identified by a number called a
	<firstterm>process ID</firstterm>, or <firstterm>PID</firstterm>, 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;. <command>init</command> is always the first
	process, so its PID is always 1. <command>init</command> is started
	automatically by the kernel when FreeBSD starts.</para>

	<para>Two commands are particularly useful to see the processes on the
	system, &man.ps.1; and &man.top.1;. The <command>ps</command> 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 <command>top</command> command displays all the
	running processes, and updates the display every few seconds, so that
	you can interactively see what your computer is doing.</para>

	<para>By default, <command>ps</command> only shows you the commands that are running
	and are owned by you. For example:</para>

	<screen>&prompt.user; <userinput>ps</userinput>
	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</screen>

	<para>As you can see in this example, the output from &man.ps.1; is
	organized into a number of columns. <literal>PID</literal> 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 <literal>TT</literal> column shows the tty the program is running on, and can
	safely be ignored for the moment. <literal>STAT</literal> shows the
	program's state, and again, can be safely ignored.
	<literal>TIME</literal> 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 most programs spend a lot of time waiting
	for things to happen before they need to spend time on the CPU.
	Finally, <literal>COMMAND</literal> is the command line that was used to
	run the program.</para>

	<para>&man.ps.1; supports a number of different options to change the
	information that is displayed. One of the most useful sets is
	<literal>auxww</literal>. <option>a</option> displays information
	about all the running processes, not just your own. <option>u</option>
	displays the username of the process' owner, as well as memory usage.
	<option>x</option> displays information about daemon processes, and
	<option>ww</option> 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.</para>

	<para>The output from &man.top.1; is similar. A sample session looks like
	this:</para>

	<screen>&prompt.user; <userinput>top</userinput>
	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
	...</screen>

	<para>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.</para>

	<para>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 <application>&netscape;</application> has
	required almost 30 MB of RAM, but is currently only using 9 MB.</para>

	<para>&man.top.1; automatically updates this display every two seconds;
	this can be changed with the <option>s</option> option.</para>
	</sect1>

	<sect1 id="basics-daemons">
	<title>Daemons, Signals, and Killing Processes</title>

	<para>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
	<firstterm>terminal</firstterm>. 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.</para>

	<para>We call these programs <firstterm>daemons</firstterm>. 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.</para>

	<para>There is a convention to name programs that normally run as daemons
	with a trailing <quote>d</quote>. <application>BIND</application> is the
	Berkeley Internet Name Domain, but the actual program that executes is called
	<command>named</command>; the <application>Apache</application> web
	server program is called <command>httpd</command>; the line printer
	spooling daemon is <command>lpd</command> and so on. This is a
	convention, not a hard and fast rule; for example, the main mail daemon
	for the <application>Sendmail</application> application is called
	<command>sendmail</command>, and not <command>maild</command>, as you
	might imagine.</para>

	<para>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 <firstterm>signal</firstterm>.
	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
	<username>root</username> user, who can send signals to everyone's
	processes.</para>

	<para>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 <firstterm>Segmentation
	Violation</firstterm> signal (<literal>SIGSEGV</literal>). 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
	(<literal>SIGALRM</literal>), and so on.</para>

	<para>Two signals can be used to stop a process,
	<literal>SIGTERM</literal> and <literal>SIGKILL</literal>.
	<literal>SIGTERM</literal> is the polite way to kill a process; the
	process can <emphasis>catch</emphasis> 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 <literal>SIGTERM</literal> if it is in
	the middle of some task that can not be interrupted.</para>

	<para><literal>SIGKILL</literal> can not be ignored by a process. This is
	the <quote>I do not care what you are doing, stop right now</quote>
	signal. If you send <literal>SIGKILL</literal> to a process then
	FreeBSD will stop that process there and then<footnote>
	<para>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
	<quote>uninterruptible</quote>. Eventually the process will time
	out, typically after two minutes. As soon as this time out occurs
	the process will be killed.</para>
	</footnote>.</para>

	<para>The other signals you might want to use are
	<literal>SIGHUP</literal>, <literal>SIGUSR1</literal>, and
	<literal>SIGUSR2</literal>. These are general purpose signals, and
	different applications will do different things when they are
	sent.</para>

	<para>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 <command>httpd</command>, 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
	<literal>SIGHUP</literal> signal by re-reading their configuration
	file. So instead of killing and restarting <command>httpd</command> you
	would send it the <literal>SIGHUP</literal> 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.</para>

	<para>Signals are sent using the &man.kill.1; command, as this example
	shows.</para>

	<procedure>
	<title>Sending a Signal to a Process</title>

	<para>This example shows how to send a signal to &man.inetd.8;. The
	<command>inetd</command> configuration file is
	<filename>/etc/inetd.conf</filename>, and <command>inetd</command> will re-read
	this configuration file when it is sent
	<literal>SIGHUP</literal>.</para>

	<step>
	<para>Find the process ID of the process you want to send the signal
	to. Do this using &man.ps.1; and &man.grep.1;. The &man.grep.1;
	command is used to search through output, looking for the string you
	specify. This command is run as a normal user, and &man.inetd.8; is
	run as <username>root</username>, so the <option>ax</option> options
	must be given to &man.ps.1;.</para>

	<screen>&prompt.user; <userinput>ps -ax \| grep inetd</userinput>
	198 ?? IWs 0:00.00 inetd -wW</screen>

	<para>So the &man.inetd.8; PID is 198. In some cases the
	<literal>grep inetd</literal> command might also appear in this
	output. This is because of the way &man.ps.1; has to find the list
	of running processes.</para>
	</step>

	<step>
	<para>Use &man.kill.1; to send the signal. Because &man.inetd.8; is
	being run by <username>root</username> you must use &man.su.1; to
	become <username>root</username> first.</para>

	<screen>&prompt.user; <userinput>su</userinput>
	<prompt>Password:</prompt>
	&prompt.root; <userinput>/bin/kill -s HUP 198</userinput></screen>

	<para>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 <errorname>kill:
	<replaceable>PID</replaceable>: Operation not
	permitted</errorname>. 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 <errorname>kill:
	<replaceable>PID</replaceable>: No such process</errorname>.</para>

	<note>
	<title>Why Use <command>/bin/kill</command>?</title>

	<para>Many shells provide the <command>kill</command> command as a
	built in command; that is, the shell will send the signal
	directly, rather than running <filename>/bin/kill</filename>.
	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
	<command>/bin/kill <replaceable>...</replaceable></command>
	command directly.</para>
	</note>
	</step>
	</procedure>

	<para>Sending other signals is very similar, just substitute
	<literal>TERM</literal> or <literal>KILL</literal> in the command line
	as necessary.</para>

	<important>
	<para>Killing random process on the system can be a bad idea. In
	particular, &man.init.8;, process ID 1, is very special. Running
	<command>/bin/kill -s KILL 1</command> is a quick way to shutdown your
	system. <emphasis>Always</emphasis> double check the arguments you
	run &man.kill.1; with <emphasis>before</emphasis> you press
	<keycap>Return</keycap>.</para>
	</important>
	</sect1>

	<sect1 id="shells">
	<title>Shells</title>
	<indexterm><primary>shells</primary></indexterm>
	<indexterm><primary>command line</primary></indexterm>

	<para>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
	<command>sh</command>, the Bourne Shell, and <command>tcsh</command>,
	the improved C-shell. Many other shells are available
	from the FreeBSD Ports Collection, such as
	<command>zsh</command> and <command>bash</command>.</para>

	<para>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 <command>tcsh</command>. If you have come from Linux or are new
	to a &unix; command line interface you might try <command>bash</command>.
	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.</para>

	<para>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 <keycap>Tab</keycap> key on the keyboard. Here is
	an example. Suppose you have two files called
	<filename>foobar</filename> and <filename>foo.bar</filename>. You
	want to delete <filename>foo.bar</filename>. So what you would type
	on the keyboard is: <command>rm fo[<keycap>Tab</keycap>].[<keycap>Tab</keycap>]</command>.</para>

	<para>The shell would print out <command>rm
	foo[BEEP].bar</command>.</para>

	<para>The [BEEP] is the console bell, which is the shell telling me it
	was unable to totally complete the filename because there is more
	than one match. Both <filename>foobar</filename> and
	<filename>foo.bar</filename> start with <literal>fo</literal>, but
	it was able to complete to <literal>foo</literal>. If you type in
	<literal>.</literal>, then hit <keycap>Tab</keycap> again, the shell would be able to
	fill in the rest of the filename for you.</para>
	<indexterm><primary>environment variables</primary></indexterm>

	<para>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 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:</para>
	<indexterm><primary>environment variables</primary></indexterm>

	<informaltable frame="none" pgwide="1">
	<tgroup cols="2">
	<thead>
	<row>
	<entry>Variable</entry>
	<entry>Description</entry>
	</row>
	</thead>

	<tbody>
	<row>
	<entry><envar>USER</envar></entry>
	<entry>Current logged in user's name.</entry>
	</row>

	<row>
	<entry><envar>PATH</envar></entry>
	<entry>Colon-separated list of directories to search for
	binaries.</entry>
	</row>

	<row>
	<entry><envar>DISPLAY</envar></entry>
	<entry>Network name of the X11 display to connect to, if
	available.</entry>
	</row>

	<row>
	<entry><envar>SHELL</envar></entry>
	<entry>The current shell.</entry>
	</row>

	<row>
	<entry><envar>TERM</envar></entry>
	<entry>The name of the user's type of terminal. Used to determine the
	capabilities of the terminal.</entry>
	</row>

	<row>
	<entry><envar>TERMCAP</envar></entry>
	<entry>Database entry of the terminal escape codes to perform
	various terminal functions.</entry>
	</row>

	<row>
	<entry><envar>OSTYPE</envar></entry>
	<entry>Type of operating system. e.g., FreeBSD.</entry>
	</row>

	<row>
	<entry><envar>MACHTYPE</envar></entry>
	<entry>The CPU architecture that the system is running
	on.</entry>
	</row>

	<row>
	<entry><envar>EDITOR</envar></entry>
	<entry>The user's preferred text editor.</entry>
	</row>

	<row>
	<entry><envar>PAGER</envar></entry>
	<entry>The user's preferred text pager.</entry>
	</row>

	<row>
	<entry><envar>MANPATH</envar></entry>
	<entry>Colon-separated list of directories to search for
	manual pages.</entry>
	</row>
	</tbody>
	</tgroup>
	</informaltable>

	<indexterm><primary>Bourne shells</primary></indexterm>
	<para>Setting an environment variable differs somewhat from
	shell to shell. For example, in the C-Style shells such as
	<command>tcsh</command> and <command>csh</command>, you would use
	<command>setenv</command> to set environment variables.
	Under Bourne shells such as <command>sh</command> and
	<command>bash</command>, you would use
	<command>export</command> to set your current environment
	variables. For example, to set or modify the
	<envar>EDITOR</envar> environment variable, under <command>csh</command> or
	<command>tcsh</command> a
	command like this would set <envar>EDITOR</envar> to
	<filename>/usr/local/bin/emacs</filename>:</para>

	<screen>&prompt.user; <userinput>setenv EDITOR /usr/local/bin/emacs</userinput></screen>

	<para>Under Bourne shells:</para>

	<screen>&prompt.user; <userinput>export EDITOR="/usr/local/bin/emacs"</userinput></screen>

	<para>You can also make most shells expand the environment variable by
	placing a <literal>$</literal> character in front of it on the
	command line. For example, <command>echo $TERM</command> would
	print out whatever <envar>$TERM</envar> is set to, because the shell
	expands <envar>$TERM</envar> and passes it on to <command>echo</command>.</para>

	<para>Shells treat a lot of special characters, called meta-characters
	as special representations of data. The most common one is the
	<literal>*</literal> 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
	<command>echo *</command> is almost the same as typing in
	<command>ls</command> because the shell takes all the files that
	match <literal>*</literal> and puts them on the command line for
	<command>echo</command> to see.</para>

	<para>To prevent the shell from interpreting these special characters,
	they can be escaped from the shell by putting a backslash
	(<literal>\</literal>) character in front of them. <command>echo
	$TERM</command> prints whatever your terminal is set to.
	<command>echo \$TERM</command> prints <envar>$TERM</envar> as
	is.</para>

	<sect2 id="changing-shells">
	<title>Changing Your Shell</title>

	<para>The easiest way to change your shell is to use the
	<command>chsh</command> command. Running <command>chsh</command> will
	place you into the editor that is in your <envar>EDITOR</envar>
	environment variable; if it is not set, you will be placed in
	<command>vi</command>. Change the <quote>Shell:</quote> line
	accordingly.</para>

	<para>You can also give <command>chsh</command> the
	<option>-s</option> 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 <command>bash</command>, the following should do the
	trick:</para>

	<screen>&prompt.user; <userinput>chsh -s /usr/local/bin/bash</userinput></screen>

	<note>
	<para>The shell that you wish to use <emphasis>must</emphasis> be
	present in the <filename>/etc/shells</filename> file. If you
	have installed a shell from the <link linkend="ports">ports
	collection</link>, then this should have been done for you
	already. If you installed the shell by hand, you must do
	this.</para>

	<para>For example, if you installed <command>bash</command> by hand
	and placed it into <filename>/usr/local/bin</filename>, you would
	want to:</para>

	<screen>&prompt.root; <userinput>echo "/usr/local/bin/bash" >> /etc/shells</userinput></screen>

	<para>Then rerun <command>chsh</command>.</para>
	</note>
	</sect2>
	</sect1>

	<sect1 id="editors">
	<title>Text Editors</title>
	<indexterm><primary>text editors</primary></indexterm>
	<indexterm><primary>editors</primary></indexterm>

	<para>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.</para>

	<indexterm>
	<primary><command>ee</command></primary>
	</indexterm>
	<indexterm>
	<primary>editors</primary>
	<secondary><command>ee</command></secondary>
	</indexterm>
	<para>The easiest and simplest editor to learn is an editor called
	<application>ee</application>, which stands for easy editor. To
	start <application>ee</application>, one would type at the command
	line <command>ee <replaceable>filename</replaceable></command> where
	<replaceable>filename</replaceable> is the name of the file to be edited.
	For example, to edit <filename>/etc/rc.conf</filename>, type in
	<command>ee /etc/rc.conf</command>. Once inside of
	<command>ee</command>, all of the
	commands for manipulating the editor's functions are listed at the
	top of the display. The caret <literal>^</literal> character represents
	the <keycap>Ctrl</keycap> key on the keyboard, so <literal>^e</literal> expands to the key combination
	<keycombo action="simul"><keycap>Ctrl</keycap><keycap>e</keycap></keycombo>. To leave
	<application>ee</application>, hit the <keycap>Esc</keycap> key, then choose leave
	editor. The editor will prompt you to save any changes if the file
	has been modified.</para>

	<indexterm>
	<primary><command>vi</command></primary>
	</indexterm>
	<indexterm>
	<primary>editors</primary>
	<secondary><command>vi</command></secondary>
	</indexterm>
	<indexterm>
	<primary><command>emacs</command></primary>
	</indexterm>
	<indexterm>
	<primary>editors</primary>
	<secondary><command>emacs</command></secondary>
	</indexterm>
	<para>FreeBSD also comes with more powerful text editors such as
	<application>vi</application> as part of the base system, while other editors, like
	<application>Emacs</application> and <application>vim</application>,
	are part of the FreeBSD Ports Collection (<filename role="package">editors/emacs</filename> and <filename role="package">editors/vim</filename>). 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
	<application>vim</application> or <application>Emacs</application>
	will save you much more time in the long run.</para>

	<para>Many applications which modify files or require typed input
	will automatically open a text editor. To alter the default
	editor used, set the <envar>EDITOR</envar> environment
	variable. See <link linkend="shells">shells</link>
	section for more details.</para>
	</sect1>

	<sect1 id="basics-devices">
	<title>Devices and Device Nodes</title>

	<para>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
	<filename>/var/run/dmesg.boot</filename>.</para>

	<para>For example, <devicename>acd0</devicename> is the
	first IDE CDROM drive, while <devicename>kbd0</devicename>
	represents the keyboard.</para>

	<para>Most of these devices in a &unix; operating system must be
	accessed through special files called device nodes, which are
	located in the <filename>/dev</filename> directory.</para>

	<sect2>
	<title>Creating Device Nodes</title>
	<para>When adding a new device to your system, or compiling
	in support for additional devices, new device nodes must
	be created.</para>

	<sect3>
	<title><literal>DEVFS</literal> (DEVice File System)</title>

	<para> The device file system, or <literal>DEVFS</literal>, provides access to
	kernel's device namespace in the global file system namespace.
	Instead of having to create and modify device nodes,
	<literal>DEVFS</literal> maintains this particular file system for you.</para>

	<para>See the &man.devfs.5; manual page for more
	information.</para>
	</sect3>
	</sect2>
	</sect1>

	<sect1 id="binary-formats">
	<title>Binary Formats</title>

	<para>To understand why &os; uses the &man.elf.5;
	format, you must first know a little about the three currently
	<quote>dominant</quote> executable formats for &unix;:</para>

	<itemizedlist>
	<listitem>
	<para>&man.a.out.5;</para>

	<para>The oldest and <quote>classic</quote> &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.</para>
	</listitem>

	<listitem>
	<para><acronym>COFF</acronym></para>

	<para>The SVR3 object format. The header now comprises a
	section table, so you can have more than just .text, .data,
	and .bss sections.</para>
	</listitem>

	<listitem>
	<para>&man.elf.5;</para>

	<para>The successor to <acronym>COFF</acronym>, featuring
	multiple sections and 32-bit or 64-bit possible values. One
	major drawback: <acronym>ELF</acronym> was also 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
	true.</para>

	<para>FreeBSD tries to work around this problem somewhat by
	providing a utility for <emphasis>branding</emphasis> a
	known <acronym>ELF</acronym> executable with information
	about the ABI it is compliant with. See the manual page for
	&man.brandelf.1; for more information.</para>
	</listitem>
	</itemizedlist>

	<para>FreeBSD comes from the <quote>classic</quote> 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
	<acronym>ELF</acronym> binaries (and kernels) on a FreeBSD
	system for some time before that, FreeBSD initially resisted the
	<quote>push</quote> to switch to <acronym>ELF</acronym> as the
	default format. Why? Well, when the Linux camp made their
	painful transition to <acronym>ELF</acronym>, it was not so much
	to flee the <filename>a.out</filename> 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
	<acronym>ELF</acronym> tools available offered a solution to the
	shared library problem and were generally seen as <quote>the way
	forward</quote> 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.</para>

	<para>So, why are there so many different formats?</para>

	<para>Back in the dim, dark past, there was simple hardware. This
	simple hardware supported a simple, small system. <filename>a.out</filename> 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 <filename>a.out</filename> format because it was sufficient
	for the early ports of &unix; to architectures like the Motorola
	68k, VAXen, etc.</para>

	<para>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 <acronym>RISC</acronym>), <filename>a.out</filename>
	was ill-suited for this hardware, so many formats were developed
	to get to a better performance from this hardware than the
	limited, simple <filename>a.out</filename> format could
	offer. Things like <acronym>COFF</acronym>,
	<acronym>ECOFF</acronym>, and a few obscure others were invented
	and their limitations explored before things seemed to settle on
	<acronym>ELF</acronym>.</para>

	<para>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 <filename>a.out</filename> 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 <filename>a.out</filename> format to
	allow all of these things to happen, and they basically worked
	for a time. In time, <filename>a.out</filename> was not up to
	handling all these problems without an ever increasing overhead
	in code and complexity. While <acronym>ELF</acronym> solved many
	of these problems, it would be painful to switch from the system
	that basically worked. So <acronym>ELF</acronym> had to wait
	until it was more painful to remain with
	<filename>a.out</filename> than it was to migrate to
	<acronym>ELF</acronym>.</para>

	<para>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 <application>as</application> and <application>ld</application> were not up to the
	task. The new GNU tools chain (<application>binutils</application>) does support cross
	compiling, <acronym>ELF</acronym>, shared libraries, C++
	extensions, etc. In addition, many vendors are releasing
	<acronym>ELF</acronym> binaries, and it is a good thing for
	FreeBSD to run them.</para>

	<para><acronym>ELF</acronym> is more expressive than <filename>a.out</filename> and
	allows more extensibility in the base system. The
	<acronym>ELF</acronym> tools are better maintained, and offer
	cross compilation support, which is important to many people.
	<acronym>ELF</acronym> may be a little slower than <filename>a.out</filename>, 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
	<filename>a.out</filename> will be moved out of the <filename>GENERIC</filename>
	kernel, and eventually removed from the kernel once the need to
	run legacy <filename>a.out</filename> programs is past.</para>
	</sect1>

	<sect1 id="basics-more-information">
	<title>For More Information</title>

	<sect2 id="basics-man">
	<title>Manual Pages</title>
	<indexterm><primary>manual pages</primary></indexterm>

	<para>The most comprehensive documentation on FreeBSD 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 <command>man</command> command. Use
	of the <command>man</command> command is simple:</para>

	<screen>&prompt.user; <userinput>man <replaceable>command</replaceable></userinput></screen>

	<para><literal>command</literal> is the name of the command you
	wish to learn about. For example, to learn more about
	<command>ls</command> command type:</para>

	<screen>&prompt.user; <userinput>man ls</userinput></screen>

	<para>The online manual is divided up into numbered sections:</para>

	<orderedlist>
	<listitem>
	<para>User commands.</para>
	</listitem>

	<listitem>
	<para>System calls and error numbers.</para>
	</listitem>

	<listitem>
	<para>Functions in the C libraries.</para>
	</listitem>

	<listitem>
	<para>Device drivers.</para>
	</listitem>

	<listitem>
	<para>File formats.</para>
	</listitem>

	<listitem>
	<para>Games and other diversions.</para>
	</listitem>

	<listitem>
	<para>Miscellaneous information.</para>
	</listitem>

	<listitem>
	<para>System maintenance and operation commands.</para>
	</listitem>

	<listitem>
	<para>Kernel developers.</para>
	</listitem>
	</orderedlist>

	<para>In some cases, the same topic may appear in more than one
	section of the online manual. For example, there is a
	<command>chmod</command> user command and a
	<function>chmod()</function> system call. In this case, you can
	tell the <command>man</command> command which one you want by specifying the
	section:</para>

	<screen>&prompt.user; <userinput>man 1 chmod</userinput></screen>

	<para>This will display the manual page for the user command
	<command>chmod</command>. References to a particular section of
	the online manual are traditionally placed in parenthesis in
	written documentation, so &man.chmod.1; refers to the
	<command>chmod</command> user command and &man.chmod.2; refers to
	the system call.</para>

	<para>This is fine if you know the name of the command and simply
	wish to know how to use it, but what if you cannot recall the
	command name? You can use <command>man</command> to search for keywords in the
	command descriptions by using the <option>-k</option>
	switch:</para>

	<screen>&prompt.user; <userinput>man -k mail</userinput></screen>

	<para>With this command you will be presented with a list of
	commands that have the keyword <quote>mail</quote> in their
	descriptions. This is actually functionally equivalent to using
	the <command>apropos</command> command.</para>

	<para>So, you are looking at all those fancy commands in
	<filename>/usr/bin</filename> but do not have the faintest idea
	what most of them actually do? Simply do:</para>

	<screen>&prompt.user; <userinput>cd /usr/bin</userinput>
	&prompt.user; <userinput>man -f *</userinput></screen>

	<para>or</para>

	<screen>&prompt.user; <userinput>cd /usr/bin</userinput>
	&prompt.user; <userinput>whatis *</userinput></screen>

	<para>which does the same thing.</para>
	</sect2>

	<sect2 id="basics-info">
	<title>GNU Info Files</title>
	<indexterm><primary>Free Software Foundation</primary></indexterm>

	<para>FreeBSD 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
	<literal>info</literal> files which can be viewed with the
	<command>info</command> command or, if you installed
	<application>emacs</application>, the info mode of
	<application>emacs</application>.</para>

	<para>To use the &man.info.1; command, simply type:</para>

	<screen>&prompt.user; <userinput>info</userinput></screen>

	<para>For a brief introduction, type <literal>h</literal>. For a
	quick command reference, type <literal>?</literal>.</para>
	</sect2>
	</sect1>
	</chapter>
	<!--
	Local Variables:
	mode: sgml
	sgml-declaration: "../chapter.decl"
	sgml-indent-data: t
	sgml-omittag: nil
	sgml-always-quote-attributes: t
	sgml-parent-document: ("../book.sgml" "part" "chapter")
	End:
	-->

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