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Move section on mounting and unmounting filesystems from

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Storage chapter to Basics.

Suggested by: nik and murray
This commit is contained in:
Chern Lee 2001-09-13 00:05:59 +00:00
parent d7a17bf2f2
commit 6cfc9d250f
Notes: svn2git 2020-12-08 03:00:23 +00:00 
svn path=/head/; revision=10674
1 changed files with 255 additions and 1 deletions

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en_US.ISO8859-1/books/handbook/basics/chapter.sgml
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<!--
The FreeBSD Documentation Project
$FreeBSD: doc/en_US.ISO8859-1/books/handbook/basics/chapter.sgml,v 1.44 2001/08/30 22:44:35 logo Exp $
$FreeBSD: doc/en_US.ISO8859-1/books/handbook/basics/chapter.sgml,v 1.45 2001/09/08 00:12:38 murray Exp $
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<chapter id="basics">
@ -449,6 +449,260 @@
</sect1>
<sect1 id="mount-unmount">
<title>Mounting and Unmounting Filesystems</title>
<para>The filesystem 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 filesystem</primary></indexterm>
<para>There are various reasons to house some of these
directories on separate filesystems. <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 filesystem
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 filesystems is if they are to be housed on separate
physical disks, or are separate virtual disks, such as <link
linkend="nfs">Network File System</link> mounts, or CDROM
drives.</para>
<sect2 id="disks-fstab">
<title>The <filename>fstab</filename> File</title>
<indexterm>
<primary>filesystems</primary>
<secondary>mounted with fstab</secondary>
</indexterm>
<para>During the <link linkend="boot">boot process</link>,
filesystems 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
<link linkend="disks-naming">Disk naming
conventions</link> above.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>mount-point</literal></term>
<listitem><para>A directory (which should exist), on which
to mount the filesystem.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>fstype</literal></term>
<listitem><para>The filesystem type to pass to
&man.mount.8;. The default FreeBSD filesystem is
<literal>ufs</literal>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>options</literal></term>
<listitem><para>Either <option>rw</option> for read-write
filesystems, or <option>ro</option> for read-only
filesystems, followed by any other options that may be
needed. A common option is <option>noauto</option> for
filesystems 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>The number of days the filesystem should be
dumped, and <literal>passno</literal> is the pass number
during which the filesystem is checked during the boot
sequence.</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2 id="disks-mount">
<title>The mount Command</title>
<indexterm>
<primary>filesystems</primary>
<secondary>mounting</secondary>
</indexterm>
<para>The &man.mount.8; command is what is ultimately used to
mount filesystems.</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 filesystems listed in
<filename>/etc/fstab</filename>. Exceptions are 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 system call.
This option is useful in conjunction with the
<option>-v</option> flag to determine what the
<command>mount</command> is actually trying to do.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-f</option></term>
<listitem>
<para>Force the mount of an unclean filesystem
(dangerous), or forces the revocation of write access
when downgrading a filesystem's mount status from
read-write to read-only.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-r</option></term>
<listitem>
<para>Mount the filesystem read-only. This is identical
to using the <option>rdonly</option> argument to the
<option>-o</option> option.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-t</option>
<replaceable>fstype</replaceable></term>
<listitem>
<para>Mount the given filesystem as the given filesystem
type, or mount only filesystems of the given type, if
given the <option>-a</option> option.</para>
<para><quote>ufs</quote> is the default filesystem
type.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-u</option></term>
<listitem>
<para>Update mount options on the filesystem.</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 filesystem 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>nodev</term>
<listitem>
<para>Do not interpret special devices on the
filesystem. This is a useful security option.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>noexec</term>
<listitem>
<para>Do not allow execution of binaries on this
filesystem. 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
filesystem. 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>filesystems</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.</para>
<para><option>-a</option> and <option>-A</option> are used to
unmount all mounted filesystems, possibly modified by the
filesystem types listed after <option>-t</option>.
<option>-A</option>, however, does not attempt to unmount the
root filesystem.</para>
</sect2>
</sect1>
<sect1 id="basics-processes">
<title>Processes</title>