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systemd/man/systemd.swap.xml
Tom Gundersen 12b42c7667 man: revert dynamic paths for split-usr setups
This did not really work out as we had hoped. Trying to do this upstream
introduced several problems that probably makes it better suited as a
downstream patch after all. At any rate, it is not releaseable in the
current state, so we at least need to revert this before the release.

 * by adjusting the path to binaries, but not do the same thing to the
   search path we end up with inconsistent man-pages. Adjusting the search
   path too would be quite messy, and it is not at all obvious that this is
   worth the effort, but at any rate it would have to be done before we
   could ship this.

 * this means that distributed man-pages does not make sense as they depend
   on config options, and for better or worse we are still distributing
   man pages, so that is something that definitely needs sorting out before
   we could ship with this patch.

 * we have long held that split-usr is only minimally supported in order
   to boot, and something we hope will eventually go away. So before we start
   adding even more magic/effort in order to make this work nicely, we should
   probably question if it makes sense at all.
2015-06-18 19:47:44 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id="systemd.swap">
<refentryinfo>
<title>systemd.swap</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.swap</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.swap</refname>
<refpurpose>Swap unit configuration</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename><replaceable>swap</replaceable>.swap</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>A unit configuration file whose name ends in
<literal>.swap</literal> encodes information about a swap device
or file for memory paging controlled and supervised by
systemd.</para>
<para>This man page lists the configuration options specific to
this unit type. See
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for the common options of all unit configuration files. The common
configuration items are configured in the generic [Unit] and
[Install] sections. The swap specific configuration options are
configured in the [Swap] section.</para>
<para>Additional options are listed in
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
which define the execution environment the
<citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
binary is executed in, and in
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
which define the way the processes are terminated, and in
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
which configure resource control settings for the processes of the
service.</para>
<para>Swap units must be named after the devices
or files they control. Example: the swap device
<filename noindex='true'>/dev/sda5</filename> must be configured in a
unit file <filename>dev-sda5.swap</filename>. For details about
the escaping logic used to convert a file system path to a unit
name, see
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
<para>All swap units automatically get the appropriate
dependencies on the devices or on the mount points of the files
they are activated from.</para>
<para>Swap units with <varname>DefaultDependencies=</varname>
enabled implicitly acquire a conflicting dependency to
<filename>umount.target</filename> so that they are deactivated at
shutdown.</para>
</refsect1>
<refsect1>
<title><filename>fstab</filename></title>
<para>Swap units may either be configured via unit files, or via
<filename>/etc/fstab</filename> (see
<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details). Swaps listed in <filename>/etc/fstab</filename> will
be converted into native units dynamically at boot and when the
configuration of the system manager is reloaded. See
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for details about the conversion.</para>
<para>If a swap device or file is configured in both
<filename>/etc/fstab</filename> and a unit file, the configuration
in the latter takes precedence.</para>
<para>When reading <filename>/etc/fstab</filename> a few special
options are understood by systemd which influence how dependencies
are created for swap units.</para>
<variablelist class='fstab-options'>
<varlistentry>
<term><option>noauto</option></term>
<term><option>auto</option></term>
<listitem><para>With <option>noauto</option> the swap unit
will not be added as a dependency for
<filename>swap.target</filename>. This means that it will not
be activated automatically during boot, unless it is pulled in
by some other unit. Option <option>auto</option> has the
opposite meaning and is the default.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>nofail</option></term>
<listitem><para>With <option>nofail</option> the swap unit
will be only wanted, not required by
<filename>swap.target</filename>. This means that the boot
will continue even if this swap device is not activated
successfully.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Options</title>
<para>Swap files must include a [Swap] section, which carries
information about the swap device it supervises. A number of
options that may be used in this section are shared with other
unit types. These options are documented in
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
The options specific to the [Swap] section of swap units are the
following:</para>
<variablelist class='unit-directives'>
<varlistentry>
<term><varname>What=</varname></term>
<listitem><para>Takes an absolute path of a device node or
file to use for paging. See
<citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for details. If this refers to a device node, a dependency on
the respective device unit is automatically created. (See
<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for more information.) If this refers to a file, a dependency
on the respective mount unit is automatically created. (See
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for more information.) This option is
mandatory.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Priority=</varname></term>
<listitem><para>Swap priority to use when activating the swap
device or file. This takes an integer. This setting is
optional and ignored when priority is set by <option>pri=</option> in the
<varname>Options=</varname> option.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>Options=</varname></term>
<listitem><para>May contain an option string for the swap
device. This may be used for controlling discard options among
other functionality, if the swap backing device supports the
discard or trim operation. (See
<citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for more information.) </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>TimeoutSec=</varname></term>
<listitem><para>Configures the time to wait for the swapon
command to finish. If a command does not exit within the
configured time, the swap will be considered failed and be
shut down again. All commands still running will be terminated
forcibly via <constant>SIGTERM</constant>, and after another
delay of this time with <constant>SIGKILL</constant>. (See
<option>KillMode=</option> in
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
Takes a unit-less value in seconds, or a time span value such
as "5min 20s". Pass <literal>0</literal> to disable the
timeout logic. Defaults to
<varname>DefaultTimeoutStartSec=</varname> from the manager
configuration file (see
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
</para></listitem>
</varlistentry>
</variablelist>
<para>Check
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for more settings.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>