man/systemd.swap.xml

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  24
  25 <refentry id="systemd.swap">
  26         <refentryinfo>
  27                 <title>systemd.swap</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.swap</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.swap</refname>
  47                 <refpurpose>Swap unit configuration</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename><replaceable>swap</replaceable>.swap</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para>A unit configuration file whose name ends in
  58                 <literal>.swap</literal> encodes information about a
  59                 swap device or file for memory paging controlled and
  60                 supervised by systemd.</para>
  61
  62                 <para>This man page lists the configuration options
  63                 specific to this unit type. See
  64                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  65                 for the common options of all unit configuration
  66                 files. The common configuration items are configured
  67                 in the generic [Unit] and [Install] sections. The swap
  68                 specific configuration options are configured in the
  69                 [Swap] section.</para>
  70
  71                 <para>Additional options are listed in
  72                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  73                 which define the execution environment the
  74                 <citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  75                 binary is executed in, and in
  76                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  77                 which define the way the processes are
  78                 terminated.</para>
  79
  80                 <para>Swap units must be named after the devices
  81                 or files they control. Example: the swap device
  82                 <filename noindex='true'>/dev/sda5</filename> must be configured in a
  83                 unit file <filename>dev-sda5.swap</filename>. For
  84                 details about the escaping logic used to convert a
  85                 file system path to a unit name see
  86                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
  87
  88                 <para>All swap units automatically get the appropriate
  89                 dependencies on the devices or on the mount points
  90                 of the files they are activated from.</para>
  91
  92                 <para>Swap units with
  93                 <varname>DefaultDependencies=</varname> enabled
  94                 implicitly acquire a conflicting dependency to
  95                 <filename>umount.target</filename> so that they are
  96                 deactivated at shutdown.</para>
  97         </refsect1>
  98
  99         <refsect1>
 100                 <title><filename>fstab</filename></title>
 101
 102                 <para>Swap units may either be configured via unit
 103                 files, or via <filename>/etc/fstab</filename> (see
 104                 <citerefentry><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 105                 for details). Swaps listed in
 106                 <filename>/etc/fstab</filename> will be converted into
 107                 native units dynamically at boot and when the
 108                 configuration of the system manager is
 109                 reloaded. See
 110                 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 111                 for details about the conversion.</para>
 112
 113                 <para>If a swap device or file is configured in both
 114                 <filename>/etc/fstab</filename> and a unit file the
 115                 configuration in the latter takes precedence.</para>
 116
 117                 <para>Unless the <option>noauto</option> option is set
 118                 for them all swap units configured in
 119                 <filename>/etc/fstab</filename> are also added as
 120                 requirements to <filename>swap.target</filename>, so
 121                 that they are waited for and activated during
 122                 boot.</para>
 123         </refsect1>
 124
 125         <refsect1>
 126                 <title>Options</title>
 127
 128                 <para>Swap files must include a [Swap] section, which
 129                 carries information about the swap device it
 130                 supervises. A number of options that may be used in
 131                 this section are shared with other unit types. These
 132                 options are documented in
 133                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 134                 and
 135                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
 136                 options specific to the [Swap] section of swap units
 137                 are the following:</para>
 138
 139                 <variablelist class='unit-directives'>
 140
 141                         <varlistentry>
 142                                 <term><varname>What=</varname></term>
 143                                 <listitem><para>Takes an absolute path
 144                                 of a device node or file to use for
 145                                 paging. See
 146                                 <citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 147                                 for details. If this refers to a
 148                                 device node, a dependency on the
 149                                 respective device unit is
 150                                 automatically created. (See
 151                                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 152                                 for more information.) If this refers
 153                                 to a file, a dependency on the
 154                                 respective mount unit is automatically
 155                                 created. (See
 156                                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 157                                 for more information.) This option is
 158                                 mandatory.</para></listitem>
 159                         </varlistentry>
 160
 161                         <varlistentry>
 162                                 <term><varname>Priority=</varname></term>
 163
 164                                 <listitem><para>Swap priority to use
 165                                 when activating the swap device or
 166                                 file. This takes an integer. This
 167                                 setting is optional.</para></listitem>
 168                         </varlistentry>
 169
 170                         <varlistentry>
 171                                 <term><varname>TimeoutSec=</varname></term>
 172                                 <listitem><para>Configures the time to
 173                                 wait for the swapon command to
 174                                 finish. If a command does not exit
 175                                 within the configured time the swap
 176                                 will be considered failed and be shut
 177                                 down again. All commands still running
 178                                 will be terminated forcibly via
 179                                 <constant>SIGTERM</constant>, and after another delay of
 180                                 this time with <constant>SIGKILL</constant>. (See
 181                                 <option>KillMode=</option> in
 182                                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
 183                                 Takes a unit-less value in seconds, or
 184                                 a time span value such as "5min
 185                                 20s". Pass 0 to disable the timeout
 186                                 logic. Defaults to
 187                                 90s.</para></listitem>
 188                         </varlistentry>
 189                 </variablelist>
 190
 191                 <para>Check
 192                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 193                 and
 194                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 195                 for more settings.</para>
 196         </refsect1>
 197
 198         <refsect1>
 199                   <title>See Also</title>
 200                   <para>
 201                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 202                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 203                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 204                           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 205                           <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 206                           <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 207                           <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 208                           <citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 209                           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 210                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 211                   </para>
 212         </refsect1>
 213
 214 </refentry>