man/systemd.swap.xml

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  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, and in
  79                 <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
  80                 which configure resource control settings for the
  81                 processes of the service.</para>
  82
  83                 <para>Swap units must be named after the devices
  84                 or files they control. Example: the swap device
  85                 <filename noindex='true'>/dev/sda5</filename> must be configured in a
  86                 unit file <filename>dev-sda5.swap</filename>. For
  87                 details about the escaping logic used to convert a
  88                 file system path to a unit name see
  89                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
  90
  91                 <para>All swap units automatically get the appropriate
  92                 dependencies on the devices or on the mount points
  93                 of the files they are activated from.</para>
  94
  95                 <para>Swap units with
  96                 <varname>DefaultDependencies=</varname> enabled
  97                 implicitly acquire a conflicting dependency to
  98                 <filename>umount.target</filename> so that they are
  99                 deactivated at shutdown.</para>
 100         </refsect1>
 101
 102         <refsect1>
 103                 <title><filename>fstab</filename></title>
 104
 105                 <para>Swap units may either be configured via unit
 106                 files, or via <filename>/etc/fstab</filename> (see
 107                 <citerefentry><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 108                 for details). Swaps listed in
 109                 <filename>/etc/fstab</filename> will be converted into
 110                 native units dynamically at boot and when the
 111                 configuration of the system manager is
 112                 reloaded. See
 113                 <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 114                 for details about the conversion.</para>
 115
 116                 <para>If a swap device or file is configured in both
 117                 <filename>/etc/fstab</filename> and a unit file, the
 118                 configuration in the latter takes precedence.</para>
 119
 120                 <para>Unless the <option>noauto</option> option is set
 121                 for them all swap units configured in
 122                 <filename>/etc/fstab</filename> are also added as
 123                 requirements to <filename>swap.target</filename>, so
 124                 that they are waited for and activated during
 125                 boot.</para>
 126         </refsect1>
 127
 128         <refsect1>
 129                 <title>Options</title>
 130
 131                 <para>Swap files must include a [Swap] section, which
 132                 carries information about the swap device it
 133                 supervises. A number of options that may be used in
 134                 this section are shared with other unit types. These
 135                 options are documented in
 136                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 137                 and
 138                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>. The
 139                 options specific to the [Swap] section of swap units
 140                 are the following:</para>
 141
 142                 <variablelist class='unit-directives'>
 143
 144                         <varlistentry>
 145                                 <term><varname>What=</varname></term>
 146                                 <listitem><para>Takes an absolute path
 147                                 of a device node or file to use for
 148                                 paging. See
 149                                 <citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 150                                 for details. If this refers to a
 151                                 device node, a dependency on the
 152                                 respective device unit is
 153                                 automatically created. (See
 154                                 <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 155                                 for more information.) If this refers
 156                                 to a file, a dependency on the
 157                                 respective mount unit is automatically
 158                                 created. (See
 159                                 <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 160                                 for more information.) This option is
 161                                 mandatory.</para></listitem>
 162                         </varlistentry>
 163
 164                         <varlistentry>
 165                                 <term><varname>Priority=</varname></term>
 166
 167                                 <listitem><para>Swap priority to use
 168                                 when activating the swap device or
 169                                 file. This takes an integer. This
 170                                 setting is optional.</para></listitem>
 171                         </varlistentry>
 172
 173                         <varlistentry>
 174                                 <term><varname>TimeoutSec=</varname></term>
 175                                 <listitem><para>Configures the time to
 176                                 wait for the swapon command to
 177                                 finish. If a command does not exit
 178                                 within the configured time, the swap
 179                                 will be considered failed and be shut
 180                                 down again. All commands still running
 181                                 will be terminated forcibly via
 182                                 <constant>SIGTERM</constant>, and after another delay of
 183                                 this time with <constant>SIGKILL</constant>. (See
 184                                 <option>KillMode=</option> in
 185                                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>.)
 186                                 Takes a unit-less value in seconds, or
 187                                 a time span value such as "5min
 188                                 20s". Pass 0 to disable the timeout
 189                                 logic. Defaults to
 190                                 90s.</para></listitem>
 191                         </varlistentry>
 192                 </variablelist>
 193
 194                 <para>Check
 195                 <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 196                 and
 197                 <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 198                 for more settings.</para>
 199         </refsect1>
 200
 201         <refsect1>
 202                   <title>See Also</title>
 203                   <para>
 204                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 205                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 206                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 207                           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 208                           <citerefentry><refentrytitle>systemd.kill</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 209                           <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 210                           <citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 211                           <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 212                           <citerefentry><refentrytitle>swapon</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 213                           <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 214                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 215                   </para>
 216         </refsect1>
 217
 218 </refentry>