man/systemd-volatile-root.service.xml

   1 <?xml version="1.0"?>
   2 <!--*-nxml-*-->
   3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   4   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   5 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   6 <refentry id="systemd-volatile-root.service">
   7
   8   <refentryinfo>
   9     <title>systemd-volatile-root.service</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>systemd-volatile-root.service</refentrytitle>
  15     <manvolnum>8</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>systemd-volatile-root.service</refname>
  20     <refname>systemd-volatile-root</refname>
  21     <refpurpose>Make the root file system volatile</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><filename>systemd-volatile-root.service</filename></para>
  26     <para><filename>/usr/lib/systemd/systemd-volatile-root</filename></para>
  27   </refsynopsisdiv>
  28
  29   <refsect1>
  30     <title>Description</title>
  31
  32     <para><filename>systemd-volatile-root.service</filename> is a service that replaces the root directory with a
  33     volatile memory file system (<literal>tmpfs</literal>), mounting the original (non-volatile)
  34     <filename>/usr/</filename> inside it read-only. This way, vendor data from <filename>/usr/</filename> is available as
  35     usual, but all configuration data in <filename>/etc/</filename>, all state data in <filename>/var/</filename> and all
  36     other resources stored directly under the root directory are reset on boot and lost at shutdown, enabling fully
  37     stateless systems.</para>
  38
  39     <para>This service is only enabled if full volatile mode is selected, for example by specifying
  40     <literal>systemd.volatile=yes</literal> on the kernel command line. This service runs only in the initrd,
  41     before the system transitions to the host's root directory. Note that this service is not used if
  42     <literal>systemd.volatile=state</literal> is used, as in that mode the root directory is non-volatile.
  43     </para>
  44   </refsect1>
  45
  46   <refsect1>
  47     <title>See Also</title>
  48     <para><simplelist type="inline">
  49       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
  50       <member><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
  51       <member><citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
  52     </simplelist></para>
  53   </refsect1>
  54
  55 </refentry>