<?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">
-<!--
- SPDX-License-Identifier: LGPL-2.1+
-
- This file is part of systemd.
-
- Copyright 2012 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
-
- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="systemd-fstab-generator">
<refentryinfo>
<title>systemd-fstab-generator</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
lost at shutdown, as <filename>/etc</filename> and <filename>/var</filename> will be served from the (initially
unpopulated) volatile memory file system.</para>
- <para>If set to <option>state</option> the generator will leave the root
- directory mount point unaltered, however will mount a <literal>tmpfs</literal> file system to
- <filename>/var</filename>. In this mode the normal system configuration (i.e. the contents of
- <literal>/etc</literal>) is in effect (and may be modified during system runtime), however the system state
- (i.e. the contents of <literal>/var</literal>) is reset at boot and lost at shutdown.</para>
+ <para>If set to <option>state</option> the generator will leave the root directory mount point unaltered,
+ however will mount a <literal>tmpfs</literal> file system to <filename>/var</filename>. In this mode the normal
+ system configuration (i.e. the contents of <literal>/etc</literal>) is in effect (and may be modified during
+ system runtime), however the system state (i.e. the contents of <literal>/var</literal>) is reset at boot and
+ lost at shutdown.</para>
+
+ <para>If this setting is set to <literal>overlay</literal> the root file system is set up as
+ <literal>overlayfs</literal> mount combining the read-only root directory with a writable
+ <literal>tmpfs</literal>, so that no modifications are made to disk, but the file system may be modified
+ nonetheless with all changes being lost at reboot.</para>
<para>Note that in none of these modes the root directory, <filename>/etc</filename>, <filename>/var</filename>
or any other resources stored in the root file system are physically removed. It's thus safe to boot a system
that is normally operated in non-volatile mode temporarily into volatile mode, without losing data.</para>
- <para>Note that enabling this setting will only work correctly on operating systems that can boot up with only
- <filename>/usr</filename> mounted, and are able to automatically populate <filename>/etc</filename>, and also
- <filename>/var</filename> in case of <literal>systemd.volatile=yes</literal>.</para></listitem>
+ <para>Note that with the exception of <literal>overlay</literal> mode, enabling this setting will only work
+ correctly on operating systems that can boot up with only <filename>/usr</filename> mounted, and are able to
+ automatically populate <filename>/etc</filename>, and also <filename>/var</filename> in case of
+ <literal>systemd.volatile=yes</literal>.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>