<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- This file is part of systemd.
-
- Copyright 2013 Lennart Poettering
- Copyright 2016 Zbigniew Jędrzejewski-Szmek
-
- 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/>.
--->
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
<refentry id="systemd.offline-updates">
<refentryinfo>
<title>systemd.offline-updates</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<listitem>
<para>The package manager prepares system updates by downloading all (RPM or DEB or
whatever) packages to update off-line in a special directory
- <filename noindex="true">/var/lib/system-update</filename> (or
+ <filename index="false">/var/lib/system-update</filename> (or
another directory of the package/upgrade manager's choice).</para>
</listitem>
<listitem>
<para>When the user OK'ed the update, the symlink <filename>/system-update</filename> is
- created that points to <filename noindex="true">/var/lib/system-update</filename> (or
+ created that points to <filename index="false">/var/lib/system-update</filename> (or
wherever the directory with the upgrade files is located) and the system is rebooted. This
symlink is in the root directory, since we need to check for it very early at boot, at a
time where <filename>/var</filename> is not available yet.</para>
<listitem>
<para>Very early in the new boot
- <citerefentry><refentrytitle>systemd-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
checks whether <filename>/system-update</filename> exists. If so, it (temporarily and for
this boot only) redirects (i.e. symlinks) <filename>default.target</filename> to
- <filename>system-update.target</filename>, a special target that is pulls in the base system
+ <filename>system-update.target</filename>, a special target that pulls in the base system
(i.e. <filename>sysinit.target</filename>, so that all file systems are mounted but little
else) and the system update units.</para>
</listitem>
<listitem>
- <para>The system now continues to boot into <filename>default.target</filename>, and thus
- into <filename>system-update.target</filename>. This target pulls in the system update unit,
- which starts the system update script after all file systems have been mounted.</para>
+ <para>The system now continues to boot into <filename>default.target</filename>, and
+ thus into <filename>system-update.target</filename>. This target pulls in all system
+ update units. Only one service should perform an update (see the next point), and all
+ the other ones should exit cleanly with a "success" return code and without doing
+ anything. Update services should be ordered after <filename>sysinit.target</filename>
+ so that the update starts after all file systems have been mounted.</para>
</listitem>
<listitem>
- <para>As the first step, the update script should check if the
- <filename>/system-update</filename> symlink points to the the location used by that update
- script. In case it does not exists or points to a different location, the script must exit
+ <para>As the first step, an update service should check if the
+ <filename>/system-update</filename> symlink points to the location used by that update
+ service. In case it does not exist or points to a different location, the service must exit
without error. It is possible for multiple update services to be installed, and for multiple
- update scripts to be launched in parallel, and only the one that corresponds to the tool
+ update services to be launched in parallel, and only the one that corresponds to the tool
that <emphasis>created</emphasis> the symlink before reboot should perform any actions. It
is unsafe to run multiple updates in parallel.</para>
</listitem>
<listitem>
- <para>The update script should now do its job. If applicable and possible, it should
- create a file system snapshot, then install all packages.
- After completion (regardless whether the update succeeded or failed) the machine
- must be rebooted, for example by calling <command>systemctl reboot</command>.
- In addition, on failure the script should revert to the old file system snapshot
- (without the symlink).</para>
+ <para>The update service should now do its job. If applicable and possible, it should
+ create a file system snapshot, then install all packages. After completion (regardless
+ whether the update succeeded or failed) the machine must be rebooted, for example by
+ calling <command>systemctl reboot</command>. In addition, on failure the script should
+ revert to the old file system snapshot (without the symlink).</para>
</listitem>
<listitem>
- <para>The system is rebooted. Since the <filename>/system-update</filename> symlink is gone,
- the generator won't redirect <filename>default.target</filename> after reboot and the
- system now boots into the default target again.</para>
+ <para>The upgrade scripts should exit only after the update is finished. It is expected
+ that the service which performs the upgrade will cause the machine to reboot after it
+ is done. If the <filename>system-update.target</filename> is successfully reached, i.e.
+ all update services have run, and the <filename>/system-update</filename> symlink still
+ exists, it will be removed and the machine rebooted as a safety measure.</para>
+ </listitem>
+
+ <listitem>
+ <para>After a reboot, now that the <filename>/system-update</filename> symlink is gone,
+ the generator won't redirect <filename>default.target</filename> anymore and the system
+ now boots into the default target again.</para>
</listitem>
</orderedlist>
</refsect1>
<orderedlist>
<listitem>
<para>To make things a bit more robust we recommend hooking the update script into
- <filename>system-update.target</filename> via a <filename noindex='true'>.wants/</filename>
+ <filename>system-update.target</filename> via a <filename index="false">.wants/</filename>
symlink in the distribution package, rather than depending on <command>systemctl
enable</command> in the postinst scriptlets of your package. More specifically, for your
update script create a .service file, without [Install] section, and then add a symlink like
- <filename noindex='true'>/usr/lib/systemd/system-update.target.wants/foobar.service</filename>
- → <filename noindex='true'>../foobar.service</filename> to your package.</para>
+ <filename index="false">/usr/lib/systemd/system-update.target.wants/foobar.service</filename>
+ → <filename index="false">../foobar.service</filename> to your package.</para>
</listitem>
<listitem>
<varname>FailureAction=</varname> makes sure that the specified unit is activated if your
script exits uncleanly (by non-zero error code, or signal/coredump). If your script succeeds
you should trigger the reboot in your own code, for example by invoking logind's
- <command>Reboot()</command> call or calling <command>systemct reboot</command>. See
- <ulink url="http://www.freedesktop.org/wiki/Software/systemd/logind">logind dbus API</ulink>
+ <command>Reboot()</command> call or calling <command>systemctl reboot</command>. See
+ <ulink url="https://www.freedesktop.org/wiki/Software/systemd/logind">logind dbus API</ulink>
for details.</para>
</listitem>
<listitem>
- <para>The update service should declare <varname>DefaultDependencies=false</varname>,
- and pull in any services it requires explicitly.</para>
+ <para>The update service should declare <varname>DefaultDependencies=no</varname>,
+ <varname>Requires=sysinit.target</varname>, <varname>After=sysinit.target</varname>,
+ <varname>After=system-update-pre.target</varname>, <varname>Before=system-update.target</varname>
+ and explicitly pull in any other services it requires.</para>
+ </listitem>
+
+ <listitem>
+ <para>It may be desirable to always run an auxiliary unit when booting
+ into offline-updates mode, which itself does not install updates. To
+ do this create a .service file with
+ <varname>Wants=system-update-pre.target</varname> and
+ <varname>Before=system-update-pre.target</varname> and add a symlink
+ to that file under
+ <filename index="false">/usr/lib/systemd/system-update.target.wants</filename>
+ .</para>
</listitem>
</orderedlist>
</refsect1>
<title>See also</title>
<para>
- <ulink url="http://www.freedesktop.org/wiki/Software/systemd/SystemUpdates/">Implementing Offline System Updates</ulink>,
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>dnf.plugin.system-upgrade</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry project='mankier'><refentrytitle>dnf.plugin.system-upgrade</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
projects / thirdparty / systemd.git / blobdiff