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-rw-r--r--man/systemd.offline-updates.xml41
1 files changed, 25 insertions, 16 deletions
diff --git a/man/systemd.offline-updates.xml b/man/systemd.offline-updates.xml
index 07a5225512..22aa0354a8 100644
--- a/man/systemd.offline-updates.xml
+++ b/man/systemd.offline-updates.xml
@@ -86,34 +86,42 @@
</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 after all file systems have been mounted.</para>
</listitem>
<listitem>
- <para>As the first step, the update script should check if the
+ <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
- script. In case it does not exists or points to a different location, the script must exit
+ 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.</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>
@@ -150,7 +158,8 @@
<listitem>
<para>The update service should declare <varname>DefaultDependencies=false</varname>,
- and pull in any services it requires explicitly.</para>
+ <varname>Requires=sysinit.target</varname>, <varname>After=sysinit.target</varname>,
+ and explicitly pull in any other services it requires.</para>
</listitem>
</orderedlist>
</refsect1>