diff options
Diffstat (limited to 'man/systemd.offline-updates.xml')
| -rw-r--r-- | man/systemd.offline-updates.xml | 43 |
1 files changed, 27 insertions, 16 deletions
diff --git a/man/systemd.offline-updates.xml b/man/systemd.offline-updates.xml index 07a5225512..d673cf5db8 100644 --- a/man/systemd.offline-updates.xml +++ b/man/systemd.offline-updates.xml @@ -86,34 +86,44 @@ </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. 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> @@ -150,7 +160,8 @@ <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> |