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first draft for Timers #6

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first draft for Timers #6

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67 changes: 67 additions & 0 deletions init-policy.sgml
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Expand Up @@ -1353,6 +1353,73 @@ fi
</sect>
</chapt>

<chapt id="timermaint">
<heading>Maintaining a Scheduled job</heading>

<sect id="backgroundtimers">
<heading>Background</heading>
<p>
There are a variety of different ways of job on different schedules.
The traditional approach uses the packages <prgn>cron</prgn>
<!-- and <prgn>anacron</prgn> --> with configuration files in
<file>/etc/cron.d</file> that must follow a special layout.
<!--
and standard scripts linked in
<file>/etc/cron.hourly|daily|weekly|monthly</file>-->
</p>
<p>
This functionality can now also be provided by native systemd timers.
To maintaint compatability with SysV Init; packages
that ships native timers must also ship corresponding crontabs.
</p>
<p>
These cron jobs must then also ensure that systemd is not
currently running to avoid duplicate execution.
</p>
</sect>

<sect id="systemdtimers">
<heading>Unit Files</heading>
<p>
Unit files are documented via the systemd man pages, see
<manref name="systemd.timer" section="5">,
<manref name="systemd.unit" section="5">,
<manref name="systemd.service" section="5">,
<manref name="systemd.directives" section="5">,
and related pages.
<p>
<p>
You basically need to provide a timer with a
<tt>[Install]</tt> section and a matching service.
The service will be started by the timer.
You may add a <tt>RefuseManualStart=yes</tt> directive
in the service to forbid manual execution.
</p>
<p>
These timers can be enabled in your maintainer script
by using <prgn>dh_systemd_enable</prgn>
and <prgn>dh_systemd_start</prgn>.
</p>

</sect>
<sect id="crontimers">
<heading>Crontabs</heading>
<p>
Crontab files are documented via your cron-daemon man pages, see
<manref name="crontab" section="5">,
and related pages. They must follow point 9.5 of the Debian Policy.
</p>
<p>
A canonical way to both ensure that systemd is not currently running, and to comply with
this point of the policy: <tt>The scripts or crontab entries in these directories should check if all necessary programs are installed before they try to execute them</tt> ; would be:
</p>
<p>
<tt>m h d m w user test -e /run/systemd/system || test -e /usr/bin/<var>pkg</var> && /usr/bin/<var>pkg</var></tt>
</p>
</sect>
</chapt>


<chapt id="initsysmaint">
<heading>Maintaining an Init System</heading>
<sect id="sbininit">
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