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man: watchdog documentation improvements
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@ -157,31 +157,27 @@
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<term><varname>RuntimeWatchdogSec=</varname></term>
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<term><varname>ShutdownWatchdogSec=</varname></term>
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<listitem><para>Configure the hardware watchdog at runtime and
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at reboot. Takes a timeout value in seconds (or in other time
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units if suffixed with <literal>ms</literal>,
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<literal>min</literal>, <literal>h</literal>,
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<literal>d</literal>, <literal>w</literal>). If
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<varname>RuntimeWatchdogSec=</varname> is set to a non-zero
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value, the watchdog hardware
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(<filename>/dev/watchdog</filename> or the path specified with
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<varname>WatchdogDevice=</varname> or the kernel option
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<varname>systemd.watchdog-device=</varname>) will be programmed
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to automatically reboot the system if it is not contacted within
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the specified timeout interval. The system manager will ensure
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to contact it at least once in half the specified timeout
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interval. This feature requires a hardware watchdog device to
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be present, as it is commonly the case in embedded and server
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systems. Not all hardware watchdogs allow configuration of the
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reboot timeout, in which case the closest available timeout is
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picked. <varname>ShutdownWatchdogSec=</varname> may be used to
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configure the hardware watchdog when the system is asked to
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reboot. It works as a safety net to ensure that the reboot
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takes place even if a clean reboot attempt times out. By
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default <varname>RuntimeWatchdogSec=</varname> defaults to 0
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(off), and <varname>ShutdownWatchdogSec=</varname> to 10min.
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These settings have no effect if a hardware watchdog is not
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available.</para></listitem>
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<listitem><para>Configure the hardware watchdog at runtime and at reboot. Takes a timeout value in seconds (or
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in other time units if suffixed with <literal>ms</literal>, <literal>min</literal>, <literal>h</literal>,
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<literal>d</literal>, <literal>w</literal>). If <varname>RuntimeWatchdogSec=</varname> is set to a non-zero
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value, the watchdog hardware (<filename>/dev/watchdog</filename> or the path specified with
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<varname>WatchdogDevice=</varname> or the kernel option <varname>systemd.watchdog-device=</varname>) will be
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programmed to automatically reboot the system if it is not contacted within the specified timeout interval. The
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system manager will ensure to contact it at least once in half the specified timeout interval. This feature
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requires a hardware watchdog device to be present, as it is commonly the case in embedded and server
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systems. Not all hardware watchdogs allow configuration of all possible reboot timeout values, in which case
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the closest available timeout is picked. <varname>ShutdownWatchdogSec=</varname> may be used to configure the
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hardware watchdog when the system is asked to reboot. It works as a safety net to ensure that the reboot takes
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place even if a clean reboot attempt times out. Note that the <varname>ShutdownWatchdogSec=</varname> timeout
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applies only to the second phase of the reboot, i.e. after all regular services are already terminated, and
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after the system and service manager process (PID 1) got replaced by the <filename>systemd-shutdown</filename>
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binary, see system <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for details. During the first phase of the shutdown operation the system and service manager remains running
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and hence <varname>RuntimeWatchdogSec=</varname> is still honoured. In order to define a timeout on this first
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phase of system shutdown, configure <varname>JobTimeoutSec=</varname> and <varname>JobTimeoutAction=</varname>
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in the <literal>[Unit]</literal> section of the <filename>shutdown.target</filename> unit. By default
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<varname>RuntimeWatchdogSec=</varname> defaults to 0 (off), and <varname>ShutdownWatchdogSec=</varname> to
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10min. These settings have no effect if a hardware watchdog is not available.</para></listitem>
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</varlistentry>
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<varlistentry>
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