From e96d6be763014be75d480fde503d0b77f41194a0 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 5 Apr 2012 22:08:10 +0200
Subject: systemd: add hardware watchdog support

This adds minimal hardware watchdog support to PID 1. The idea is that
PID 1 supervises and watchdogs system services, while the hardware
watchdog is used to supervise PID 1.

This adds two hardware watchdog configuration options, for the runtime
watchdog and for a shutdown watchdog. The former is active during normal
operation, the latter only at reboots to ensure that if a clean reboot
times out we reboot nonetheless.

If the runtime watchdog is enabled PID 1 will automatically wake up at
half the configured interval and write to the watchdog daemon.

By default we enable the shutdown watchdog, but leave the runtime
watchdog disabled in order not to break independent hardware watchdog
daemons people might be using.

This is only the most basic hookup. If necessary we can later on hook
up the watchdog ping more closely with services deemed crucial.
---
 man/systemd.conf.xml | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

(limited to 'man')

diff --git a/man/systemd.conf.xml b/man/systemd.conf.xml
index ba144da8cf..c7890287b5 100644
--- a/man/systemd.conf.xml
+++ b/man/systemd.conf.xml
@@ -149,6 +149,51 @@
                                 controllers in separate
                                 hierarchies.</para></listitem>
                         </varlistentry>
+
+                        <varlistentry>
+                                <term><varname>RuntimeWatchdogSec=</varname></term>
+                                <term><varname>ShutdownWatchdogSec=</varname></term>
+
+                                <listitem><para>Configure the hardware
+                                watchdog at runtime and at
+                                reboot. Takes a timeout value in
+                                seconds (or in other time units if
+                                suffixed with <literal>ms</literal>,
+                                <literal>min</literal>,
+                                <literal>h</literal>,
+                                <literal>d</literal>,
+                                <literal>w</literal>). If
+                                <varname>RuntimeWatchdogSec=</varname>
+                                is set to a non-zero value the
+                                watchdog hardware
+                                (<filename>/dev/watchdog</filename>)
+                                will be programmed to automatically
+                                reboot the system if it is not
+                                contacted within the specified timeout
+                                interval. The system manager will
+                                ensure to contact it at least once in
+                                half the specified timeout
+                                interval. This feature requires a
+                                hardware watchdog device to be
+                                present, as it is commonly the case in
+                                embedded and server systems. Not all
+                                hardware watchdogs allow configuration
+                                of the reboot timeout, in which case
+                                the closest available timeout is
+                                picked. <varname>ShutdownWatchdogSec=</varname>
+                                may be used to configure the hardware
+                                watchdog when the system is asked to
+                                reboot. It works as a safety net to
+                                ensure that the reboot takes place
+                                even if a clean reboot attempt times
+                                out. By default
+                                <varname>RuntimeWatchdogSec=</varname>
+                                defaults to 0 (off), and
+                                <varname>ShutdownWatchdogSec=</varname>
+                                to 10min. These settings have no
+                                effect if a hardware watchdog is not
+                                available.</para></listitem>
+                        </varlistentry>
                 </variablelist>
         </refsect1>
 
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