systemd/man/sd_watchdog_enabled.xml
Tom Gundersen 12b42c7667 man: revert dynamic paths for split-usr setups
This did not really work out as we had hoped. Trying to do this upstream
introduced several problems that probably makes it better suited as a
downstream patch after all. At any rate, it is not releaseable in the
current state, so we at least need to revert this before the release.

 * by adjusting the path to binaries, but not do the same thing to the
   search path we end up with inconsistent man-pages. Adjusting the search
   path too would be quite messy, and it is not at all obvious that this is
   worth the effort, but at any rate it would have to be done before we
   could ship this.

 * this means that distributed man-pages does not make sense as they depend
   on config options, and for better or worse we are still distributing
   man pages, so that is something that definitely needs sorting out before
   we could ship with this patch.

 * we have long held that split-usr is only minimally supported in order
   to boot, and something we hope will eventually go away. So before we start
   adding even more magic/effort in order to make this work nicely, we should
   probably question if it makes sense at all.
2015-06-18 19:47:44 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id="sd_watchdog_enabled"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_watchdog_enabled</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_watchdog_enabled</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_watchdog_enabled</refname>
<refpurpose>Check whether the service manager expects watchdog keep-alive notifications from a service</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_watchdog_enabled</function></funcdef>
<paramdef>int <parameter>unset_environment</parameter></paramdef>
<paramdef>uint64_t *<parameter>usec</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_watchdog_enabled()</function> may be called by
a service to detect whether the service manager expects regular
keep-alive watchdog notification events from it, and the timeout
after which the manager will act on the service if it did not get
such a notification.</para>
<para>If the <varname>$WATCHDOG_USEC</varname> environment
variable is set, and the <varname>$WATCHDOG_PID</varname> variable
is unset or set to the PID of the current process, the service
manager expects notifications from this process. The manager will
usually terminate a service when it does not get a notification
message within the specified time after startup and after each
previous message. It is recommended that a daemon sends a
keep-alive notification message to the service manager every half
of the time returned here. Notification messages may be sent with
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
with a message string of <literal>WATCHDOG=1</literal>.</para>
<para>If the <parameter>unset_environment</parameter> parameter is
non-zero, <function>sd_watchdog_enabled()</function> will unset
the <varname>$WATCHDOG_USEC</varname> and
<varname>$WATCHDOG_PID</varname> environment variables before
returning (regardless of whether the function call itself
succeeded or not). Those variables are no longer inherited by
child processes. Further calls to
<function>sd_watchdog_enabled()</function> will also return with
zero.</para>
<para>If the <parameter>usec</parameter> parameter is non-NULL,
<function>sd_watchdog_enabled()</function> will write the timeout
in µs for the watchdog logic to it.</para>
<para>To enable service supervision with the watchdog logic, use
<varname>WatchdogSec=</varname> in service files. See
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On failure, this call returns a negative errno-style error
code. If the service manager expects watchdog keep-alive
notification messages to be sent, &gt; 0 is returned, otherwise 0
is returned. Only if the return value is &gt; 0, the
<parameter>usec</parameter> parameter is valid after the
call.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
<para>Internally, this functions parses the
<varname>$WATCHDOG_PID</varname> and
<varname>$WATCHDOG_USEC</varname> environment variable. The call
will ignore these variables if <varname>$WATCHDOG_PID</varname>
does not contain the PID of the current process, under the
assumption that in that case, the variables were set for a
different process further up the process tree.</para>
</refsect1>
<refsect1>
<title>Environment</title>
<variablelist class='environment-variables'>
<varlistentry>
<term><varname>$WATCHDOG_PID</varname></term>
<listitem><para>Set by the system manager for supervised
process for which watchdog support is enabled, and contains
the PID of that process. See above for
details.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>$WATCHDOG_USEC</varname></term>
<listitem><para>Set by the system manager for supervised
process for which watchdog support is enabled, and contains
the watchdog timeout in µs See above for
details.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>History</title>
<para>The watchdog functionality and the
<varname>$WATCHDOG_USEC</varname> variable were added in
systemd-41.</para>
<para><function>sd_watchdog_enabled()</function> function was
added in systemd-209. Since that version the
<varname>$WATCHDOG_PID</varname> variable is also set.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>