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systemd-notify.xml
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systemd-notify.xml
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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">
<!--
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="systemd-notify"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>systemd-notify</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>systemd-notify</refentrytitle>
<manvolnum>1</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-notify</refname>
<refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>systemd-notify</command> may be called by daemon
scripts to notify the init system about status changes. It can be
used to send arbitrary information, encoded in an
environment-block-like list of strings. Most importantly, it can be
used for start-up completion notification.</para>
<para>This is mostly just a wrapper around
<function>sd_notify()</function> and makes this functionality
available to shell scripts. For details see
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
</para>
<para>The command line may carry a list of environment variables
to send as part of the status update.</para>
<para>Note that systemd will refuse reception of status updates from this command unless
<varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
<para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
the sending process is still around at the time PID 1 processes the message, or if the sending process is
explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
<varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
<function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
attribute the message to the unit, and thus will ignore it, even if
<varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
<para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
</refsect1>
<refsect1>
<title>Options</title>
<para>The following options are understood:</para>
<variablelist>
<varlistentry>
<term><option>--ready</option></term>
<listitem><para>Inform the init system about service start-up
completion. This is equivalent to <command>systemd-notify
READY=1</command>. For details about the semantics of this
option see
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--pid=</option></term>
<listitem><para>Inform the init system about the main PID of
the daemon. Takes a PID as argument. If the argument is
omitted, the PID of the process that invoked
<command>systemd-notify</command> is used. This is equivalent
to <command>systemd-notify MAINPID=$PID</command>. For details
about the semantics of this option see
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--status=</option></term>
<listitem><para>Send a free-form status string for the daemon
to the init systemd. This option takes the status string as
argument. This is equivalent to <command>systemd-notify
STATUS=…</command>. For details about the semantics of this
option see
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--booted</option></term>
<listitem><para>Returns 0 if the system was booted up with
systemd, non-zero otherwise. If this option is passed, no
message is sent. This option is hence unrelated to the other
options. For details about the semantics of this option, see
<citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
alternate way to check for this state is to call
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
with the <command>is-system-running</command> command. It will
return <literal>offline</literal> if the system was not booted
with systemd. </para></listitem>
</varlistentry>
<xi:include href="standard-options.xml" xpointer="help" />
<xi:include href="standard-options.xml" xpointer="version" />
</variablelist>
</refsect1>
<refsect1>
<title>Exit status</title>
<para>On success, 0 is returned, a non-zero failure code
otherwise.</para>
</refsect1>
<refsect1>
<title>Example</title>
<example>
<title>Start-up Notification and Status Updates</title>
<para>A simple shell daemon that sends start-up notifications
after having set up its communication channel. During runtime it
sends further status updates to the init system:</para>
<programlisting>#!/bin/bash
mkfifo /tmp/waldo
systemd-notify --ready --status="Waiting for data…"
while : ; do
read a < /tmp/waldo
systemd-notify --status="Processing $a"
# Do something with $a …
systemd-notify --status="Waiting for data…"
done</programlisting>
</example>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>