man/systemd-notify.xml - systemd - Git at Google

 <?xml version='1.0'?> <!--*-nxml-*-->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

 <refentry id="systemd-notify"
     xmlns:xi="http://www.w3.org/2001/XInclude">

   <refentryinfo>
     <title>systemd-notify</title>
     <productname>systemd</productname>
   </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. When <option>--no-block</option> is used, all synchronization for reception of notifications
     is disabled, and hence the aforementioned race may occur if the invoking process is not the service manager or spawned
     by the service manager.</para>

     <para>Hence, <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>. Use the <option>--pid=</option>
     switch to tweak this behaviour.</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 service manager about the main PID of the daemon. Takes a PID as
         argument. If the argument is specified as <literal>auto</literal> or omitted, the PID of the process
         that invoked <command>systemd-notify</command> is used, except if that's the service manager. If the
         argument is specified as <literal>self</literal>, the PID of the <command>systemd-notify</command>
         command itself is used, and if <literal>parent</literal> is specified the calling process' PID is
         used — even if it is the service manager. 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>--uid=</option><replaceable>USER</replaceable></term>

         <listitem><para>Set the user ID to send the notification from. Takes a UNIX user name or numeric UID. When
         specified the notification message will be sent with the specified UID as sender, in place of the user the
         command was invoked as. This option requires sufficient privileges in order to be able manipulate the user
         identity of the process.</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>

       <varlistentry>
         <term><option>--no-block</option></term>

         <listitem><para>Do not synchronously wait for the requested operation to finish.  Use of this option
         is only recommended when <command>systemd-notify</command> is spawned by the service manager, or when
         the invoking process is directly spawned by the service manager and has enough privileges to allow
         <command>systemd-notify</command> to send the notification on its behalf. Sending notifications with
         this option set is prone to race conditions in all other cases.</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 &lt; /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>
	<?xml version='1.0'?> <!---nxml--->
	<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
	"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
	<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

	<refentry id="systemd-notify"
	xmlns:xi="http://www.w3.org/2001/XInclude">

	<refentryinfo>
	<title>systemd-notify</title>
	<productname>systemd</productname>
	</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. When <option>--no-block</option> is used, all synchronization for reception of notifications
	is disabled, and hence the aforementioned race may occur if the invoking process is not the service manager or spawned
	by the service manager.</para>

	<para>Hence, <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>. Use the <option>--pid=</option>
	switch to tweak this behaviour.</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 service manager about the main PID of the daemon. Takes a PID as
	argument. If the argument is specified as <literal>auto</literal> or omitted, the PID of the process
	that invoked <command>systemd-notify</command> is used, except if that's the service manager. If the
	argument is specified as <literal>self</literal>, the PID of the <command>systemd-notify</command>
	command itself is used, and if <literal>parent</literal> is specified the calling process' PID is
	used — even if it is the service manager. 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>--uid=</option><replaceable>USER</replaceable></term>

	<listitem><para>Set the user ID to send the notification from. Takes a UNIX user name or numeric UID. When
	specified the notification message will be sent with the specified UID as sender, in place of the user the
	command was invoked as. This option requires sufficient privileges in order to be able manipulate the user
	identity of the process.</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>

	<varlistentry>
	<term><option>--no-block</option></term>

	<listitem><para>Do not synchronously wait for the requested operation to finish. Use of this option
	is only recommended when <command>systemd-notify</command> is spawned by the service manager, or when
	the invoking process is directly spawned by the service manager and has enough privileges to allow
	<command>systemd-notify</command> to send the notification on its behalf. Sending notifications with
	this option set is prone to race conditions in all other cases.</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>