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2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
5
6<refentry id="systemd-notify"
7    xmlns:xi="http://www.w3.org/2001/XInclude">
8
9  <refentryinfo>
10    <title>systemd-notify</title>
11    <productname>systemd</productname>
12  </refentryinfo>
13
14  <refmeta>
15    <refentrytitle>systemd-notify</refentrytitle>
16    <manvolnum>1</manvolnum>
17  </refmeta>
18
19  <refnamediv>
20    <refname>systemd-notify</refname>
21    <refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
22  </refnamediv>
23
24  <refsynopsisdiv>
25    <cmdsynopsis>
26      <command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
27    </cmdsynopsis>
28  </refsynopsisdiv>
29
30  <refsect1>
31    <title>Description</title>
32
33    <para><command>systemd-notify</command> may be called by daemon
34    scripts to notify the init system about status changes. It can be
35    used to send arbitrary information, encoded in an
36    environment-block-like list of strings. Most importantly, it can be
37    used for start-up completion notification.</para>
38
39    <para>This is mostly just a wrapper around
40    <function>sd_notify()</function> and makes this functionality
41    available to shell scripts. For details see
42    <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
43    </para>
44
45    <para>The command line may carry a list of environment variables
46    to send as part of the status update.</para>
47
48    <para>Note that systemd will refuse reception of status updates from this command unless
49    <varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
50
51    <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
52    the sending process is still around at the time PID 1 processes the message, or if the sending process is
53    explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
54    off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
55    <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
56    <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
57    attribute the message to the unit, and thus will ignore it, even if <varname>NotifyAccess=</varname><option>all
58    </option> is set for it. When <option>--no-block</option> is used, all synchronization for reception of notifications
59    is disabled, and hence the aforementioned race may occur if the invoking process is not the service manager or spawned
60    by the service manager.</para>
61
62    <para>Hence, <command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function>
63    pretending to have the PID of the invoking process. This will only succeed when invoked with sufficient privileges.
64    On failure, it will then fall back to invoking it under its own PID. This behaviour is useful in order that when
65    the tool is invoked from a shell script the shell process — and not the <command>systemd-notify</command> process
66    — appears as sender of the message, which in turn is helpful if the shell process is the main process of a service,
67    due to the limitations of <varname>NotifyAccess=</varname><option>all</option>. Use the <option>--pid=</option>
68    switch to tweak this behaviour.</para>
69
70  </refsect1>
71
72  <refsect1>
73    <title>Options</title>
74
75    <para>The following options are understood:</para>
76
77    <variablelist>
78      <varlistentry>
79        <term><option>--ready</option></term>
80
81        <listitem><para>Inform the init system about service start-up
82        completion. This is equivalent to <command>systemd-notify
83        READY=1</command>. For details about the semantics of this
84        option see
85        <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
86      </varlistentry>
87
88      <varlistentry>
89        <term><option>--pid=</option></term>
90
91        <listitem><para>Inform the service manager about the main PID of the daemon. Takes a PID as
92        argument. If the argument is specified as <literal>auto</literal> or omitted, the PID of the process
93        that invoked <command>systemd-notify</command> is used, except if that's the service manager. If the
94        argument is specified as <literal>self</literal>, the PID of the <command>systemd-notify</command>
95        command itself is used, and if <literal>parent</literal> is specified the calling process' PID is
96        used — even if it is the service manager. This is equivalent to <command>systemd-notify
97        MAINPID=$PID</command>. For details about the semantics of this option see
98        <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
99      </varlistentry>
100
101      <varlistentry>
102        <term><option>--uid=</option><replaceable>USER</replaceable></term>
103
104        <listitem><para>Set the user ID to send the notification from. Takes a UNIX user name or numeric UID. When
105        specified the notification message will be sent with the specified UID as sender, in place of the user the
106        command was invoked as. This option requires sufficient privileges in order to be able manipulate the user
107        identity of the process.</para></listitem>
108      </varlistentry>
109
110      <varlistentry>
111        <term><option>--status=</option></term>
112
113        <listitem><para>Send a free-form status string for the daemon
114        to the init systemd. This option takes the status string as
115        argument. This is equivalent to <command>systemd-notify
116        STATUS=…</command>. For details about the semantics of this
117        option see
118        <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
119      </varlistentry>
120
121      <varlistentry>
122        <term><option>--booted</option></term>
123
124        <listitem><para>Returns 0 if the system was booted up with
125        systemd, non-zero otherwise. If this option is passed, no
126        message is sent. This option is hence unrelated to the other
127        options. For details about the semantics of this option, see
128        <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
129        alternate way to check for this state is to call
130        <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
131        with the <command>is-system-running</command> command. It will
132        return <literal>offline</literal> if the system was not booted
133        with systemd.  </para></listitem>
134      </varlistentry>
135
136      <varlistentry>
137        <term><option>--no-block</option></term>
138
139        <listitem><para>Do not synchronously wait for the requested operation to finish.  Use of this option
140        is only recommended when <command>systemd-notify</command> is spawned by the service manager, or when
141        the invoking process is directly spawned by the service manager and has enough privileges to allow
142        <command>systemd-notify</command> to send the notification on its behalf. Sending notifications with
143        this option set is prone to race conditions in all other cases.</para></listitem>
144      </varlistentry>
145
146      <xi:include href="standard-options.xml" xpointer="help" />
147      <xi:include href="standard-options.xml" xpointer="version" />
148    </variablelist>
149
150  </refsect1>
151
152  <refsect1>
153    <title>Exit status</title>
154
155    <para>On success, 0 is returned, a non-zero failure code
156    otherwise.</para>
157  </refsect1>
158
159  <refsect1>
160    <title>Example</title>
161
162    <example>
163      <title>Start-up Notification and Status Updates</title>
164
165      <para>A simple shell daemon that sends start-up notifications
166      after having set up its communication channel. During runtime it
167      sends further status updates to the init system:</para>
168
169      <programlisting>#!/bin/sh
170
171mkfifo /tmp/waldo
172systemd-notify --ready --status="Waiting for data…"
173
174while : ; do
175        read -r a &lt; /tmp/waldo
176        systemd-notify --status="Processing $a"
177
178        # Do something with $a …
179
180        systemd-notify --status="Waiting for data…"
181done</programlisting>
182    </example>
183  </refsect1>
184
185  <refsect1>
186    <title>See Also</title>
187    <para>
188      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
189      <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
190      <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
191      <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
192      <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
193    </para>
194  </refsect1>
195
196</refentry>
197