man/systemd-notify.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   Copyright 2010 Lennart Poettering
   9 -->
  10
  11 <refentry id="systemd-notify"
  12     xmlns:xi="http://www.w3.org/2001/XInclude">
  13
  14   <refentryinfo>
  15     <title>systemd-notify</title>
  16     <productname>systemd</productname>
  17
  18     <authorgroup>
  19       <author>
  20         <contrib>Developer</contrib>
  21         <firstname>Lennart</firstname>
  22         <surname>Poettering</surname>
  23         <email>lennart@poettering.net</email>
  24       </author>
  25     </authorgroup>
  26   </refentryinfo>
  27
  28   <refmeta>
  29     <refentrytitle>systemd-notify</refentrytitle>
  30     <manvolnum>1</manvolnum>
  31   </refmeta>
  32
  33   <refnamediv>
  34     <refname>systemd-notify</refname>
  35     <refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
  36   </refnamediv>
  37
  38   <refsynopsisdiv>
  39     <cmdsynopsis>
  40       <command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
  41     </cmdsynopsis>
  42   </refsynopsisdiv>
  43
  44   <refsect1>
  45     <title>Description</title>
  46
  47     <para><command>systemd-notify</command> may be called by daemon
  48     scripts to notify the init system about status changes. It can be
  49     used to send arbitrary information, encoded in an
  50     environment-block-like list of strings. Most importantly, it can be
  51     used for start-up completion notification.</para>
  52
  53     <para>This is mostly just a wrapper around
  54     <function>sd_notify()</function> and makes this functionality
  55     available to shell scripts. For details see
  56     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  57     </para>
  58
  59     <para>The command line may carry a list of environment variables
  60     to send as part of the status update.</para>
  61
  62     <para>Note that systemd will refuse reception of status updates from this command unless
  63     <varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
  64
  65     <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
  66     the sending process is still around at the time PID 1 processes the message, or if the sending process is
  67     explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
  68     off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
  69     <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
  70     <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
  71     attribute the message to the unit, and thus will ignore it, even if
  72     <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
  73
  74     <para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
  75     have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
  76     it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
  77     invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
  78     sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
  79     limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
  80   </refsect1>
  81
  82   <refsect1>
  83     <title>Options</title>
  84
  85     <para>The following options are understood:</para>
  86
  87     <variablelist>
  88       <varlistentry>
  89         <term><option>--ready</option></term>
  90
  91         <listitem><para>Inform the init system about service start-up
  92         completion. This is equivalent to <command>systemd-notify
  93         READY=1</command>. For details about the semantics of this
  94         option see
  95         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
  96       </varlistentry>
  97
  98       <varlistentry>
  99         <term><option>--pid=</option></term>
 100
 101         <listitem><para>Inform the init system about the main PID of
 102         the daemon. Takes a PID as argument. If the argument is
 103         omitted, the PID of the process that invoked
 104         <command>systemd-notify</command> is used. This is equivalent
 105         to <command>systemd-notify MAINPID=$PID</command>. For details
 106         about the semantics of this option see
 107         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 108       </varlistentry>
 109
 110       <varlistentry>
 111         <term><option>--uid=</option><replaceable>USER</replaceable></term>
 112
 113         <listitem><para>Set the user ID to send the notification from. Takes a UNIX user name or numeric UID. When
 114         specified the notification message will be sent with the specified UID as sender, in place of the user the
 115         command was invoked as. This option requires sufficient privileges in order to be able manipulate the user
 116         identity of the process.</para></listitem>
 117       </varlistentry>
 118
 119       <varlistentry>
 120         <term><option>--status=</option></term>
 121
 122         <listitem><para>Send a free-form status string for the daemon
 123         to the init systemd. This option takes the status string as
 124         argument. This is equivalent to <command>systemd-notify
 125         STATUS=…</command>. For details about the semantics of this
 126         option see
 127         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 128       </varlistentry>
 129
 130       <varlistentry>
 131         <term><option>--booted</option></term>
 132
 133         <listitem><para>Returns 0 if the system was booted up with
 134         systemd, non-zero otherwise. If this option is passed, no
 135         message is sent. This option is hence unrelated to the other
 136         options. For details about the semantics of this option, see
 137         <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
 138         alternate way to check for this state is to call
 139         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 140         with the <command>is-system-running</command> command. It will
 141         return <literal>offline</literal> if the system was not booted
 142         with systemd.  </para></listitem>
 143       </varlistentry>
 144
 145       <xi:include href="standard-options.xml" xpointer="help" />
 146       <xi:include href="standard-options.xml" xpointer="version" />
 147     </variablelist>
 148
 149   </refsect1>
 150
 151   <refsect1>
 152     <title>Exit status</title>
 153
 154     <para>On success, 0 is returned, a non-zero failure code
 155     otherwise.</para>
 156   </refsect1>
 157
 158   <refsect1>
 159     <title>Example</title>
 160
 161     <example>
 162       <title>Start-up Notification and Status Updates</title>
 163
 164       <para>A simple shell daemon that sends start-up notifications
 165       after having set up its communication channel. During runtime it
 166       sends further status updates to the init system:</para>
 167
 168       <programlisting>#!/bin/bash
 169
 170 mkfifo /tmp/waldo
 171 systemd-notify --ready --status="Waiting for data…"
 172
 173 while : ; do
 174         read a &lt; /tmp/waldo
 175         systemd-notify --status="Processing $a"
 176
 177         # Do something with $a …
 178
 179         systemd-notify --status="Waiting for data…"
 180 done</programlisting>
 181     </example>
 182   </refsect1>
 183
 184   <refsect1>
 185     <title>See Also</title>
 186     <para>
 187       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 188       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 189       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 190       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 191       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 192     </para>
 193   </refsect1>
 194
 195 </refentry>