man/systemd-notify.xml

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