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267 lines
14 KiB
XML
267 lines
14 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-notify"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-notify</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-notify</refentrytitle>
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<manvolnum>1</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-notify</refname>
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<refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
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</cmdsynopsis>
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<cmdsynopsis>
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<command>systemd-notify --exec <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg> ; <arg rep="repeat">CMDLINE</arg></command>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>systemd-notify</command> may be called by service scripts to notify the invoking service
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manager about status changes. It can be used to send arbitrary information, encoded in an
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environment-block-like list of strings. Most importantly, it can be used for start-up completion
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notification.</para>
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<para>This is mostly just a wrapper around <function>sd_notify()</function> and makes this functionality
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available to shell scripts. For details see
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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</para>
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<para>The command line may carry a list of environment variables to send as part of the status
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update.</para>
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<para>Note that systemd will refuse reception of status updates from this command unless
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<varname>NotifyAccess=</varname> is appropriately set for the service unit this command is called
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from. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
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details.</para>
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<para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only
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if either the sending process is still around at the time the service manager processes the message, or
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if the sending process is explicitly runtime-tracked by the service manager. The latter is the case if
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the service manager originally forked off the process, i.e. on all processes that match
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<varname>NotifyAccess=</varname><option>main</option> or
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<varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit
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sends an <function>sd_notify()</function> message and immediately exits, the service manager might not be
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able to properly attribute the message to the unit, and thus will ignore it, even if
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<varname>NotifyAccess=</varname><option>all</option> is set for it. To address this
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<command>systemd-notify</command> will wait until the notification message has been processed by the
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service manager. When <option>--no-block</option> is used, this synchronization for reception of
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notifications is disabled, and hence the aforementioned race may occur if the invoking process is not the
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service manager or spawned by the service manager.</para>
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<para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function>
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pretending to have the PID of the parent process of <command>systemd-notify</command> (i.e. the invoking
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process). This will only succeed when invoked with sufficient privileges. On failure, it will then fall
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back to invoking it under its own PID. This behaviour is useful in order that when the tool is invoked
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from a shell script the shell process — and not the <command>systemd-notify</command> process — appears
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as sender of the message, which in turn is helpful if the shell process is the main process of a service,
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due to the limitations of <varname>NotifyAccess=</varname><option>all</option>. Use the
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<option>--pid=</option> switch to tweak this behaviour.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The following options are understood:</para>
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<variablelist>
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<varlistentry>
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<term><option>--ready</option></term>
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<listitem><para>Inform the invoking service manager about service start-up or configuration reload
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completion. This is equivalent to <command>systemd-notify READY=1</command>. For details about the
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semantics of this option see
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--reloading</option></term>
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<listitem><para>Inform the invoking service manager about the beginning of a configuration reload
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cycle. This is equivalent to <command>systemd-notify RELOADING=1</command> (but implicitly also sets
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a <varname>MONOTONIC_USEC=</varname> field as required for <varname>Type=notify-reload</varname>
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services, see
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details). For details about the semantics of this option see
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--stopping</option></term>
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<listitem><para>Inform the invoking service manager about the beginning of the shutdown phase of the
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service. This is equivalent to <command>systemd-notify STOPPING=1</command>. For details about the
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semantics of this option see
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--pid=</option></term>
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<listitem><para>Inform the service manager about the main PID of the service. Takes a PID as
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argument. If the argument is specified as <literal>auto</literal> or omitted, the PID of the process
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that invoked <command>systemd-notify</command> is used, except if that's the service manager. If the
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argument is specified as <literal>self</literal>, the PID of the <command>systemd-notify</command>
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command itself is used, and if <literal>parent</literal> is specified the calling process' PID is
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used — even if it is the service manager. The latter is equivalent to <command>systemd-notify
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MAINPID=$PID</command>. For details about the semantics of this option see
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>If this switch is used in an <command>systemd-notify</command> invocation from a process that
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shall become the new main process of a service — and which is not the process forked off by the
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service manager (or the current main process) —, then it is essential to set
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<varname>NotifyAccess=all</varname> in the service unit file, or otherwise the notification will be
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ignored for security reasons. See
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--uid=</option><replaceable>USER</replaceable></term>
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<listitem><para>Set the user ID to send the notification from. Takes a UNIX user name or numeric UID. When
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specified the notification message will be sent with the specified UID as sender, in place of the user the
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command was invoked as. This option requires sufficient privileges in order to be able manipulate the user
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identity of the process.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--status=</option></term>
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<listitem><para>Send a free-form human readable status string for the daemon to the service
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manager. This option takes the status string as argument. This is equivalent to
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<command>systemd-notify STATUS=…</command>. For details about the semantics of this option see
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>. This
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information is shown in
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
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<command>status</command> output, among other places.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--booted</option></term>
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<listitem><para>Returns 0 if the system was booted up with systemd, non-zero otherwise. If this
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option is passed, no message is sent. This option is hence unrelated to the other options. For
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details about the semantics of this option, see
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<citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
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alternate way to check for this state is to call
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry> with
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the <command>is-system-running</command> command. It will return <literal>offline</literal> if the
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system was not booted with systemd. </para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--no-block</option></term>
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<listitem><para>Do not synchronously wait for the requested operation to finish. Use of this option
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is only recommended when <command>systemd-notify</command> is spawned by the service manager, or when
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the invoking process is directly spawned by the service manager and has enough privileges to allow
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<command>systemd-notify</command> to send the notification on its behalf. Sending notifications with
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this option set is prone to race conditions in all other cases.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--exec</option></term>
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<listitem><para>If specified <command>systemd-notify</command> will execute another command line
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after it completed its operation, replacing its own process. If used, the list of assignments to
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include in the message sent must be followed by a <literal>;</literal> character (as separate
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argument), followed by the command line to execute. This permits "chaining" of commands, i.e. issuing
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one operation, followed immediately by another, without changing PIDs.</para>
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<para>Note that many shells interpret <literal>;</literal> as their own separator for command lines,
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hence when <command>systemd-notify</command> is invoked from a shell the semicolon must usually be
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escaped as <literal>\;</literal>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--fd=</option></term>
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<listitem><para>Send a file descriptor along with the notification message. This is useful when
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invoked in services that have the <varname>FileDescriptorStoreMax=</varname> setting enabled, see
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details. The specified file descriptor must be passed to <command>systemd-notify</command> when
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invoked. This option may be used multiple times to pass multiple file descriptors in a single
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notification message.</para>
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<para>To use this functionality from a <command>bash</command> shell, use an expression like the following:</para>
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<programlisting>systemd-notify --fd=4 --fd=5 4</some/file 5</some/other/file</programlisting></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--fdname=</option></term>
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<listitem><para>Set a name to assign to the file descriptors passed via <option>--fd=</option> (see
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above). This controls the <literal>FDNAME=</literal> field. This setting may only be specified once,
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and applies to all file descriptors passed. Invoke this tool multiple times in case multiple file
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descriptors with different file descriptor names shall be submitted.</para></listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="help" />
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<xi:include href="standard-options.xml" xpointer="version" />
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Exit status</title>
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<para>On success, 0 is returned, a non-zero failure code
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otherwise.</para>
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</refsect1>
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<refsect1>
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<title>Example</title>
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<example>
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<title>Start-up Notification and Status Updates</title>
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<para>A simple shell daemon that sends start-up notifications after having set up its communication
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channel. During runtime it sends further status updates to the init system:</para>
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<programlisting>#!/bin/sh
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mkfifo /tmp/waldo
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systemd-notify --ready --status="Waiting for data…"
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while : ; do
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read -r a < /tmp/waldo
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systemd-notify --status="Processing $a"
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# Do something with $a …
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systemd-notify --status="Waiting for data…"
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done</programlisting>
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</example>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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