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diff --git a/src/libsystemd/sd_notify.xml b/src/libsystemd/sd_notify.xml new file mode 100644 index 0000000000..94542b80b8 --- /dev/null +++ b/src/libsystemd/sd_notify.xml @@ -0,0 +1,405 @@ +<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + This file is part of systemd. + + Copyright 2010 Lennart Poettering + + systemd is free software; you can redistribute it and/or modify it + under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 2.1 of the License, or + (at your option) any later version. + + systemd is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with systemd; If not, see <http://www.gnu.org/licenses/>. +--> + +<refentry id="sd_notify" + xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>sd_notify</title> + <productname>systemd</productname> + + <authorgroup> + <author> + <contrib>Developer</contrib> + <firstname>Lennart</firstname> + <surname>Poettering</surname> + <email>lennart@poettering.net</email> + </author> + </authorgroup> + </refentryinfo> + + <refmeta> + <refentrytitle>sd_notify</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_notify</refname> + <refname>sd_notifyf</refname> + <refname>sd_pid_notify</refname> + <refname>sd_pid_notifyf</refname> + <refname>sd_pid_notify_with_fds</refname> + <refpurpose>Notify service manager about start-up completion and other service status changes</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> + + <funcprototype> + <funcdef>int <function>sd_notify</function></funcdef> + <paramdef>int <parameter>unset_environment</parameter></paramdef> + <paramdef>const char *<parameter>state</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_notifyf</function></funcdef> + <paramdef>int <parameter>unset_environment</parameter></paramdef> + <paramdef>const char *<parameter>format</parameter></paramdef> + <paramdef>...</paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_pid_notify</function></funcdef> + <paramdef>pid_t <parameter>pid</parameter></paramdef> + <paramdef>int <parameter>unset_environment</parameter></paramdef> + <paramdef>const char *<parameter>state</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_pid_notifyf</function></funcdef> + <paramdef>pid_t <parameter>pid</parameter></paramdef> + <paramdef>int <parameter>unset_environment</parameter></paramdef> + <paramdef>const char *<parameter>format</parameter></paramdef> + <paramdef>...</paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_pid_notify_with_fds</function></funcdef> + <paramdef>pid_t <parameter>pid</parameter></paramdef> + <paramdef>int <parameter>unset_environment</parameter></paramdef> + <paramdef>const char *<parameter>state</parameter></paramdef> + <paramdef>const int *<parameter>fds</parameter></paramdef> + <paramdef>unsigned <parameter>n_fds</parameter></paramdef> + </funcprototype> + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + <para><function>sd_notify()</function> may be called by a service + to notify the service manager about state changes. It can be used + to send arbitrary information, encoded in an + environment-block-like string. Most importantly, it can be used for + start-up completion notification.</para> + + <para>If the <parameter>unset_environment</parameter> parameter is + non-zero, <function>sd_notify()</function> will unset the + <varname>$NOTIFY_SOCKET</varname> environment variable before + returning (regardless of whether the function call itself + succeeded or not). Further calls to + <function>sd_notify()</function> will then fail, but the variable + is no longer inherited by child processes.</para> + + <para>The <parameter>state</parameter> parameter should contain a + newline-separated list of variable assignments, similar in style + to an environment block. A trailing newline is implied if none is + specified. The string may contain any kind of variable + assignments, but the following shall be considered + well-known:</para> + + <variablelist> + <varlistentry> + <term>READY=1</term> + + <listitem><para>Tells the service manager that service startup + is finished. This is only used by systemd if the service + definition file has Type=notify set. Since there is little + value in signaling non-readiness, the only value services + should send is <literal>READY=1</literal> (i.e. + <literal>READY=0</literal> is not defined).</para></listitem> + </varlistentry> + + <varlistentry> + <term>RELOADING=1</term> + + <listitem><para>Tells the service manager that the service is + reloading its configuration. This is useful to allow the + service manager to track the service's internal state, and + present it to the user. Note that a service that sends this + notification must also send a <literal>READY=1</literal> + notification when it completed reloading its + configuration.</para></listitem> + </varlistentry> + + <varlistentry> + <term>STOPPING=1</term> + + <listitem><para>Tells the service manager that the service is + beginning its shutdown. This is useful to allow the service + manager to track the service's internal state, and present it + to the user.</para></listitem> + </varlistentry> + + <varlistentry> + <term>STATUS=...</term> + + <listitem><para>Passes a single-line UTF-8 status string back + to the service manager that describes the service state. This + is free-form and can be used for various purposes: general + state feedback, fsck-like programs could pass completion + percentages and failing programs could pass a human-readable + error message. Example: <literal>STATUS=Completed 66% of file + system check...</literal></para></listitem> + </varlistentry> + + <varlistentry> + <term>ERRNO=...</term> + + <listitem><para>If a service fails, the errno-style error + code, formatted as string. Example: <literal>ERRNO=2</literal> + for ENOENT.</para></listitem> + </varlistentry> + + <varlistentry> + <term>BUSERROR=...</term> + + <listitem><para>If a service fails, the D-Bus error-style + error code. Example: + <literal>BUSERROR=org.freedesktop.DBus.Error.TimedOut</literal></para></listitem> + </varlistentry> + + <varlistentry> + <term>MAINPID=...</term> + + <listitem><para>The main process ID (PID) of the service, in + case the service manager did not fork off the process itself. + Example: <literal>MAINPID=4711</literal></para></listitem> + </varlistentry> + + <varlistentry> + <term>WATCHDOG=1</term> + + <listitem><para>Tells the service manager to update the + watchdog timestamp. This is the keep-alive ping that services + need to issue in regular intervals if + <varname>WatchdogSec=</varname> is enabled for it. See + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for information how to enable this functionality and + <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> + for the details of how the service can check whether the + watchdog is enabled. </para></listitem> + </varlistentry> + + + <varlistentry> + <term>FDSTORE=1</term> + + <listitem><para>Stores additional file descriptors in the service manager. File + descriptors sent this way will be maintained per-service by the service manager + and will be passed again using the usual file descriptor passing logic on the next + invocation of the service, see + <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>. + This is useful for implementing service restart schemes where services serialize + their state to <filename>/run</filename>, push their file descriptors to the + system manager, and are then restarted, retrieving their state again via socket + passing and <filename>/run</filename>. Note that the service manager will accept + messages for a service only if <varname>FileDescriptorStoreMax=</varname> is set + to non-zero for it (defaults to zero, see + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>). + File descriptors must be pollable, see + <citerefentry><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>. + Multiple arrays of file descriptors may be sent in separate messages, in which + case the arrays are combined. Note that the service manager removes duplicate + file descriptors before passing them to the service. Use + <function>sd_pid_notify_with_fds()</function> to send messages with + <literal>FDSTORE=1</literal>, see below.</para></listitem> + </varlistentry> + + <varlistentry> + <term>FDNAME=...</term> + + <listitem><para>When used in combination with + <varname>FDSTORE=1</varname>, specifies a name for the + submitted file descriptors. This name is passed to the service + during activation, and may be queried using + <citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry>. File + descriptors submitted without this field set, will implicitly + get the name <literal>stored</literal> assigned. Note that, if + multiple file descriptors are submitted at once, the specified + name will be assigned to all of them. In order to assign + different names to submitted file descriptors, submit them in + separate invocations of + <function>sd_pid_notify_with_fds()</function>. The name may + consist of any ASCII character, but must not contain control + characters or <literal>:</literal>. It may not be longer than + 255 characters. If a submitted name does not follow these + restrictions, it is ignored.</para></listitem> + </varlistentry> + + <varlistentry> + <term>WATCHDOG_USEC=...</term> + + <listitem><para>Reset <varname>watchdog_usec</varname> value during runtime. + Notice that this is not available when using <function>sd_event_set_watchdog()</function> + or <function>sd_watchdog_enabled()</function>. + Example : <literal>WATCHDOG_USEC=20000000</literal></para></listitem> + </varlistentry> + + </variablelist> + + <para>It is recommended to prefix variable names that are not + listed above with <varname>X_</varname> to avoid namespace + clashes.</para> + + <para>Note that systemd will accept status data sent from a + service only if the <varname>NotifyAccess=</varname> option is + correctly set in the service definition file. See + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> + for details.</para> + + <para><function>sd_notifyf()</function> is similar to + <function>sd_notify()</function> but takes a + <function>printf()</function>-like format string plus + arguments.</para> + + <para><function>sd_pid_notify()</function> and + <function>sd_pid_notifyf()</function> are similar to + <function>sd_notify()</function> and + <function>sd_notifyf()</function> but take a process ID (PID) to + use as originating PID for the message as first argument. This is + useful to send notification messages on behalf of other processes, + provided the appropriate privileges are available. If the PID + argument is specified as 0, the process ID of the calling process + is used, in which case the calls are fully equivalent to + <function>sd_notify()</function> and + <function>sd_notifyf()</function>.</para> + + <para><function>sd_pid_notify_with_fds()</function> is similar to + <function>sd_pid_notify()</function> but takes an additional array + of file descriptors. These file descriptors are sent along the + notification message to the service manager. This is particularly + useful for sending <literal>FDSTORE=1</literal> messages, as + described above. The additional arguments are a pointer to the + file descriptor array plus the number of file descriptors in the + array. If the number of file descriptors is passed as 0, the call + is fully equivalent to <function>sd_pid_notify()</function>, i.e. + no file descriptors are passed. Note that sending file descriptors + to the service manager on messages that do not expect them (i.e. + without <literal>FDSTORE=1</literal>) they are immediately closed + on reception.</para> + </refsect1> + + <refsect1> + <title>Return Value</title> + + <para>On failure, these calls return a negative errno-style error + code. If <varname>$NOTIFY_SOCKET</varname> was not set and hence + no status data could be sent, 0 is returned. If the status was + sent, these functions return with a positive return value. In + order to support both, init systems that implement this scheme and + those which do not, it is generally recommended to ignore the + return value of this call.</para> + </refsect1> + + <refsect1> + <title>Notes</title> + + <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> + + <para>These functions send a single datagram with the + state string as payload to the <constant>AF_UNIX</constant> socket + referenced in the <varname>$NOTIFY_SOCKET</varname> environment + variable. If the first character of + <varname>$NOTIFY_SOCKET</varname> is <literal>@</literal>, the + string is understood as Linux abstract namespace socket. The + datagram is accompanied by the process credentials of the sending + service, using SCM_CREDENTIALS.</para> + </refsect1> + + <refsect1> + <title>Environment</title> + + <variablelist class='environment-variables'> + <varlistentry> + <term><varname>$NOTIFY_SOCKET</varname></term> + + <listitem><para>Set by the service manager for supervised + processes for status and start-up completion notification. + This environment variable specifies the socket + <function>sd_notify()</function> talks to. See above for + details.</para></listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Examples</title> + + <example> + <title>Start-up Notification</title> + + <para>When a service finished starting up, it might issue the + following call to notify the service manager:</para> + + <programlisting>sd_notify(0, "READY=1");</programlisting> + </example> + + <example> + <title>Extended Start-up Notification</title> + + <para>A service could send the following after completing + initialization:</para> + + <programlisting>sd_notifyf(0, "READY=1\n" + "STATUS=Processing requests...\n" + "MAINPID=%lu", + (unsigned long) getpid());</programlisting> + </example> + + <example> + <title>Error Cause Notification</title> + + <para>A service could send the following shortly before exiting, on failure:</para> + + <programlisting>sd_notifyf(0, "STATUS=Failed to start up: %s\n" + "ERRNO=%i", + strerror(errno), + errno);</programlisting> + </example> + + <example> + <title>Store a File Descriptor in the Service Manager</title> + + <para>To store an open file descriptor in the service manager, + in order to continue operation after a service restart without + losing state, use <literal>FDSTORE=1</literal>:</para> + + <programlisting>sd_pid_notify_with_fds(0, 0, "FDSTORE=1\nFDNAME=foobar", &fd, 1);</programlisting> + </example> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |