Add SPDX license identifiers to man pages

[thirdparty/systemd.git] / man / systemd-notify.xml

diff --git a/man/systemd-notify.xml b/man/systemd-notify.xml
index 4a8e119eb6fb174b0a11642d3abfe2ac13d5bc7c..acd4ee41fc528978027b9763e0300a4b2e54af52 100644 (file)
--- a/man/systemd-notify.xml
+++ b/man/systemd-notify.xml
@@ -3,6 +3,8 @@
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
 
 <!--
+  SPDX-License-Identifier: LGPL-2.1+
+
   This file is part of systemd.
 
   Copyright 2010 Lennart Poettering
@@ -72,10 +74,24 @@
     <para>The command line may carry a list of environment variables
     to send as part of the status update.</para>
 
-    <para>Note that systemd will refuse reception of status updates
-    from this command unless <varname>NotifyAccess=all</varname> is
-    set for the service unit this command is called from.</para>
-
+    <para>Note that systemd will refuse reception of status updates from this command unless
+    <varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
+
+    <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
+    the sending process is still around at the time PID 1 processes the message, or if the sending process is
+    explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
+    off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
+    <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
+    <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
+    attribute the message to the unit, and thus will ignore it, even if
+    <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
+
+    <para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
+    have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
+    it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
+    invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
+    sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
+    limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
   </refsect1>
 
   <refsect1>