man: Add a note about what environment variables are available by default

[elogind.git] / man / systemd.exec.xml

diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index b761832ed6bbdca94debe5df33cdb579d4c0376f..ff8b812ef44087ab47278cde43bcc83e3614952a 100644 (file)
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -1,4 +1,3 @@
-<?xml version='1.0'?> <!--*-nxml-*-->
 <?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
@@ -77,6 +76,27 @@
                 configuration options are configured in the [Service],
                 [Socket], [Mount], or [Swap] sections, depending on the unit
                 type.</para>
+
+                <para>Processes started by the system systemd instance
+                are executed in a clean environment in which only the
+                <varname>$PATH</varname> and <varname>$LANG</varname>
+                variables are set by default. In order to add
+                additional variables, see the
+                <varname>Environment=</varname> and
+                <varname>EnvironmentFile=</varname> options below. To
+                specify variables globally, see
+                <varname>DefaultEnvironment=</varname> in
+                <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                or the kernel option
+                <varname>systemd.setenv=</varname> in
+                <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>. Processes
+                started by the user systemd instances inherit all
+                environment variables from the user systemd instance,
+                and have <varname>$HOME</varname>,
+                <varname>$USER</varname>,
+                <varname>$XDG_RUNTIME_DIR</varname> defined, among
+                others. In addition, <varname>$MANAGERPID</varname>
+                contains the PID of the user systemd instance.</para>
         </refsect1>
 
         <refsect1>
@@ -327,8 +347,8 @@
                                 absolute filename or wildcard
                                 expression, optionally prefixed with
                                 <literal>-</literal>, which indicates
-                                that if the file does not exist it
-                                won't be read and no error or warning
+                                that if the file does not exist, it
+                                will not be read and no error or warning
                                 message is logged.  This option may be
                                 specified more than once in which case
                                 all specified files are read. If the
@@ -835,7 +855,7 @@
                                 <varname>InaccessibleDirectories=</varname>
                                 may be prefixed with
                                 <literal>-</literal>, in which case
-                                they will be ignored when they don't
+                                they will be ignored when they do not
                                 exist.</para></listitem>
                         </varlistentry>
 
@@ -972,7 +992,7 @@
                                 <function>sigreturn</function>,
                                 <function>exit_group</function>,
                                 <function>exit</function> system calls
-                                are implicitly whitelisted and don't
+                                are implicitly whitelisted and do not
                                 need to be listed explicitly. This
                                 option may be specified more than once
                                 in which case the filter masks are