man/environment.d.xml

   1 <?xml version="1.0"?>
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   3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1-or-later
   7
   8   Copyright © 2016 Red Hat, Inc.
   9 -->
  10 <refentry id="environment.d" conditional='ENABLE_ENVIRONMENT_D'
  11     xmlns:xi="http://www.w3.org/2001/XInclude">
  12
  13   <refentryinfo>
  14     <title>environment.d</title>
  15     <productname>systemd</productname>
  16   </refentryinfo>
  17
  18   <refmeta>
  19     <refentrytitle>environment.d</refentrytitle>
  20     <manvolnum>5</manvolnum>
  21   </refmeta>
  22
  23   <refnamediv>
  24     <refname>environment.d</refname>
  25     <refpurpose>Definition of user service environment</refpurpose>
  26   </refnamediv>
  27
  28   <refsynopsisdiv>
  29     <para><filename>~/.config/environment.d/*.conf</filename></para>
  30     <para><filename>/etc/environment.d/*.conf</filename></para>
  31     <para><filename>/run/environment.d/*.conf</filename></para>
  32     <para><filename>/usr/lib/environment.d/*.conf</filename></para>
  33     <para><filename>/etc/environment</filename></para>
  34   </refsynopsisdiv>
  35
  36   <refsect1>
  37     <title>Description</title>
  38
  39     <para>Configuration files in the <filename>environment.d/</filename> directories contain lists of
  40     environment variable assignments passed to services started by the systemd user instance.
  41     <citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  42     parses them and updates the environment exported by the systemd user instance. See below for an
  43     discussion of which processes inherit those variables.</para>
  44
  45     <para>It is recommended to use numerical prefixes for file names to simplify ordering.</para>
  46
  47     <para>For backwards compatibility, a symlink to <filename>/etc/environment</filename> is
  48     installed, so this file is also parsed.</para>
  49   </refsect1>
  50
  51   <xi:include href="standard-conf.xml" xpointer="confd" />
  52
  53   <refsect1>
  54     <title>Configuration Format</title>
  55
  56     <para>The configuration files contain a list of
  57     <literal><replaceable>KEY</replaceable>=<replaceable>VALUE</replaceable></literal> environment
  58     variable assignments, separated by newlines. The right hand side of these assignments may
  59     reference previously defined environment variables, using the <literal>${OTHER_KEY}</literal>
  60     and <literal>$OTHER_KEY</literal> format. It is also possible to use
  61     <literal>${<replaceable>FOO</replaceable>:-<replaceable>DEFAULT_VALUE</replaceable>}</literal>
  62     to expand in the same way as <literal>${<replaceable>FOO</replaceable>}</literal> unless the
  63     expansion would be empty, in which case it expands to <replaceable>DEFAULT_VALUE</replaceable>,
  64     and use
  65     <literal>${<replaceable>FOO</replaceable>:+<replaceable>ALTERNATE_VALUE</replaceable>}</literal>
  66     to expand to <replaceable>ALTERNATE_VALUE</replaceable> as long as
  67     <literal>${<replaceable>FOO</replaceable>}</literal> would have expanded to a non-empty value.
  68     No other elements of shell syntax are supported.</para>
  69
  70     <para>Each <replaceable>KEY</replaceable> must be a valid variable name. Empty lines
  71     and lines beginning with the comment character <literal>#</literal> are ignored.</para>
  72
  73     <refsect2>
  74       <title>Example</title>
  75       <example>
  76         <title>Setup environment to allow access to a program installed in
  77         <filename index="false">/opt/foo</filename></title>
  78
  79         <para><filename index="false">/etc/environment.d/60-foo.conf</filename>:
  80         </para>
  81         <programlisting>
  82         FOO_DEBUG=force-software-gl,log-verbose
  83         PATH=/opt/foo/bin:$PATH
  84         LD_LIBRARY_PATH=/opt/foo/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
  85         XDG_DATA_DIRS=/opt/foo/share:${XDG_DATA_DIRS:-/usr/local/share/:/usr/share/}
  86         </programlisting>
  87       </example>
  88     </refsect2>
  89   </refsect1>
  90
  91   <refsect1>
  92     <title>Applicability</title>
  93
  94     <para>Environment variables exported by the user service manager (<command>systemd --user</command>
  95     instance started in the <filename>user@<replaceable>uid</replaceable>.service</filename> system service)
  96     are passed to any services started by that service manager. In particular, this may include services
  97     which run user shells. For example in the GNOME environment, the graphical terminal emulator runs as the
  98     <filename>gnome-terminal-server.service</filename> user unit, which in turn runs the user shell, so that
  99     shell will inherit environment variables exported by the user manager. For other instances of the shell,
 100     not launched by the user service manager, the environment they inherit is defined by the program that
 101     starts them. Hint: in general,
 102     <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> units
 103     contain programs launched by systemd, and
 104     <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry> units
 105     contain programs launched by something else.</para>
 106
 107     <para>Note that these files do not affect the environment block of the service manager itself, but
 108     exclusively the environment blocks passed to the services it manages. Environment variables set that way
 109     thus cannot be used to influence behaviour of the service manager. In order to make changes to the
 110     service manager's environment block the environment must be modified before the user's service manager is
 111     invoked, for example from the system service manager or via a PAM module.</para>
 112
 113     <para>Specifically, for ssh logins, the
 114     <citerefentry project='die-net'><refentrytitle>sshd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 115     service builds an environment that is a combination of variables forwarded from the remote system and
 116     defined by <command>sshd</command>, see the discussion in
 117     <citerefentry project='die-net'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 118     A graphical display session will have an analogous mechanism to define the environment. Note that some
 119     managers query the systemd user instance for the exported environment and inject this configuration into
 120     programs they start, using <command>systemctl show-environment</command> or the underlying D-Bus call.
 121     </para>
 122   </refsect1>
 123
 124   <refsect1>
 125     <title>See Also</title>
 126     <para>
 127       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 128       <citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 129       <citerefentry><refentrytitle>systemd.environment-generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 130     </para>
 131   </refsect1>
 132
 133 </refentry>