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6  SPDX-License-Identifier: LGPL-2.1-or-later
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8  Copyright © 2016 Red Hat, Inc.
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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 for 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 manager (<command>systemd --user</command> instance
95    started in the <filename>user@<replaceable>uid</replaceable>.service</filename> system service) apply to
96    any services started by that manager. In particular, this may include services which run user shells. For
97    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 manager, the environment they inherit is defined by the program that starts
101    them. Hint: in general,
102    <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
103    units contain programs launched by systemd, and
104    <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>
105    units contain programs launched by something else.</para>
106
107    <para>Specifically, for ssh logins, the
108    <citerefentry project='die-net'><refentrytitle>sshd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
109    service builds an environment that is a combination of variables forwarded from the remote system and
110    defined by <command>sshd</command>, see the discussion in
111    <citerefentry project='die-net'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
112    A graphical display session will have an analogous mechanism to define the environment. Note that some
113    managers query the systemd user instance for the exported environment and inject this configuration into
114    programs they start, using <command>systemctl show-environment</command> or the underlying D-Bus call.
115    </para>
116  </refsect1>
117
118  <refsect1>
119    <title>See Also</title>
120    <para>
121      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
122      <citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
123      <citerefentry><refentrytitle>systemd.environment-generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>
124    </para>
125  </refsect1>
126
127</refentry>
128