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man/environment.d.xml
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dongshengyuan
man: document that $XDG_CONFIG_HOME affects environment.d lookup path
30 июн 2026, 10:00
30 июн 2026, 10:00b0d48e0
<?xml version="1.0"?>
<!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!--
  SPDX-License-Identifier: LGPL-2.1-or-later

  Copyright © 2016 Red Hat, Inc.
-->
<refentry id="environment.d" conditional='ENABLE_ENVIRONMENT_D'
    xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>environment.d</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>environment.d</refentrytitle>
    <manvolnum>5</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>environment.d</refname>
    <refpurpose>Definition of user service environment</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><simplelist>
      <member><filename>~/.config/environment.d/*.conf</filename></member>
      <member><filename>/etc/environment.d/*.conf</filename></member>
      <member><filename>/run/environment.d/*.conf</filename></member>
      <member><filename>/usr/local/lib/environment.d/*.conf</filename></member>
      <member><filename>/usr/lib/environment.d/*.conf</filename></member>
      <member><filename>/etc/environment</filename></member>
    </simplelist></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>Configuration files in the <filename>environment.d/</filename> directories contain lists of
    environment variable assignments passed to services started by the systemd user instance.
    <citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    parses them and updates the environment exported by the systemd user instance. See below for an
    discussion of which processes inherit those variables.</para>

    <para>The user-level configuration directory defaults to <filename>~/.config/environment.d/</filename>.
    If <varname>$XDG_CONFIG_HOME</varname> is set to an absolute path in the user service manager
    environment (e.g. via PAM or <filename>/etc/environment</filename>), it takes precedence over
    <filename>~/.config/</filename>. Note that this creates a bootstrapping consideration: variables
    set in <filename>environment.d/</filename> files, including <varname>$XDG_CONFIG_HOME</varname>
    itself, are not available when the generator determines which directory to read.</para>

    <para>It is recommended to use numerical prefixes for file names to simplify ordering.</para>

    <para>For backwards compatibility, a symlink to <filename>/etc/environment</filename> is
    installed, so this file is also parsed.</para>
  </refsect1>

  <xi:include href="standard-conf.xml" xpointer="confd" />

  <refsect1>
    <title>Configuration Format</title>

    <para>The configuration files contain a list of
    <literal><replaceable>KEY</replaceable>=<replaceable>VALUE</replaceable></literal> environment
    variable assignments, separated by newlines. The right hand side of these assignments may
    reference previously defined environment variables, using the <literal>${OTHER_KEY}</literal>
    and <literal>$OTHER_KEY</literal> format. It is also possible to use
    <literal>${<replaceable>FOO</replaceable>:-<replaceable>DEFAULT_VALUE</replaceable>}</literal>
    to expand in the same way as <literal>${<replaceable>FOO</replaceable>}</literal> unless the
    expansion would be empty, in which case it expands to <replaceable>DEFAULT_VALUE</replaceable>,
    and use
    <literal>${<replaceable>FOO</replaceable>:+<replaceable>ALTERNATE_VALUE</replaceable>}</literal>
    to expand to <replaceable>ALTERNATE_VALUE</replaceable> as long as
    <literal>${<replaceable>FOO</replaceable>}</literal> would have expanded to a non-empty value.
    You can escape a literal dollar sign <literal>$</literal> by doubling it, as in
    <literal>$$</literal>.</para>

    <para>A backslash character <literal>\</literal> followed by a newline acts as a line
    continuation (both characters are discarded); in all other cases, the backslash is consumed and
    the following character is included literally in the value. This can be used to preserve
    leading/trailing whitespace or include literal backslashes.</para>

    <para>You may optionally enclose the right hand side of assignments in pairs of either
    <constant>'</constant>single quotes<constant>'</constant> or <constant>"</constant>double
    quotes<constant>"</constant>; these will be stripped from the value before saving it. Using
    either quoting style does not affect variable expansion; however, single quotes disable
    backslash escaping entirely, while double quoting removes backslashes that precede double quotes
    <literal>"</literal>, dollar signs <literal>$</literal>, backslashes <literal>\</literal>,
    backticks <literal>`</literal>, and newlines, and leaves all other backslashes in place.</para>

    <para>Leading and trailing whitespace characters are stripped from both the left and right hand
    sides of the assignment. To preserve such spaces in the value, you can either enclose the entire
    value in quotes, or escape the space characters with backslashes. You can also include literal
    newlines in the value by enclosing it in quotes.</para>

    <para>Each <replaceable>KEY</replaceable> must be a valid variable name. Empty lines and lines
    beginning with the comment characters <literal>#</literal> or <literal>;</literal> are ignored.
    No other elements of shell syntax are supported.</para>

    <refsect2>
      <title>Examples</title>
      <example>
        <title>Setup environment to allow access to a program installed in
        <filename index="false">/opt/foo</filename></title>

        <para><filename index="false">/etc/environment.d/60-foo.conf</filename>:
        </para>
        <programlisting>
FOO_DEBUG=force-software-gl,log-verbose
PATH=/opt/foo/bin:$PATH
LD_LIBRARY_PATH=/opt/foo/lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
XDG_DATA_DIRS=/opt/foo/share:${XDG_DATA_DIRS:-/usr/local/share/:/usr/share/}
</programlisting>
      </example>

      <example>
        <title>Escaping and variable expansion</title>

        <para><filename index="false">/etc/environment.d/70-bar.conf</filename>:
        </para>
        <programlisting>
# A comment
test_var=(variable)
; Another comment
test_comment=value # This is a part of the variable, and not a comment!

test_none= \ before\
after "" '' \${test_var}
test_double=" \ before\
after "" '' \${test_var}"
test_single=' \ before\
after "" '' \${test_var}'

# The above example produces the following environment variables, written using
# C-style string escapes:
#
# test_var="(variable)"
# test_comment="value # This is a part of the variable, and not a comment!"
# test_none=" beforeafter \"\" '' (variable)"
# test_double=" \\ beforeafter  '' (variable)"
# test_single=" \\ before\\\nafter \"\"  \\(variable)"
</programlisting>
      </example>
    </refsect2>
  </refsect1>

  <refsect1>
    <title>Applicability</title>

    <para>Environment variables exported by the user service manager (<command>systemd --user</command>
    instance started in the <filename>user@<replaceable>uid</replaceable>.service</filename> system service)
    are passed to any services started by that service manager. In particular, this may include services
    which run user shells. For example in the GNOME environment, the graphical terminal emulator runs as the
    <filename>gnome-terminal-server.service</filename> user unit, which in turn runs the user shell, so that
    shell will inherit environment variables exported by the user manager. For other instances of the shell,
    not launched by the user service manager, the environment they inherit is defined by the program that
    starts them. Hint: in general,
    <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> units
    contain programs launched by systemd, and
    <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry> units
    contain programs launched by something else.</para>

    <para>Note that these files do not affect the environment block of the service manager itself, but
    exclusively the environment blocks passed to the services it manages. Environment variables set that way
    thus cannot be used to influence behaviour of the service manager. In order to make changes to the
    service manager's environment block the environment must be modified before the user's service manager is
    invoked, for example from the system service manager or via a PAM module.</para>

    <para>Specifically, for ssh logins, the
    <citerefentry project='man-pages'><refentrytitle>sshd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    service builds an environment that is a combination of variables forwarded from the remote system and
    defined by <command>sshd</command>, see the discussion in
    <citerefentry project='man-pages'><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
    A graphical display session will have an analogous mechanism to define the environment. Note that some
    managers query the systemd user instance for the exported environment and inject this configuration into
    programs they start, using <command>systemctl show-environment</command> or the underlying D-Bus call.
    </para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para><simplelist type="inline">
      <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>systemd.environment-generator</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
    </simplelist></para>
  </refsect1>

</refentry>