systemd/man/environment.d.xml

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<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><filename>~/.config/environment.d/*.conf</filename></para>
    <para><filename>/etc/environment.d/*.conf</filename></para>
    <para><filename>/run/environment.d/*.conf</filename></para>
    <para><filename>/usr/lib/environment.d/*.conf</filename></para>
    <para><filename>/etc/environment</filename></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>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.
    No other elements of shell syntax are supported.</para>

    <para>Each <replaceable>KEY</replaceable> must be a valid variable name. Empty lines
    and lines beginning with the comment character <literal>#</literal> are ignored.</para>

    <refsect2>
      <title>Example</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>
    </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='die-net'><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='die-net'><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>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.environment-generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>