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With <para><filename>…</filename></para>, we get a separate "paragraph" for each line, i.e. entries separated by empty lines. This uses up a lot of space and was only done because docbook makes it hard to insert a newline. In some other places, <literallayout> was used, but then we cannot indent the source text (because the whitespace would end up in the final page). We can get the desired result with <simplelist>. With <simplelist> the items are indented in roff output, but not in html output. In some places this looks better then no indentation, and in others it would probably be better to have no indent. But this is a minor issue and we cannot control that. (I didn't convert all spots. There's a bunch of other man pages which have two lines, e.g. an executable and service file, and it doesn't matter there so much.)
135 lines
5.8 KiB
XML
135 lines
5.8 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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<!ENTITY % entities SYSTEM "custom-entities.ent" >
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%entities;
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]>
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd.environment-generator" conditional='ENABLE_ENVIRONMENT_D'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd.environment-generator</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd.environment-generator</refentrytitle>
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<manvolnum>7</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd.environment-generator</refname>
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<refpurpose>systemd environment file generators</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>&SYSTEM_ENV_GENERATOR_DIR;/some-generator</command>
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</cmdsynopsis>
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<cmdsynopsis>
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<command>&USER_ENV_GENERATOR_DIR;/some-generator</command>
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</cmdsynopsis>
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<para><simplelist>
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<member><filename>/run/systemd/system-environment-generators/*</filename></member>
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<member><filename>/etc/systemd/system-environment-generators/*</filename></member>
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<member><filename>/usr/local/lib/systemd/system-environment-generators/*</filename></member>
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<member><filename>&SYSTEM_ENV_GENERATOR_DIR;/*</filename></member>
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</simplelist></para>
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<para><simplelist>
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<member><filename>/run/systemd/user-environment-generators/*</filename></member>
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<member><filename>/etc/systemd/user-environment-generators/*</filename></member>
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<member><filename>/usr/local/lib/systemd/user-environment-generators/*</filename></member>
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<member><filename>&USER_ENV_GENERATOR_DIR;/*</filename></member>
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</simplelist></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>Generators are small executables that live in
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<filename>&SYSTEM_ENV_GENERATOR_DIR;/</filename> and other directories listed above.
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> will
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execute those binaries very early at the startup of each manager and at configuration
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reload time, before running the generators described in
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<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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and before starting any units. Environment generators can override the environment that the
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manager exports to services and other processes.</para>
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<para>Generators are loaded from a set of paths determined during compilation, as listed
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above. System and user environment generators are loaded from directories with names ending in
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<filename>system-environment-generators/</filename> and
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<filename>user-environment-generators/</filename>, respectively. Generators found in directories
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listed earlier override the ones with the same name in directories lower in the list. A symlink
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to <filename>/dev/null</filename> or an empty file can be used to mask a generator, thereby
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preventing it from running. Please note that the order of the two directories with the highest
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priority is reversed with respect to the unit load path, and generators in
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<filename>/run/</filename> overwrite those in <filename>/etc/</filename>.</para>
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<para>After installing new generators or updating the configuration, <command>systemctl
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daemon-reload</command> may be executed. This will re-run all generators, updating environment
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configuration. It will be used for any services that are started subsequently.</para>
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<para>Environment file generators are executed similarly to unit file generators described
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in
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<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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with the following differences:</para>
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<itemizedlist>
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<listitem>
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<para>Generators are executed sequentially in the alphanumerical order of the final
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component of their name. The output of each generator output is immediately parsed and used
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to update the environment for generators that run after that. Thus, later generators can use
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and/or modify the output of earlier generators.</para>
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</listitem>
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<listitem>
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<para>Generators are run by every manager instance, their output can be different for each
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user.</para>
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</listitem>
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</itemizedlist>
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<para>It is recommended to use numerical prefixes for generator names to simplify ordering.</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<example>
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<title>A simple generator that extends an environment variable if a directory exists in the file system</title>
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<programlisting># 50-xdg-data-dirs.sh
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<xi:include href="50-xdg-data-dirs.sh" parse="text" /></programlisting>
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</example>
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<example>
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<title>A more complicated generator which reads existing configuration and mutates one variable</title>
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<programlisting># 90-rearrange-path.py
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<xi:include href="90-rearrange-path.py" parse="text" /></programlisting>
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</example>
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<example>
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<title>Debugging a generator</title>
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<programlisting>SYSTEMD_LOG_LEVEL=debug VAR_A=something VAR_B="something else" \
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&SYSTEM_ENV_GENERATOR_DIR;/path-to-generator
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</programlisting>
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</example>
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</refsect1>
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<refsect1>
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<title>See also</title>
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<para>
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<citerefentry><refentrytitle>systemd-environment-d-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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