man: add systemd.environment-generator(7) with two examples
v2: - add example files to EXTRA_DIST v3: - rework for the new scheme where nothing is written to disk v4: - use separate dirs for system and user env generators
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
parent
64691d2024
commit
1bd2d4e31b
|
|
@ -146,6 +146,7 @@ MANPAGES += \
|
|||
man/systemd.1 \
|
||||
man/systemd.automount.5 \
|
||||
man/systemd.device.5 \
|
||||
man/systemd.environment-generator.7 \
|
||||
man/systemd.exec.5 \
|
||||
man/systemd.generator.7 \
|
||||
man/systemd.journal-fields.7 \
|
||||
|
|
@ -2827,6 +2828,7 @@ EXTRA_DIST += \
|
|||
man/systemd-volatile-root.service.xml \
|
||||
man/systemd.automount.xml \
|
||||
man/systemd.device.xml \
|
||||
man/systemd.environment-generator.xml \
|
||||
man/systemd.exec.xml \
|
||||
man/systemd.generator.xml \
|
||||
man/systemd.journal-fields.xml \
|
||||
|
|
|
|||
|
|
@ -765,7 +765,9 @@ EXTRA_DIST += \
|
|||
tools/make-man-rules.py \
|
||||
tools/make-directive-index.py \
|
||||
tools/xml_helper.py \
|
||||
man/glib-event-glue.c
|
||||
man/glib-event-glue.c \
|
||||
man/50-xdg-data-dirs.sh \
|
||||
man/90-rearrange-path.py
|
||||
|
||||
# ------------------------------------------------------------------------------
|
||||
noinst_LTLIBRARIES += \
|
||||
|
|
|
|||
|
|
@ -0,0 +1,12 @@
|
|||
#!/bin/bash
|
||||
|
||||
# set the default value
|
||||
XDG_DATA_DIRS="${XDG_DATA_DIRS:-/usr/local/share/:/usr/share}"
|
||||
|
||||
# add a directory if it exists
|
||||
if [[ -d /opt/foo/share ]]; then
|
||||
XDG_DATA_DIRS=/opt/foo/share:${XDG_DATA_DIRS}
|
||||
fi
|
||||
|
||||
# write our output
|
||||
echo XDG_DATA_DIRS=$XDG_DATA_DIRS
|
||||
|
|
@ -0,0 +1,40 @@
|
|||
#!/usr/bin/python3
|
||||
|
||||
"""
|
||||
|
||||
Proof-of-concept systemd environment generator that makes sure that bin dirs
|
||||
are always after matching sbin dirs in the path.
|
||||
(Changes /sbin:/bin:/foo/bar to /bin:/sbin:/foo/bar.)
|
||||
|
||||
This generator shows how to override the configuration possibly created by
|
||||
earlier generators. It would be easier to write in bash, but let's have it
|
||||
in Python just to prove that we can, and to serve as a template for more
|
||||
interesting generators.
|
||||
|
||||
"""
|
||||
|
||||
import os
|
||||
import pathlib
|
||||
|
||||
def rearrange_bin_sbin(path):
|
||||
"""Make sure any pair of …/bin, …/sbin directories is in this order
|
||||
|
||||
>>> rearrange_bin_sbin('/bin:/sbin:/usr/sbin:/usr/bin')
|
||||
'/bin:/sbin:/usr/bin:/usr/sbin'
|
||||
"""
|
||||
items = [pathlib.Path(p) for p in path.split(':')]
|
||||
for i in range(len(items)):
|
||||
if 'sbin' in items[i].parts:
|
||||
ind = items[i].parts.index('sbin')
|
||||
bin = pathlib.Path(*items[i].parts[:ind], 'bin', *items[i].parts[ind+1:])
|
||||
if bin in items[i+1:]:
|
||||
j = i + 1 + items[i+1:].index(bin)
|
||||
items[i], items[j] = items[j], items[i]
|
||||
return ':'.join(p.as_posix() for p in items)
|
||||
|
||||
if __name__ == '__main__':
|
||||
path = os.environ['PATH'] # This should be always set.
|
||||
# If it's not, we'll just crash, we is OK too.
|
||||
new = rearrange_bin_sbin(path)
|
||||
if new != path:
|
||||
print('PATH={}'.format(new))
|
||||
|
|
@ -0,0 +1,159 @@
|
|||
<?xml version='1.0'?> <!--*-nxml-*-->
|
||||
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
|
||||
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
|
||||
<!ENTITY % entities SYSTEM "custom-entities.ent" >
|
||||
%entities;
|
||||
]>
|
||||
|
||||
<!--
|
||||
This file is part of systemd.
|
||||
|
||||
Copyright 2017 Zbigniew Jędrzejewski-Szmek
|
||||
|
||||
systemd is free software; you can redistribute it and/or modify it
|
||||
under the terms of the GNU Lesser General Public License as published by
|
||||
the Free Software Foundation; either version 2.1 of the License, or
|
||||
(at your option) any later version.
|
||||
|
||||
systemd is distributed in the hope that it will be useful, but
|
||||
WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||||
Lesser General Public License for more details.
|
||||
|
||||
You should have received a copy of the GNU Lesser General Public License
|
||||
along with systemd; If not, see <http://www.gnu.org/licenses/>.
|
||||
-->
|
||||
|
||||
<refentry id="systemd.environment-generator" xmlns:xi="http://www.w3.org/2001/XInclude">
|
||||
<refentryinfo>
|
||||
<title>systemd.environment-generator</title>
|
||||
<productname>systemd</productname>
|
||||
|
||||
<authorgroup>
|
||||
<author>
|
||||
<contrib>Developer</contrib>
|
||||
<firstname>Zbigniew</firstname>
|
||||
<surname>Jędrzejewski-Szmek</surname>
|
||||
<email>zbyszek@in.waw.pl</email>
|
||||
</author>
|
||||
</authorgroup>
|
||||
</refentryinfo>
|
||||
|
||||
<refmeta>
|
||||
<refentrytitle>systemd.environment-generator</refentrytitle>
|
||||
<manvolnum>7</manvolnum>
|
||||
</refmeta>
|
||||
|
||||
<refnamediv>
|
||||
<refname>systemd.environment-generator</refname>
|
||||
<refpurpose>Systemd environment file generators</refpurpose>
|
||||
</refnamediv>
|
||||
|
||||
<refsynopsisdiv>
|
||||
<cmdsynopsis>
|
||||
<command>&systemenvgeneratordir;/some-generator</command>
|
||||
</cmdsynopsis>
|
||||
<cmdsynopsis>
|
||||
<command>&userenvgeneratordir;/some-generator</command>
|
||||
</cmdsynopsis>
|
||||
|
||||
<para>
|
||||
<literallayout><filename>/run/systemd/system-environment-generators/*</filename>
|
||||
<filename>/etc/systemd/system-environment-generators/*</filename>
|
||||
<filename>/usr/local/lib/systemd/system-environment-generators/*</filename>
|
||||
<filename>&systemenvgeneratordir;/*</filename></literallayout>
|
||||
</para>
|
||||
|
||||
<para>
|
||||
<literallayout><filename>/run/systemd/user-environment-generators/*</filename>
|
||||
<filename>/etc/systemd/user-environment-generators/*</filename>
|
||||
<filename>/usr/local/lib/systemd/user-environment-generators/*</filename>
|
||||
<filename>&userenvgeneratordir;/*</filename></literallayout>
|
||||
</para>
|
||||
</refsynopsisdiv>
|
||||
|
||||
<refsect1>
|
||||
<title>Description</title>
|
||||
<para>Generators are small executables that live in
|
||||
<filename>&systemenvgeneratordir;/</filename> and other directories listed above.
|
||||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> will
|
||||
execute those binaries very early at the startup of each manager and at configuration
|
||||
reload time, before running the generators described in
|
||||
<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
||||
and before starting any units. Environment generators can override the environment that the
|
||||
manager exports to services and other processes.</para>
|
||||
|
||||
<para>Generators are loaded from a set of paths determined during compilation, as listed
|
||||
above. System and user environment generators are loaded from directories with names ending in
|
||||
<filename>system-environment-generators/</filename> and
|
||||
<filename>user-environment-generators/</filename>, respectively. Generators found in directories
|
||||
listed earlier override the ones with the same name in directories lower in the list. A symlink
|
||||
to <filename>/dev/null</filename> or an empty file can be used to mask a generator, thereby
|
||||
preventing it from running. Please note that the order of the two directories with the highest
|
||||
priority is reversed with respect to the unit load path, and generators in
|
||||
<filename>/run</filename> overwrite those in <filename>/etc</filename>.</para>
|
||||
|
||||
<para>After installing new generators or updating the configuration, <command>systemctl
|
||||
daemon-reload</command> may be executed. This will re-run all generators, updating environment
|
||||
configuration. It will be used for any services that are started subsequently.</para>
|
||||
|
||||
<para>Environment file generators are executed similarly to unit file generators described
|
||||
in
|
||||
<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
||||
with the following differences:</para>
|
||||
|
||||
<itemizedlist>
|
||||
<listitem>
|
||||
<para>Generators are executed sequentially in the alphanumerical order of the final
|
||||
component of their name. The output of each generator output is immediately parsed and used
|
||||
to update the environment for generators that run after that. Thus, later generators can use
|
||||
and/or modify the output of earlier generators.</para>
|
||||
</listitem>
|
||||
|
||||
<listitem>
|
||||
<para>Generators are run by every manager instance, their output can be different for each
|
||||
user.</para>
|
||||
</listitem>
|
||||
</itemizedlist>
|
||||
|
||||
<para>It is recommended to use numerical prefixes for generator names to simplify ordering.</para>
|
||||
</refsect1>
|
||||
|
||||
<refsect1>
|
||||
<title>Examples</title>
|
||||
|
||||
<example>
|
||||
<title>A simple generator that extends an environment variable if a directory exists in the file system</title>
|
||||
|
||||
<programlisting># 50-xdg-data-dirs.sh
|
||||
|
||||
<xi:include href="50-xdg-data-dirs.sh" parse="text" /></programlisting>
|
||||
</example>
|
||||
|
||||
<example>
|
||||
<title>A more complicated generator which reads existing configuration and mutates one variable</title>
|
||||
|
||||
<programlisting># 90-rearrange-path.py
|
||||
|
||||
<xi:include href="90-rearrange-path.py" parse="text" /></programlisting>
|
||||
</example>
|
||||
|
||||
<example>
|
||||
<title>Debugging a generator</title>
|
||||
|
||||
<programlisting>SYSTEMD_LOG_LEVEL=debug VAR_A=something VAR_B="something else" \
|
||||
&systemenvgeneratordir;/path-to-generator
|
||||
</programlisting>
|
||||
</example>
|
||||
</refsect1>
|
||||
|
||||
<refsect1>
|
||||
<title>See also</title>
|
||||
|
||||
<para>
|
||||
<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
|
||||
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||||
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
||||
</para>
|
||||
</refsect1>
|
||||
</refentry>
|
||||
|
|
@ -342,7 +342,8 @@ find $dir</programlisting>
|
|||
<citerefentry><refentrytitle>systemd-system-update-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
||||
<citerefentry><refentrytitle>systemd-sysv-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
|
||||
<citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
|
||||
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
||||
<citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
||||
<citerefentry><refentrytitle>systemd.environment-generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>
|
||||
</para>
|
||||
</refsect1>
|
||||
</refentry>
|
||||
|
|
|
|||
Loading…
Reference in New Issue