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man: document the new dash truncation drop-in directories

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Lennart Poettering 2018-02-23 20:42:57 +01:00
parent 7ce49e656b
commit 6c0a77953c
1 changed files with 17 additions and 8 deletions
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25
man/systemd.unit.xml
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@ -189,15 +189,24 @@
suffix is <filename>.requires/</filename> in this case.</para>
<para>Along with a unit file <filename>foo.service</filename>, a "drop-in" directory
<filename>foo.service.d/</filename> may exist. All files with the suffix
<literal>.conf</literal> from this directory will be parsed after the file itself is
parsed. This is useful to alter or add configuration settings for a unit, without having to
modify unit files. Each drop-in file must have appropriate section headers. Note that for
instantiated units, this logic will first look for the instance <literal>.d/</literal>
subdirectory and read its <literal>.conf</literal> files, followed by the template
<literal>.d/</literal> subdirectory and the <literal>.conf</literal> files there.</para>
<filename>foo.service.d/</filename> may exist. All files with the suffix <literal>.conf</literal> from this
directory will be parsed after the unit file itself is parsed. This is useful to alter or add configuration
settings for a unit, without having to modify unit files. Drop-in files must contain appropriate section
headers. For instantiated units, this logic will first look for the instance <literal>.d/</literal> subdirectory
(e.g. <literal>foo@bar.service.d/</literal>) and read its <literal>.conf</literal> files, followed by the template
<literal>.d/</literal> subdirectory (e.g. <literal>foo@.service.d/</literal>) and the <literal>.conf</literal>
files there. Moreover for units names containing dashes (<literal>-</literal>), the set of directories generated by
truncating the unit name after all dashes is searched too. Specifically, for a unit name
<filename>foo-bar-baz.service</filename> not only the the regular drop-in directory
<filename>foo-bar-baz.service.d/</filename> is searched but also both <filename>foo-bar-.service.d/</filename> and
<filename>foo-.service.d/</filename>. This is useful for defining common drop-ins for a set of related units, whose
names begin with a common prefix. This scheme is particularly useful for mount, automount and slice units, whose
systematic naming structure is built around dashes as component separators. Note that equally named drop-in files
further down the prefix hierarchy override those further up,
i.e. <filename>foo-bar-.service.d/10-override.conf</filename> overrides
<filename>foo-.service.d/10-override.conf</filename>.</para>
<para>In addition to <filename>/etc/systemd/system</filename>, the drop-in <literal>.d</literal>
<para>In addition to <filename>/etc/systemd/system</filename>, the drop-in <literal>.d/</literal>
directories for system services can be placed in <filename>/usr/lib/systemd/system</filename> or
<filename>/run/systemd/system</filename> directories. Drop-in files in <filename>/etc</filename>
take precedence over those in <filename>/run</filename> which in turn take precedence over those