with SysV</ulink> document.</para>
</refsect1>
+ <refsect1>
+ <title>Service Templates</title>
+
+ <para>It is possible for <command>systemd</command> services to take a single argument via the
+ <literal><replaceable>service</replaceable>@<replaceable>argument</replaceable>.service</literal>
+ syntax. Such services are called "instantiated" services, while the unit definition without the
+ <replaceable>argument</replaceable> parameter is called a "template". An example could be a
+ <filename>dhcpcd@.service</filename> service template which takes a network interface as a
+ parameter to form an instantiated service. Within the service file, this parameter or "instance
+ name" can be accessed with %-specifiers. See
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for details.</para>
+ </refsect1>
+
<refsect1>
<title>Implicit Dependencies</title>
<para>Unit files are loaded from a set of paths determined during
compilation, described in the next section.</para>
+ <para>Unit files can be parameterized by a single argument called the "instance name". The unit
+ is then constructed based on a "template file" which serves as the definition of multiple
+ services or other units. A template unit must have a single <literal>@</literal> at the end of
+ the name (right before the type suffix). The name of the full unit is formed by inserting the
+ instance name between <literal>@</literal> and the unit type suffix. In the unit file itself,
+ the instance parameter may be referred to using <literal>%i</literal> and other specifiers, see
+ below.</para>
+
<para>Unit files may contain additional options on top of those
listed here. If systemd encounters an unknown option, it will
write a warning log message but continue loading the unit. If an
socket-based activation which make dependencies implicit,
resulting in a both simpler and more flexible system.</para>
- <para>Optionally, units may be instantiated from a
- template file at runtime. This allows creation of
- multiple units from a single configuration file. If
- systemd looks for a unit configuration file, it will
- first search for the literal unit name in the
- file system. If that yields no success and the unit
- name contains an <literal>@</literal> character, systemd will look for a
- unit template that shares the same name but with the
- instance string (i.e. the part between the <literal>@</literal> character
- and the suffix) removed. Example: if a service
- <filename>getty@tty3.service</filename> is requested
- and no file by that name is found, systemd will look
- for <filename>getty@.service</filename> and
- instantiate a service from that configuration file if
- it is found.</para>
+ <para>As mentioned above, a unit may be instantiated from a template file. This allows creation
+ of multiple units from a single configuration file. If systemd looks for a unit configuration
+ file, it will first search for the literal unit name in the file system. If that yields no
+ success and the unit name contains an <literal>@</literal> character, systemd will look for a
+ unit template that shares the same name but with the instance string (i.e. the part between the
+ <literal>@</literal> character and the suffix) removed. Example: if a service
+ <filename>getty@tty3.service</filename> is requested and no file by that name is found, systemd
+ will look for <filename>getty@.service</filename> and instantiate a service from that
+ configuration file if it is found.</para>
<para>To refer to the instance string from within the
configuration file you may use the special <literal>%i</literal>