man: restore description of ConditionControlGroupController=v1|v2

We use ConditionControlGroupController=v2 in systemd-oomd.service, and also
this condition makes sense in general, so it should be documented.

This reverts a part of 6d48c7cf736ced70c1c2fef1e1f03618911d04bc.

Deprecated commandline options and v1 controller names were removed from
the description.

diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index 9411ea2e0387153de85c5ded0198c4d8fbc7ed0b..c618e403f71ed8b9a62de7f71af33316174ad7ff 100644 (file)
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -1602,14 +1602,23 @@
           <term><varname>ConditionControlGroupController=</varname></term>
 
           <listitem><para>Check whether given cgroup controllers (e.g. <literal>cpu</literal>) are available
-          for use on the system.</para>
+          for use on the system or whether the legacy v1 cgroup or the modern v2 cgroup hierarchy is used.
+          </para>
 
           <para>Multiple controllers may be passed with a space separating them; in this case the condition
           will only pass if all listed controllers are available for use. Controllers unknown to systemd are
-          ignored. Valid controllers are <literal>cpu</literal>, <literal>cpuset</literal>,
-          <literal>io</literal>, <literal>memory</literal>, and <literal>pids</literal>. Even if available in
-          the kernel, a particular controller may not be available if it was disabled on the kernel command
-          line with <varname>cgroup_disable=controller</varname>.</para></listitem>
+          ignored. Valid controllers are <literal>cpu</literal>, <literal>io</literal>,
+          <literal>memory</literal>, and <literal>pids</literal>. Even if available in the kernel, a
+          particular controller may not be available if it was disabled on the kernel command line with
+          <varname>cgroup_disable=controller</varname>.</para>
+
+          <para>Alternatively, two special strings <literal>v1</literal> and <literal>v2</literal> may be
+          specified (without any controller names). <literal>v2</literal> will pass if the unified v2 cgroup
+          hierarchy is used, and <literal>v1</literal> will pass if the legacy v1 hierarchy or the hybrid
+          hierarchy are used. Note that legacy or hybrid hierarchies have been deprecated. See
+          <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
+          more information.</para>
+          </listitem>
         </varlistentry>
 
         <varlistentry>