man: document that ConditionKernelCommandLine= looks at /proc/1/environ in containers

Fixes: #16941

diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index f23c903d069efc59da09601bd114a2d53f8370db..27035798bc2bb46891521454a539b31baa412045 100644 (file)
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -1207,7 +1207,10 @@
           argument must either be a single word, or an assignment (i.e. two words, separated by
           <literal>=</literal>). In the former case the kernel command line is searched for the word
           appearing as is, or as left hand side of an assignment. In the latter case, the exact assignment is
-          looked for with right and left hand side matching.</para>
+          looked for with right and left hand side matching. This operates on the kernel command line
+          communicated to userspace via <filename>/proc/cmdline</filename>, except when the service manager
+          is invoked as payload of a container manager, in which case the command line of <filename>PID
+          1</filename> is used instead (i.e. <filename>/proc/1/cmdline</filename>).</para>
           </listitem>
         </varlistentry>