+
+ <para>If the exclamation mark is used, this
+ line is only safe of execute during boot, and
+ can break a running system. Lines without the
+ exclamation mark are presumed to be safe to
+ execute at any time, e.g. on package upgrades.
+ <command>systemd-tmpfiles</command> will
+ execute line with an exclamation mark only if
+ option <option>--boot</option> is given.
+ </para>
+
+ <para>For example:
+ <programlisting># Make sure these are created by default so that nobody else can
+d /tmp/.X11-unix 1777 root root 10d
+
+# Unlink the X11 lock files
+r! /tmp/.X[0-9]*-lock</programlisting>
+ The second line in contrast to the first one
+ would break a running system, and will only be
+ executed with <option>--boot</option>.</para>