- <filename>/var/log/journal</filename>, if persistent storage is
- enabled. This call does not return until the operation is
- complete.</para></listitem>
+ <filename>/var/log/journal</filename>, if persistent storage
+ is enabled. This call does not return until the operation is
+ complete. Note that this call is idempotent: the data is only
+ flushed from <filename>/run/log/journal</filename> into
+ <filename>/var/log/journal</filename> once during system
+ runtime, and this command exits cleanly without executing any
+ operation if this has already has happened. This command
+ effectively guarantees that all data is flushed to
+ <filename>/var/log/journal</filename> at the time it
+ returns.</para></listitem>