title: journalctl - remove logs of a specific unit
body: <p>With journalctl, it is possible to remove the old logs, by specifying either the maximum disk space they can use, or the maximum age they can have, or the maximum number of separate journal files (using the options <code>--vacuum-size</code>, <code>--vacuum-time</code> or <code>--vacuum-files</code>).</p>
  
  <p>Is there a way to restrain this deletion to a specific systemd unit ?</p>
  
  <p><code>journalctl -u &lt;unit&gt; --vacuum-time=2d</code> seems not to work as desired: according to the documentation, <code>-u</code> only works when displaying logs.</p>