-<p>
- A message like "Cannot lock down memory" in the output from JACK as
- it starts up. This output may be "hidden" in the Messages window of
- QJackctrl (aka JACK Control), so you should check there.
-</p>
+<h3>What is the problem?</h3>
+ <p>
+ To function as intended, JACK needs to run with access to two
+ operating system facilities called <dfn>realtime scheduling</dfn> and
+ <dfn>memory locking</dfn>. This means that you, the user who starts JACK, must be
+ allowed access to these facilities. By default, Ubuntu does create a
+ user group that has this permission but — it does not put new
+ users into this group by default. Read more about why <a href="https://wiki.ubuntu.com/Audio/TheAudioGroup">here</a>.
+ Consequently, you will not have permission to run JACK in the way you should.
+ </p>
+<h3>Symptoms</h3>
+ <p>
+ A message like <samp>Cannot lock down memory</samp> in the output from JACK as
+ it starts up. This output may be hidden in the Messages window of
+ QJackctrl (aka JACK Control), so you should check there.
+ </p>