contents/getting-started/tracing-the-linux-kernel.md

   1 ---
   2 id: tracing-the-linux-kernel
   3 ---
   4
   5 Make sure LTTng-tools and LTTng-modules packages
   6 [are installed](#doc-installing-lttng).
   7
   8 Since you're about to trace the Linux kernel itself, let's look at the
   9 available kernel events using the `lttng` tool, which has a
  10 Git-like command line structure:
  11
  12 <pre class="term">
  13 lttng list --kernel
  14 </pre>
  15
  16 Before tracing, you need to create a session:
  17
  18 <pre class="term">
  19 sudo lttng create my-session
  20 </pre>
  21
  22 <div class="tip">
  23 <p>
  24     <span class="t">Tip:</span>You can avoid using <code>sudo</code> in
  25     the previous and following commands if your user is a member of the
  26     <a href="/docs/#doc-lttng-sessiond" class="int"><code>tracing</code>
  27     group</a>.
  28 </p>
  29 </div>
  30
  31 `my-session` is the tracing session name and could be anything you
  32 like. `auto` is used if omitted.
  33
  34 Let's now enable some events for this session:
  35
  36 <pre class="term">
  37 sudo lttng enable-event --kernel sched_switch,sched_process_fork
  38 </pre>
  39
  40 or you might want to simply enable all available kernel events (beware
  41 that trace files grow rapidly when doing this):
  42
  43 <pre class="term">
  44 sudo lttng enable-event --kernel --all
  45 </pre>
  46
  47 Start tracing:
  48
  49 <pre class="term">
  50 sudo lttng start
  51 </pre>
  52
  53 By default, traces are saved in
  54 <code>~/lttng-traces/<em>name</em>-<em>date</em>-<em>time</em></code>,
  55 where <code><em>name</em></code> is the session name.
  56
  57 When you're done tracing:
  58
  59 <pre class="term">
  60 sudo lttng stop
  61 sudo lttng destroy
  62 </pre>
  63
  64 Although `destroy` looks scary here, it doesn't actually destroy the
  65 outputted trace files: it only destroys the tracing session.
  66
  67 What's next? Have a look at
  68 [Viewing and analyzing your traces](#doc-viewing-and-analyzing-your-traces)
  69 to view and analyze the trace you just recorded.