contents/using-lttng/controlling-tracing/intro.md

   1 ---
   2 id: controlling-tracing
   3 ---
   4
   5 Once you're in possession of a software that is properly
   6 [instrumented](#doc-instrumenting) for LTTng tracing, be it thanks to
   7 the built-in LTTng probes for the Linux kernel, a custom user
   8 application or a custom Linux kernel, all that is left is actually
   9 tracing it. As a user, you control LTTng tracing using a single command
  10 line interface: the `lttng` tool. This tool uses `liblttng-ctl` behind
  11 the scene to connect to and communicate with session daemons. LTTng
  12 session daemons may either be started manually (`lttng-sessiond`) or
  13 automatically by the `lttng` command when needed. Trace data may
  14 be forwarded to the network and used elsewhere using an LTTng relay
  15 daemon (`lttng-relayd`).
  16
  17 The manpages of `lttng`, `lttng-sessiond` and `lttng-relayd` are pretty
  18 complete, thus this section is not an online copy of the latter (we
  19 leave this contents for the
  20 [Online LTTng manpages](#doc-online-lttng-manpages) section).
  21 This section is rather a tour of LTTng
  22 features through practical examples and tips.
  23
  24 If not already done, make sure you understand the core concepts
  25 and how LTTng components connect together by reading the
  26 [Understanding LTTng](#doc-understanding-lttng) chapter; this section
  27 assumes you are familiar with them.