+* A session daemon for your Unix user if none is currently running.
++
+Override the path of the session daemon binary to spawn with the
+option:--sessiond-path option.
++
+Avoid automatically spawning a session daemon with the
+option:--no-sessiond option.
+
+* A relay daemon (see man:lttng-relayd(8)) if all the following
+ statements are true:
++
+--
+* You specify the nloption:--live option.
+
+* You don't specify any of the nloption:--set-url, nloption:--ctrl-url,
+ or nloption:--data-url options.
+
+* No relay daemon is currently listening for TCP connections on
+ +127.0.0.1:{default_network_viewer_port}+ (default LTTng live reader
+ connection address and port).
+--
++
+Override the path of the relay daemon binary to spawn with the
+option:--relayd-path option.
+
+NOTE: The LTTng project recommends that you start the session daemon at
+boot time for stable and long-term tracing.
+
+See man:lttng-concepts(7) to learn more about the foundational concepts
+of LTTng.
+
+The `lttng` tool offers a subcommand-based command-line interface. The
+<<commands,COMMANDS>> section below lists the available commands.
+
+
+Session daemon connection
+~~~~~~~~~~~~~~~~~~~~~~~~~
+For most of its commands, the `lttng` tool needs to connect to a
+listening LTTng session daemon (man:lttng-sessiond(8)) to control LTTng
+tracing.