lttng-start — Start LTTng tracers
lttng [GENERAL OPTIONS] start [SESSION]The lttng start command starts the various LTTng tracers for a
given inactive tracing session.
Starting the LTTng tracers has the effect that all enabled event rules within enabled channels can make their target event sources emit trace events. Whether they are recorded to the local file system, sent over the network, or not recorded at all depends on the specific configuration of the tracing session in which tracing is started. See lttng-create(1) for different session modes.
A tracing session with running tracers is said to be active. Active tracing sessions can return to the inactive state using the lttng-stop(1) command.
If SESSION is omitted, the LTTng tracers are started for the current
tracing session (see lttng-create(1) for more information
about the current tracing session). Otherwise, they are started for the
existing tracing session named SESSION. lttng list
outputs all the existing tracing sessions (see lttng-list(1)).
General options are described in lttng(1).
-h, --help
Show command help.
This option, like lttng-help(1), attempts to launch
/usr/bin/man to view the command’s man page. The path to the man pager
can be overridden by the LTTNG_MAN_BIN_PATH environment variable.
--list-options
List available command options.
LTTNG_ABORT_ON_ERROR
Set to 1 to abort the process after the first error is encountered.
LTTNG_HOME
Overrides the $HOME environment variable. Useful when the user
running the commands has a non-writable home directory.
LTTNG_MAN_BIN_PATH
Absolute path to the man pager to use for viewing help information
about LTTng commands (using lttng-help(1) or
lttng COMMAND --help).
LTTNG_SESSION_CONFIG_XSD_PATH
Path in which the session.xsd session configuration XML
schema may be found.
LTTNG_SESSIOND_PATH
Full session daemon binary path.
The --sessiond-path option has precedence over this
environment variable.
Note that the lttng-create(1) command can spawn an LTTng session daemon automatically if none is running. See lttng-sessiond(8) for the environment variables influencing the execution of the session daemon.
$LTTNG_HOME/.lttngrc
User LTTng runtime configuration.
This is where the per-user current tracing session is stored between executions of lttng(1). The current tracing session can be set with lttng-set-session(1). See lttng-create(1) for more information about tracing sessions.
$LTTNG_HOME/lttng-traces
Default output directory of LTTng traces. This can be overridden
with the --output option of the lttng-create(1)
command.
$LTTNG_HOME/.lttng
User LTTng runtime and configuration directory.
$LTTNG_HOME/.lttng/sessions
Default location of saved user tracing sessions (see lttng-save(1) and lttng-load(1)).
/etc/lttng/sessions
System-wide location of saved tracing sessions (see lttng-save(1) and lttng-load(1)).
Note:$LTTNG_HOME defaults to $HOME when not explicitly set.
Success
Command error
Undefined command
Fatal error
Command warning (something went wrong during the command)
If you encounter any issue or usability problem, please report it on the LTTng bug tracker.
Mailing list for support and
development: lttng-dev@lists.lttng.org
IRC channel: #lttng on irc.oftc.net
This program is part of the LTTng-tools project.
LTTng-tools is distributed under the
GNU General
Public License version 2. See the
LICENSE file
for details.
Special thanks to Michel Dagenais and the DORSAL laboratory at École Polytechnique de Montréal for the LTTng journey.
Also thanks to the Ericsson teams working on tracing which helped us greatly with detailed bug reports and unusual test cases.