lttng-start

NAME

lttng-start - Start an LTTng recording session

SYNOPSIS

lttng [GENERAL OPTIONS] start [SESSION]

DESCRIPTION

The lttng start command starts a recording session, that is, it activates the LTTng tracers for:

With the SESSION argument

The recording session named SESSION.

Without the SESSION argument

The current recording session (see lttng-concepts(7) to learn more about the current recording session).

See lttng-concepts(7) to learn more about recording sessions.

The selected recording session must be inactive (stopped). A recording session is inactive on creation (see lttng-create(1)).

A start-session trigger action can also start a recording session (see lttng-add-trigger(1)).

See the “EXAMPLES” section below for usage examples.

Stop an active recording session with the lttng-stop(1) command.

OPTIONS

See lttng(1) for GENERAL OPTIONS.

Program information

-h, --help

Show help.

This option attempts to launch /usr/bin/man to view this manual page. Override the manual pager path with the LTTNG_MAN_BIN_PATH environment variable.

--list-options

List available command options and quit.

EXIT STATUS

Success

Command error

Undefined command

Fatal error

Command warning (something went wrong during the command)

ENVIRONMENT

LTTNG_ABORT_ON_ERROR

Set to 1 to abort the process after the first error is encountered.

LTTNG_HOME

Path to the LTTng home directory.

Defaults to $HOME.

Useful when the Unix user running the commands has a non-writable home directory.

LTTNG_MAN_BIN_PATH

Absolute path to the manual pager to use to read the LTTng command-line help (with lttng-help(1) or with the --help option) instead of /usr/bin/man.

LTTNG_SESSION_CONFIG_XSD_PATH

Path to the directory containing the session.xsd recording session configuration XML schema.

LTTNG_SESSIOND_PATH

Absolute path to the LTTng session daemon binary (see lttng-sessiond(8)) to spawn from the lttng-create(1) command.

The --sessiond-path general option overrides this environment variable.

FILES

$LTTNG_HOME/.lttngrc

Unix user’s LTTng runtime configuration.

This is where LTTng stores the name of the Unix user’s current recording session between executions of lttng(1). lttng-create(1) and lttng-set-session(1) set the current recording session.

$LTTNG_HOME/lttng-traces

Default output directory of LTTng traces in local and snapshot modes.

Override this path with the --output option of the lttng-create(1) command.

$LTTNG_HOME/.lttng

Unix user’s LTTng runtime and configuration directory.

$LTTNG_HOME/.lttng/sessions

Default directory containing the Unix user’s saved recording session configurations (see lttng-save(1) and lttng-load(1)).

/etc/lttng/sessions

Directory containing the system-wide saved recording session configurations (see lttng-save(1) and lttng-load(1)).

Note

$LTTNG_HOME defaults to the value of the HOME environment variable.

EXAMPLES

Example 1. Start the current recording session.

$ lttng start

Example 2. Start a specific recording session.

$ lttng start my-session

RESOURCES

•LTTng project website <https://lttng.org>

•LTTng documentation <https://lttng.org/docs>

•LTTng bug tracker <https://bugs.lttng.org>

•Git repositories <https://git.lttng.org>

•GitHub organization <https://github.com/lttng>

•Continuous integration <https://ci.lttng.org/>

•Mailing list <https://lists.lttng.org/> for support and development: [email protected]

•IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net

COPYRIGHT

This program is part of the LTTng-tools project.

LTTng-tools is distributed under the GNU General Public License version 2 <http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html>. See the LICENSE <https://github.com/lttng/lttng-tools/blob/master/LICENSE> file for details.

THANKS

Special thanks to Michel Dagenais and the DORSAL laboratory <http://www.dorsal.polymtl.ca/> 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.