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LTTNG-START(1) LTTng Manual LTTNG-START(1)

NAME

lttng-start - Start one or more LTTng recording session

SYNOPSIS

lttng [GENERAL OPTIONS] start [--all | --glob=PATTERN | SESSION]

DESCRIPTION

The lttng start command starts one or more recording sessions, that is, it activates the LTTng tracers for:

With the SESSION argument

The recording session named SESSION.

With the --glob=PATTERN option

The recording sessions of which the globbing pattern PATTERN matches the name.

With the --all option

All the recording sessions of the connected session daemon for your Unix user, or for all users if your Unix user is root, as listed in the output of lttng list (see lttng-list(1)).

See the “Session daemon connection” section of lttng(1) to learn how a user application connects to a session daemon.

Otherwise

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(s) 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 one or more active recording sessions 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.

-a, --all

Start all the recording sessions of your Unix user, or of all users if your Unix user is root, as listed in the output of lttng-list(1).

-g PATTERN, --glob=PATTERN

Start the recording sessions of which the globbing pattern PATTERN matches the name.

In PATTERN, the * character means “match anything”. To match a literal * character, use \*.

EXIT STATUS

0

Success

1

Command error

2

Undefined command

3

Fatal error

4

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

Example 3. Start all the recording sessions.

See the --all option.

$ lttng start --all

Example 4. Start all the recording sessions of which the name ends with foo.

See the --glob option.

$ lttng start --glob='*foo'

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: lttng-dev@lists.lttng.org

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

•Mastodon <https://mastodon.social/@lttng>

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.

SEE ALSO

lttng(1), lttng-add-trigger(1), lttng-create(1), lttng-enable-event(1), lttng-stop(1), lttng-concepts(7)

1 April 2025 LTTng 2.14.0