lttng-start - Man Page

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

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)).

/usr/local/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

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)

Referenced By

lttng(1), lttng-add-context(1), lttng-add-trigger(1), lttng-concepts(7), lttng-create(1), lttng-disable-channel(1), lttng-disable-event(1), lttng-enable-channel(1), lttng-enable-event(1), lttng-snapshot(1), lttng-stop(1).

14 June 2021 LTTng 2.13.0 LTTng Manual