lttng-clear(1) (v2.13)


lttng-clear — Clear an LTTng recording session


lttng [GENERAL OPTIONS] clear [SESSION | --all]


The lttng clear command clears one or more recording sessions, that is, it deletes the contents of their recording buffers and of all their local and streamed trace data.

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

The clear command clears:

Without any option

The current recording session.

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

With the SESSION argument

The recording session named SESSION.

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.

If a recording session is configured in snapshot mode (see the --snapshot option of the lttng-create(1) command), the clear command only clears the recording buffers.

For a given recording session, if at least one rotation occurred (see lttng-concepts(7)), the clear command only clears its recording buffers and its current trace chunk, not its archived trace chunks.

Note:The --disallow-clear option and the LTTNG_RELAYD_DISALLOW_CLEAR environment variable of lttng-relayd(8) can disable remote clearing operations. If LTTng sends recording data over the network for the selected recording session(s) to an LTTng relay daemon configured as such, the clear command fails.

See the “EXAMPLES” section below for usage examples.


Recording target

-a, --all

Clear 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), instead of the current recording session or the recording session named SESSION.

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 available command options and quit.





Command error


Undefined command


Fatal error


Command warning (something went wrong during the command)



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


Path to the LTTng home directory.

Defaults to $HOME.

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


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.


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


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.



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.


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

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


Unix user’s LTTng runtime and configuration directory.


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


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.


Example:Clear the current recording session.

lttng clear

Example:Clear a specific recording session.

lttng clear my-session

Example:Clear all recording sessions.

See the --all option.

lttng clear --all



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.