lttng-clear(1) (v2.12)


lttng-clear — Clear a tracing session


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


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

If no options are specified, the current tracing session is cleared (see lttng-create(1) for more information about the current tracing session).

If SESSION is specified, the existing tracing session named SESSION is cleared.

With the --all option, all the tracing sessions, as listed in the output of lttng list (see lttng-list(1)), are cleared.

If a tracing session is configured in snapshot mode (see the lttng-create(1) command’s --snapshot option), only the tracing buffers are cleared.

For a given tracing session, if at least one rotation occurred (see lttng-rotate(1)), only its tracing buffers and its current trace chunk are cleared; its archived trace chunks are not cleared.

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 tracing data over the network for SESSION (or for any tracing session with the --all option) to a relay daemon configured as such, lttng clear fails.


General options are described in lttng(1).


-a, --all

Clear all the tracing sessions instead of the current tracing session or the tracing session named SESSION.

Program information

-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 available command options.



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


Overrides the $HOME environment variable. Useful when the user running the commands has a non-writable home directory.


Absolute path to the man pager to use for viewing help information about LTTng commands (using lttng-help(1) or lttng COMMAND --help).


Path in which the session.xsd session configuration XML schema may be found.


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.



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.


Default output directory of LTTng traces. This can be overridden with the --output option of the lttng-create(1) command.


User LTTng runtime and configuration directory.


Default location of saved user tracing sessions (see lttng-save(1) and lttng-load(1)).


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.





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.



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.