lttng [GENERAL OPTIONS] track (--kernel | --userspace)
[--session=SESSION] (--pid=PID[,PID]... | --all --pid)
The lttng track commands adds one or more entries to a resource tracker.
A resource tracker is a whitelist of resources. Tracked resources are allowed to emit events, provided those events are targeted by enabled event rules (see lttng-enable-event(1)).
Tracker entries can be removed from the whitelist with lttng-untrack(1).
As of this version, the only available tracker is the PID tracker. The process ID (PID) tracker follows one or more process IDs; only the processes with a tracked PID are allowed to emit events. By default, all possible PIDs on the system are tracked: any process may emit enabled events (equivalent of lttng track --pid --all for all domains).
With the PID tracker, it is possible, for example, to record all system calls called by a given process:
lttng enable-event --kernel --all --syscall lttng track --kernel --pid=2345 lttng start
If all the PIDs are tracked (i.e. lttng track --pid --all, which is the default state of all domains when creating a tracing session), then using the track command with one or more specific PIDs has the effect of first removing all the PIDs from the whitelist, then adding the specified PIDs.
Assume the maximum system PID is 7 for this example.
       
lttng track --userspace --pid=3,6,7
[ ] [ ] [ ]  [ ] [ ]  
lttng untrack --userspace --pid=7
[ ] [ ] [ ]  [ ] [ ]  [ ]
lttng track --userspace --pid=1,5
[ ]  [ ]  [ ]   [ ]
It should be noted that the PID tracker tracks the numeric process IDs. Should a process with a given ID exit and another process be given this ID, then the latter would also be allowed to emit events.
See the lttng-untrack(1) for more details about removing entries.
General options are described in lttng(1).
- Track resources in the Linux kernel domain.
- Track resources in the user space domain.
- Track resources in the tracing session named SESSION instead of the current tracing session.
- Used in conjunction with an empty --pid option: track all process IDs (add all entries to the whitelist).
Track process IDs
(add them to the current whitelist).
The PID argument must be omitted when also using the --all option.
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.
$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 <https://bugs.lttng.org/projects/lttng-tools>.
- • LTTng project website <http://lttng.org>
- • LTTng documentation <http://lttng.org/docs>
- • Git repositories <http://git.lttng.org>
- • GitHub organization <http://github.com/lttng>
- • Continuous integration <http://ci.lttng.org/>
- • IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net
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.
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.
LTTng-tools was originally written by Mathieu Desnoyers, Julien Desfossez, and David Goulet. More people have since contributed to it.
LTTng-tools is currently maintained by Jérémie Galarneau <mailto:[email protected]>.