SYNOPSIS

lttng [GENERAL OPTIONS] track (--kernel | --userspace)
[--session=SESSION] (--pid=PID[,PID]... | --all --pid)

DESCRIPTION

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.

Example

Assume the maximum system PID is 7 for this example.

Initial whitelist:

[0] [1] [2] [3] [4] [5] [6] [7]

Command:

lttng track --userspace --pid=3,6,7

Whitelist:

[ ] [ ] [ ] [3] [ ] [ ] [6] [7]

Command:

lttng untrack --userspace --pid=7

Whitelist:

[ ] [ ] [ ] [3] [ ] [ ] [6] [ ]

Command:

lttng track --userspace --pid=1,5

Whitelist:

[ ] [1] [ ] [3] [ ] [5] [6] [ ]

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.

OPTIONS

General options are described in lttng(1).

Domain

One of:

-k, --kernel

Track resources in the Linux kernel domain.

-u, --userspace

Track resources in the user space domain.

Target

-s, --session=SESSION

Track resources in the tracing session named SESSION instead of the current tracing session.

Tracking

-a, --all

Used in conjunction with an empty --pid option: track all process IDs (add all entries to the whitelist).

-p, --pid[=PID[,PID]...]

Track process IDs PID (add them to the current whitelist).

The PID argument must be omitted when also using the --all option.

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-options

List available command options.

FILES

$LTTNG_HOME/.lttngrc

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.

$LTTNG_HOME/lttng-traces

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

$LTTNG_HOME/.lttng

User LTTng runtime and configuration directory.

$LTTNG_HOME/.lttng/sessions

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

/usr/local/etc/lttng/sessions

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.

RESOURCES

• 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/>

• Mailing list <http://lists.lttng.org> for support and development: [email protected]

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

COPYRIGHTS

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.

AUTHORS

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]>.