lttng-track - Man Page

Add one or more values to an LTTng process attribute tracker

Synopsis

Add specific process attribute values to a Linux kernel domain tracker:

lttng [GENERAL OPTIONS] track --kernel
      (--pid=PID[,PID]... | --vpid=VPID[,VPID]... |
      --uid=UID[,UID]... | --vuid=VUID[,VUID]... |
      --gid=GID[,GID]... | --vgid=VGID[,VGID]... )...

Add all possible process attribute values to a Linux kernel domain tracker:

lttng [GENERAL OPTIONS] track --kernel
      --all (--pid | --vpid | --uid |
      --vuid | --gid | --vgid )...

Add specific process attribute values to a user space domain tracker:

lttng [GENERAL OPTIONS] track --userspace
      (--vpid=VPID[,VPID]... | --vuid=VUID[,VUID]... | --vgid=VGID[,VGID]...)...

Add all possible process attribute values to a user space domain tracker:

lttng [GENERAL OPTIONS] track --userspace
      --all (--vpid | --vgid | --vuid)...

Description

The lttng track commands adds one or more values to a process attribute tracker.

A process attribute tracker is an inclusion set of process attributes. Tracked processes are allowed to emit events, provided those events are targeted by enabled event rules (see lttng-enable-event(1)).

Tracker values can be removed from an inclusion set with lttng-untrack(1).

The available process attribute trackers are:

A tracker follows one or more process attribute values; only the processes with a tracked value are allowed to emit events. By default, all possible values on the system are tracked: any process may emit enabled events, the equivalent of:

$ lttng track --kernel --pid --vpid --uid --vuid --gid --vgid --all
$ lttng track --userspace --vpid --vuid --vgid --all

With the PID tracker, for example, you can record all system calls of a given process:

$ lttng enable-event --kernel --all --syscall
$ lttng track --kernel --pid=2345
$ lttng start

If all the PIDs are tracked (with the --pid and --all options), 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 inclusion set, then adding the specified PIDs.

Example

Assume the maximum system PID is 7 for this example.

Initial inclusion set:

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

Command:

$ lttng track --kernel --pid=3,6,7

inclusion set:

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

Command:

$ lttng untrack --kernel --pid=7

inclusion set:

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

Command:

$ lttng track --kernel --pid=1,5

inclusion set:

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

See the lttng-untrack(1) for more details about removing values from the inclusion set.

Options

General options are described in lttng(1).

Domain

One of:

-k, --kernel

Track process attributes in the Linux kernel domain.

-u, --userspace

Track process attributes in the user space domain.

Target

-s SESSION, --session=SESSION

Track process attributes in the tracing session named SESSION instead of the current tracing session.

Tracking

-a, --all

Used in conjunction with a single, empty --pid, --vpid, --uid, --vuid, --gid, or --vgid option: track all possible process attribute values (add all values to the inclusion set).

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

Track process ID values PID (add them to the process ID inclusion set).

PID is the process ID attribute of a process as seen from the root PID namespace (see pid_namespaces(7)). It can only be used with the --kernel domain option.

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

--vpid[=VPID[,VPID]...]

Track virtual process ID values VPID (add them to the virtual process ID inclusion set).

VPID is the virtual process ID attribute of a process as seen from the PID namespace of the process (see pid_namespaces(7)).

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

--uid[=USER[,USER]...]

Track user ID process attribute values USER (add them to the user ID inclusion set).

USER is the real user ID (see getuid(3)) of a process as seen from the root user namespace (see user_namespaces(7)). It can only be used with the --kernel domain option.

USER can also be a user name. The user name resolution is performed by the session daemon (see lttng-sessiond(8)) on addition to the user ID inclusion set.

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

--vuid[=USER[,USER]...]

Track virtual user ID process attribute values USER (add them to the virtual user ID inclusion set).

USER is the real user ID (see getuid(3)) of a process as seen from the user namespace of the process (see user_namespaces(7)).

USER can also be a user name. The user name resolution is performed by the session daemon (see lttng-sessiond(8)) on addition to the virtual user ID inclusion set.

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

--gid[=GROUP[,GROUP]...]

Track group ID process attribute values GROUP (add them to the group ID inclusion set).

GROUP is the real group ID (see getgid(3)) of a process as seen from the root user namespace (see user_namespaces(7)). It can only be used with the --kernel domain option.

GROUP can also be a group name. The group name resolution is performed by the session daemon (see lttng-sessiond(8)) on addition to the group ID inclusion set.

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

--vgid[=GROUP[,GROUP]...]

Track virtual group ID process attribute values GROUP(add them to the virtual group ID inclusion set).

GROUP is the real group ID (see getgid(3)) of a process as seen from the user namespace of the process (see user_namespaces(7)).

GROUP can also be a group name. The group name resolution is performed by the session daemon (see lttng-sessiond(8)) on addition to the virtual group ID inclusion set.

The GROUP 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.

Environment Variables

LTTNG_ABORT_ON_ERROR

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

LTTNG_HOME

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

LTTNG_MAN_BIN_PATH

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

LTTNG_SESSION_CONFIG_XSD_PATH

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

LTTNG_SESSIOND_PATH

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.

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.

Exit Status

0

Success

1

Command error

2

Undefined command

3

Fatal error

4

Command warning (something went wrong during the command)

Bugs

If you encounter any issue or usability problem, please report it on the LTTng bug tracker <https://bugs.lttng.org/projects/lttng-tools>.

Resources

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.

See Also

lttng-untrack(1), lttng(1)

Referenced By

lttng(1), lttng-enable-event(1), lttng-untrack(1).

4 March 2020 LTTng 2.12.2 LTTng Manual