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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | COMMANDS | EXIT STATUS | ENVIRONMENT | FILES | RESOURCES | COPYRIGHT | THANKS | SEE ALSO | COLOPHON |
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LTTNG(1) LTTng Manual LTTNG(1)
lttng - Control LTTng tracing
lttng [--group=GROUP] [--mi=xml] [--no-sessiond | --sessiond-path=PATH]
[--relayd-path=PATH] [--quiet | -verbose...]
COMMAND [COMMAND OPTIONS]
The Linux Trace Toolkit: next generation <https://lttng.org/> is
an open-source software package used for correlated tracing of the
Linux kernel, user applications, and user libraries.
LTTng consists of Linux kernel modules (for Linux kernel tracing)
and dynamically loaded libraries (for user application and library
tracing).
The lttng command-line tool, as well as any user application
linked with the LTTng control library (liblttng-ctl), sends
commands to a listening LTTng session daemon (lttng-sessiond(8)).
A session daemon:
• Manages recording sessions (see lttng-concepts(7) to learn
more about recording sessions).
• Controls the various components (like tracers and consumer
daemons) of LTTng.
• Sends asynchronous notifications to user applications.
By default, the lttng-create(1) command automatically spawns:
• A session daemon for your Unix user if none is currently
running.
Override the path of the session daemon binary to spawn with
the --sessiond-path option.
Avoid automatically spawning a session daemon with the --no-
sessiond option.
• A relay daemon (see lttng-relayd(8)) if all the following
statements are true:
• You specify the --live option.
• You don’t specify any of the --set-url, --ctrl-url, or
--data-url options.
• No relay daemon is currently listening for TCP connections
on 127.0.0.1:5344 (default LTTng live reader connection
address and port).
Override the path of the relay daemon binary to spawn with the
--relayd-path option.
Note
The LTTng project recommends that you start the session daemon
at boot time for stable and long-term tracing.
See lttng-concepts(7) to learn more about the foundational
concepts of LTTng.
The lttng tool offers a subcommand-based command-line interface.
The “COMMANDS” section below lists the available commands.
Session daemon connection
For most of its commands, the lttng tool needs to connect to a
listening LTTng session daemon (lttng-sessiond(8)) to control
LTTng tracing.
Each Unix user may have its own independent running session
daemon. However, the lttng tool must connect to the session daemon
of the root user (the root session daemon) to control Linux kernel
tracing.
How the lttng tool chooses which session daemon to connect to is
as follows:
If your Unix user is root
Connect to the root session daemon.
If your Unix user is not root
If your Unix user is part of the Unix tracing group
Try to connect to the root session daemon.
If the root session daemon isn’t running, connect to the
session daemon of your Unix user.
If your Unix user is not part of the tracing group
Connect to the session daemon of your Unix user.
The name of the Unix tracing group is one of:
With the --group=GROUP option of the root session daemon (‐
lttng-sessiond(8))
GROUP
In that case, you must use the --group=GROUP option, with the
same GROUP argument, of the lttng tool.
Without the --group option of the root session daemon
tracing
LTTng-instrumented user applications automatically register to
both the root and user session daemons. This makes it possible for
both session daemons to list the available instrumented
applications and their instrumentation points (see lttng-list(1)).
-g GROUP, --group=GROUP
Set the name of the Unix tracing group to GROUP instead of
tracing.
You must use this option to be able to connect to a root
session daemon (lttng-sessiond(8)) which was started with its
own --group=GROUP option.
-m xml, --mi=xml
Print the command result using a stable XML machine interface
(MI) output instead of the default, unstable human-readable
output.
With this mode, lttng prints the resulting XML document to the
standard output, while it prints any error/warning to the
standard error with an unstable, human-readable format.
If any error occurs during the execution of lttng, the command
exits with a status different than 0, and lttng does NOT
guarantee the syntax and data validity of its MI output.
An XML schema definition (XSD) file used for validation of the
MI output is available: see the src/common/mi_lttng.xsd file
in the LTTng-tools source tree.
-n, --no-sessiond
Do not automatically spawn a session daemon for your Unix user
when running the lttng-create(1) command.
You may NOT use this option with the --sessiond-path option.
-q, --quiet
Suppress all messages, including warnings and errors.
You may NOT use this option with the --verbose option.
--sessiond-path=PATH
Set the absolute path of the session daemon binary to spawn
from the lttng-create(1) command to PATH.
You may NOT use this option with the --no-sessiond option.
--relayd-path=PATH
Set the absolute path of the relay daemon binary to spawn from
the lttng-create(1) command to PATH.
-v, --verbose
Increase verbosity.
Specify this option up to three times to get more levels of
verbosity.
You may NOT use this option with the --quiet option.
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-options
List available command options and quit.
--list-commands
List available commands and quit.
-V, --version
Show version and quit.
The following commands also have their own --help option.
Recording session
┌───────────────────────────┬──────────────────────────┐
│ Command │ Description │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-create(1) │ Create a recording │
│ │ session. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-destroy(1) │ Destroy recording │
│ │ sessions. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-disable-rotation(1) │ Unset a recording │
│ │ session rotation │
│ │ schedule. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-enable-rotation(1) │ Set a recording session │
│ │ rotation schedule. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-load(1) │ Load recording session │
│ │ configurations. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-regenerate(1) │ Regenerate specific │
│ │ recording session data. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-rotate(1) │ Archive the current │
│ │ trace chunk of a │
│ │ recording session. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-save(1) │ Save recording session │
│ │ configurations. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-set-session(1) │ Set the current │
│ │ recording session. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-snapshot(1) │ Take a recording session │
│ │ snapshot. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-start(1) │ Start recording │
│ │ sessions. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-status(1) │ Show the status of the │
│ │ current recording │
│ │ session. │
├───────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-stop(1) │ Stop recording sessions. │
└───────────────────────────┴──────────────────────────┘
Channel
┌──────────────────────────┬──────────────────────────┐
│ Command │ Description │
├──────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-add-context(1) │ Add context fields to be │
│ │ recorded. │
├──────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-disable-channel(1) │ Disable channels. │
├──────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-enable-channel(1) │ Create or enable a │
│ │ channel. │
├──────────────────────────┼──────────────────────────┤
│ │ │
│ lttng-reclaim-memory(1) │ Reclaim channel memory. │
└──────────────────────────┴──────────────────────────┘
Recording event rule
┌────────────────────────┬─────────────────────────┐
│ Command │ Description │
├────────────────────────┼─────────────────────────┤
│ │ │
│ lttng-disable-event(1) │ Disable recording event │
│ │ rules. │
├────────────────────────┼─────────────────────────┤
│ │ │
│ lttng-enable-event(1) │ Create or enable │
│ │ recording event rules. │
└────────────────────────┴─────────────────────────┘
Information
┌───────────────┬─────────────────────────┐
│ Command │ Description │
├───────────────┼─────────────────────────┤
│ │ │
│ lttng-list(1) │ List recording sessions │
│ │ and instrumentation │
│ │ points. │
└───────────────┴─────────────────────────┘
Resource tracking
┌──────────────────┬──────────────────────────┐
│ Command │ Description │
├──────────────────┼──────────────────────────┤
│ │ │
│ lttng-track(1) │ Allow specific processes │
│ │ to record events. │
├──────────────────┼──────────────────────────┤
│ │ │
│ lttng-untrack(1) │ Disallow specific │
│ │ processes to record │
│ │ events. │
└──────────────────┴──────────────────────────┘
Trigger
┌─────────────────────────┬───────────────────┐
│ Command │ Description │
├─────────────────────────┼───────────────────┤
│ │ │
│ lttng-add-trigger(1) │ Add a trigger. │
├─────────────────────────┼───────────────────┤
│ │ │
│ lttng-list-triggers(1) │ List triggers. │
├─────────────────────────┼───────────────────┤
│ │ │
│ lttng-remove-trigger(1) │ Remove a trigger. │
└─────────────────────────┴───────────────────┘
Miscellaneous
┌──────────────────┬──────────────────────────┐
│ Command │ Description │
├──────────────────┼──────────────────────────┤
│ │ │
│ lttng-help(1) │ Show the help of a │
│ │ command. │
├──────────────────┼──────────────────────────┤
│ │ │
│ lttng-version(1) │ Show LTTng-tools version │
│ │ information. │
├──────────────────┼──────────────────────────┤
│ │ │
│ lttng-view(1) │ Launch a trace reader. │
└──────────────────┴──────────────────────────┘
0
Success
1
Command error
2
Undefined command
3
Fatal error
4
Command warning (something went wrong during the command)
LTTNG_ABORT_ON_ERROR
Set to 1 to abort the process after the first error is
encountered.
LTTNG_HOME
Path to the LTTng home directory.
Defaults to $HOME.
Useful when the Unix user running the commands has a
non-writable home directory.
LTTNG_LIST_LEGACY
Set to 1 to use the legacy output format (LTTng 2.14 and
earlier) for the lttng-list(1) command instead of the modern
output format.
Note that the legacy output doesn’t show anything related to
features introduced after LTTng 2.14.
LTTNG_MAN_BIN_PATH
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.
LTTNG_NO_UTF_8
Set to 1 to NOT emit multi-byte UTF-8 sequences, even if the
locale claims to support it.
LTTNG_SESSION_CONFIG_XSD_PATH
Path to the directory containing the session.xsd recording
session configuration XML schema.
LTTNG_SESSIOND_PATH
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.
LTTNG_TERM_COLOR
Controls when to emit terminal SGR codes in the output.
The NO_COLOR environment variable overrides this.
One of:
auto (default)
Only emit SGR codes when the standard output is connected
to a color-capable terminal.
always
Always emit SGR codes.
never
Never emit SGR codes.
NO_COLOR
If set and not empty, then it’s equivalent to setting
LTTNG_TERM_COLOR to never.
See NO_COLOR <https://no-color.org/> to learn more.
$LTTNG_HOME/.lttngrc
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.
$LTTNG_HOME/lttng-traces
Default output directory of LTTng traces in local and snapshot
modes.
Override this path with the --output option of the
lttng-create(1) command.
$LTTNG_HOME/.lttng
Unix user’s LTTng runtime and configuration directory.
$LTTNG_HOME/.lttng/sessions
Default directory containing the Unix user’s saved recording
session configurations (see lttng-save(1) and lttng-load(1)).
/usr/local/etc/lttng/sessions
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.
• LTTng project website <https://lttng.org>
• LTTng documentation <https://lttng.org/docs>
• LTTng bug tracker <https://bugs.lttng.org>
• Git repositories <https://git.lttng.org>
• GitHub organization <https://github.com/lttng>
• Continuous integration <https://ci.lttng.org/>
• Mailing list <https://lists.lttng.org/> for support and
development: lttng-dev@lists.lttng.org
• IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net
• Mastodon <https://mastodon.social/@lttng>
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-concepts(7) lttng-relayd(8), lttng-sessiond(8)
This page is part of the LTTng-Tools (LTTng tools) project.
Information about the project can be found at ⟨http://lttng.org/⟩.
It is not known how to report bugs for this man page; if you know,
please send a mail to man-pages@man7.org. This page was obtained
from the project's upstream Git repository
⟨https://github.com/lttng/lttng-tools.git⟩ on 2026-08-04. (At
that time, the date of the most recent commit that was found in
the repository was 2026-07-30.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
LTTng 2.15.1 4 December 2025 LTTNG(1)
Pages that refer to this page: lttng(1), lttng-add-context(1), lttng-add-trigger(1), lttng-clear(1), lttng-crash(1), lttng-create(1), lttng-destroy(1), lttng-disable-channel(1), lttng-disable-event(1), lttng-disable-rotation(1), lttng-enable-channel(1), lttng-enable-event(1), lttng-enable-rotation(1), lttng-help(1), lttng-list(1), lttng-list-triggers(1), lttng-load(1), lttng-metadata(1), lttng-reclaim-memory(1), lttng-regenerate(1), lttng-remove-trigger(1), lttng-rotate(1), lttng-save(1), lttng-set-session(1), lttng-snapshot(1), lttng-start(1), lttng-status(1), lttng-stop(1), lttng-track(1), lttng-untrack(1), lttng-version(1), lttng-view(1), lttng-health-check(3), lttng-ust(3), lttng-ust-cyg-profile(3), lttng-ust-dl(3), lttng_ust_tracef(3), lttng_ust_tracelog(3), babeltrace2-filter.lttng-utils.debug-info(7), lttng-concepts(7), lttng-event-rule(7), lttng-relayd(8), lttng-sessiond(8)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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