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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | COMMANDS | ENVIRONMENT VARIABLES | FILES | EXIT STATUS | BUGS | RESOURCES | COPYRIGHTS | THANKS | AUTHORS | SEE ALSO | COLOPHON |
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LTTNG(1) LTTng Manual LTTNG(1)
lttng - LTTng 2 tracer control command-line tool
lttng [--group=GROUP] [--mi=TYPE] [--no-sessiond | --sessiond-path=PATH]
[--quiet | -v | -vv | -vvv] 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).
An LTTng session daemon, lttng-sessiond(8), receives commands from
the command-line interface lttng to control the LTTng tracers. All
interactions with the LTTng tracers happen through the lttng tool
or through the liblttng-ctl library shipped with the LTTng-tools
package.
A tracing domain is a tracer category. There are five available
domains. For some commands, the domain needs to be specified with
a command-line option. The domain options are:
-j, --jul
Apply command to the java.util.logging (JUL) domain.
-k, --kernel
Apply command to the Linux kernel domain.
-l, --log4j
Apply command to the Apache log4j 1.2
<https://logging.apache.org/log4j/1.2/> (Java) domain.
-p, --python
Apply command to the Python <https://www.python.org/> domain.
-u, --userspace
Apply command to the user space domain (application using
liblttng-ust directly; see lttng-ust(3)).
The LTTng session daemon is a tracing registry which allows the
user to interact with multiple tracers (kernel and user space)
within the same container, a tracing session. Traces can be
gathered from the Linux kernel and/or from instrumented
applications (see lttng-ust(3)). You can aggregate and read the
events of LTTng traces using babeltrace(1).
To trace the Linux kernel, the session daemon needs to be running
as root. LTTng uses a tracing group to allow specific users to
interact with the root session daemon. The default tracing group
name is tracing. You can use the --group option to set the tracing
group name to use.
Session daemons can coexist. You can have a session daemon running
as user Alice that can be used to trace her applications alongside
a root session daemon or a session daemon running as user Bob.
Note
It is highly recommended to start the session daemon at boot
time for stable and long-term tracing.
User applications instrumented with LTTng automatically register
to the root session daemon and to user session daemons. This
allows any session daemon to list the available traceable
applications and event sources (see lttng-list(1)).
By default, the lttng-create(1) command automatically spawns a
user session daemon if none is currently running. The --no-
sessiond general option can be set to avoid this.
-g GROUP, --group=GROUP
Use GROUP as Unix tracing group (default: tracing).
-m TYPE, --mi=TYPE
Print the command’s result using the machine interface type
TYPE instead of a human-readable output.
Supported types: xml.
The machine interface (MI) mode converts the traditional
pretty-printing to a machine output syntax. The MI mode
provides a change-resistant way to access information
generated by the lttng command-line program.
When using the MI mode, the data is printed to the standard
output. Errors and warnings are printed on the standard error
with the pretty-print default format.
If any error occurs during the execution of a command, the
return value of the command will be different than 0. In this
case, lttng does NOT guarantee the syntax and data validity of
the generated MI output.
For the xml MI type, an XML schema definition (XSD) file used
for validation 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.
-q, --quiet
Suppress all messages, including warnings and errors.
--sessiond-path=PATH
Set the session daemon binary’s absolute path to PATH.
-v, --verbose
Increase verbosity.
Three levels of verbosity are available, which are triggered
by appending additional v letters to the option (that is, -vv
and -vvv).
Program information
-h, --help
Show help.
--list-commands
List available commands.
--list-options
List available general options.
-V, --version
Show version.
The following commands also have their own --help option.
Tracing sessions
lttng-create(1)
Create a tracing session.
lttng-destroy(1)
Tear down tracing sessions.
lttng-load(1)
Load tracing session configurations.
lttng-regenerate(1)
Manage an LTTng tracing session’s data regeneration.
lttng-save(1)
Save tracing session configurations.
lttng-set-session(1)
Set current tracing session.
Channels
lttng-add-context(1)
Add context fields to a channel.
lttng-disable-channel(1)
Disable tracing channels.
lttng-enable-channel(1)
Create or enable tracing channels.
Event rules
lttng-disable-event(1)
Disable event rules.
lttng-enable-event(1)
Create or enable event rules.
Status
lttng-list(1)
List tracing sessions, domains, channels, and events.
lttng-status(1)
Get the status of the current tracing session.
Control
lttng-snapshot(1)
Snapshot buffers of current tracing session.
lttng-start(1)
Start tracing.
lttng-stop(1)
Stop tracing.
Tracing session rotation
lttng-disable-rotation(1)
Unset a rotation schedule.
lttng-enable-rotation(1)
Set a rotation schedule.
lttng-rotate(1)
Archive a tracing session’s current trace chunk.
Resource tracking
lttng-track(1)
Track specific system resources.
lttng-untrack(1)
Untrack specific system resources.
Miscellaneous
lttng-help(1)
Display help information about a command.
lttng-version(1)
Show version information.
lttng-view(1)
Start trace viewer.
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.
$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.
0
Success
1
Command error
2
Undefined command
3
Fatal error
4
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 <https://lttng.org>
• LTTng documentation <https://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: lttng-dev@lists.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:jeremie.galarneau@efficios.com>.
lttng-sessiond(8), lttng-relayd(8), lttng-crash(1), lttng-ust(3),
babeltrace(1)
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
⟨git://git.lttng.org/lttng-tools.git⟩ on 2019-11-19. (At that
time, the date of the most recent commit that was found in the
repository was 2019-11-14.) 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 2.12.0-pre 10/29/2018 LTTNG(1)
Pages that refer to this page: lttng(1), lttng-add-context(1), lttng-calibrate(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-load(1), lttng-metadata(1), lttng-regenerate(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-relayd(8), lttng-sessiond(8)
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HTML rendering created 2025-09-06 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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