The Linux Trace Toolkit: next generation <http://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
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
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:
Apply command to the java.util.logging (JUL) domain.
Apply command to the Linux kernel domain.
Apply command to the Apache log4j 1.2
<https://logging.apache.org/log4j/1.2/> (Java) domain.
Apply command to the Python <https://www.python.org/> domain.
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
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
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.
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.
Do not automatically spawn a session daemon.
Suppress all messages, including warnings and errors.
Set the session daemon binary’s absolute path to PATH.
Three levels of verbosity are available, which are triggered by
appending additional v letters to the option (that is, -vv and
Program information-h, --help
List available commands.
List available general options.
Set to 1 to abort the process after the first error is
Overrides the $HOME environment variable. Useful when the user
running the commands has a non-writable home directory.
Absolute path to the man pager to use for viewing help
information about LTTng commands (using lttng-help(1) or lttngCOMMAND --help).
Path in which the session.xsd session configuration XML schema
may be found.
Full session daemon binary path.
The --sessiond-path option has precedence over this environment
Note that the lttng-create(1) command can spawn an LTTng session
daemon automatically if none is running. See lttng-sessiond(8) for
the environment variables influencing the execution of the session
User LTTng runtime configuration.
This is where the per-user current tracing session is stored
between executions of lttng(1). The current tracing session can
be set with lttng-set-session(1). See lttng-create(1) for more
information about tracing sessions.
Default output directory of LTTng traces. This can be overridden
with the --output option of the lttng-create(1) command.
User LTTng runtime and configuration directory.
Default location of saved user tracing sessions (see
lttng-save(1) and lttng-load(1)).
System-wide location of saved tracing sessions (see lttng-save(1)
Note$LTTNG_HOME defaults to $HOME when not explicitly set.
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
LTTng-tools is currently maintained by Jérémie Galarneau
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 firstname.lastname@example.org. This page was obtained
from the project's upstream Git repository
⟨git://git.lttng.org/lttng-tools.git⟩ on 2017-03-13. 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
LTTng 2.10.0-pre 03/13/2017 LTTNG(1)