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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT VARIABLES | FILES | EXIT STATUS | LIMITATIONS | BUGS | RESOURCES | COPYRIGHTS | THANKS | AUTHORS | SEE ALSO | COLOPHON |
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LTTNG-SESSIOND(8) LTTng Manual LTTNG-SESSIOND(8)
lttng-sessiond - LTTng 2 tracing session daemon
lttng-sessiond [--background | --daemonize] [--sig-parent]
[--config=PATH] [--group=GROUP] [--load=PATH]
[--agent-tcp-port=PORT]
[--apps-sock=PATH] [--client-sock=PATH]
[--no-kernel | [--kmod-probes=PROBE[,PROBE]...]
[--extra-kmod-probes=PROBE[,PROBE]...]
[--kconsumerd-err-sock=PATH]
[--kconsumerd-cmd-sock=PATH]]
[--ustconsumerd32-err-sock=PATH]
[--ustconsumerd64-err-sock=PATH]
[--ustconsumerd32-cmd-sock=PATH]
[--ustconsumerd64-cmd-sock=PATH]
[--consumerd32-path=PATH] [--consumerd32-libdir=PATH]
[--consumerd64-path=PATH] [--consumerd64-libdir=PATH]
[--quiet | [-v | -vv | -vvv] [--verbose-consumer]]
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 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.
The LTTng session daemon manages trace data consumer daemons by
spawning them when necessary. You do not need to manage the
consumer daemons manually.
Note
It is highly recommended to start the session daemon at boot
time for stable and long-term tracing.
Automatic loading of tracing session configurations
When the session daemon starts, it automatically loads session
configuration files.
The following directories are searched, non-recursively, in this
order for configuration files to load on launch:
1. $LTTNG_HOME/.lttng/sessions/auto ($LTTNG_HOME defaults to
$HOME)
2. /usr/local/etc/lttng/sessions/auto
Note that both the directory containing the tracing session
configurations and the session daemon binary must share the same
UID for the configurations to be automatically loaded.
The --load option overrides the default directories and the UID
check. The session daemon simply checks if the path is accessible
and tries to load every tracing session configuration in it. When
this option is specified, the default directories are NOT
searched for configuration files. When the option is not
specified, both default directories are searched for
configuration files.
If the --load option’s argument is a directory, then all the
tracing session configurations found in all the files in this
directory are loaded. If the argument is a file, then all the
tracing session configurations found in this file are loaded.
Daemon configuration
-b, --background
Start as Unix daemon, but keep file descriptors (console)
open. Use the --daemonize option instead to close the file
descriptors.
-d, --daemonize
Start as Unix daemon, and close file descriptors (console).
Use the --background option instead to keep the file
descriptors open.
-f, --config=PATH
Load session daemon configuration from path PATH.
-g, --group=GROUP
Use GROUP as Unix tracing group (default: tracing).
-l, --load=PATH
Automatically load tracing session configurations from PATH,
either a directory or a file, instead of loading them from
the default search directories.
-S, --sig-parent
Send SIGUSR1 to parent process to notify readiness.
Note
This is used by lttng(1) to get notified when the session
daemon is ready to accept commands. When building a third
party tool on liblttng-ctl, this option can be very handy
to synchronize the control tool and the session daemon.
Linux kernel tracing
--extra-kmod-probes=PROBE[,PROBE]...
Load specific LTTng Linux kernel modules when kernel tracing
is enabled (--no-kernel option is NOT specified), in addition
to loading the default list of LTTng kernel modules.
Only the name of the probe needs to be specified, without the
lttng-probe- prefix and without the kernel module extension
suffix. For example, specify sched to load the lttng-probe-
sched.ko kernel module.
--kmod-probes=PROBE[,PROBE]...
Only load specific LTTng Linux kernel modules when kernel
tracing is enabled (--no-kernel option is NOT specified).
Only the name of the probe needs to be specified, without the
lttng-probe- prefix and without the kernel module extension
suffix. For example, specify sched to load the lttng-probe-
sched.ko kernel module.
--no-kernel
Disable Linux kernel tracing.
Paths and ports
--agent-tcp-port=PORT
Listen on TCP port PORT for agent application registrations
(default: a port within the range [5345, 5354]).
-a PATH, --apps-sock=PATH
Set application Unix socket path to PATH.
-c PATH, --client-sock=PATH
Set client Unix socket path to PATH.
--consumerd32-libdir=PATH
Set 32-bit consumer daemon library directory to PATH.
--consumerd32-path=PATH
Set 32-bit consumer daemon binary path to PATH.
--consumerd64-libdir=PATH
Set 64-bit consumer daemon library directory to PATH.
--consumerd64-path=PATH
Set 64-bit consumer daemon binary path to PATH.
--kconsumerd-cmd-sock=PATH
Set Linux kernel consumer daemon’s command Unix socket path
to PATH.
--kconsumerd-err-sock=PATH
Set Linux kernel consumer daemon’s error Unix socket path to
PATH.
--ustconsumerd32-cmd-sock=PATH
Set 32-bit consumer daemon’s command Unix socket path to
PATH.
--ustconsumerd64-cmd-sock=PATH
Set 64-bit consumer daemon’s command Unix socket path to
PATH.
--ustconsumerd32-err-sock=PATH
Set 32-bit consumer daemon’s error Unix socket path to PATH.
--ustconsumerd64-err-sock=PATH
Set 64-bit consumer daemon’s error Unix socket path to PATH.
Verbosity
-q, --quiet
Suppress all messages, including warnings and errors.
-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).
--verbose-consumer
Increase verbosity of consumer daemons spawned by this
session daemon.
Program information
-h, --help
Show help.
-V, --version
Show version.
Note that command-line options override their equivalent
environment variable.
LTTNG_ABORT_ON_ERROR
Set to 1 to abort the process after the first error is
encountered.
LTTNG_APP_SOCKET_TIMEOUT
Application socket’s timeout (seconds) when sending/receiving
commands. After this period of time, the application is
unregistered by the session daemon. A value of 0 or -1 means
an infinite timeout. Default value: 5.
LTTNG_CONSUMERD32_BIN
32-bit consumer daemon binary path.
The --consumerd32-path option overrides this variable.
LTTNG_CONSUMERD32_LIBDIR
32-bit consumer daemon library path.
The --consumerd32-libdir option overrides this variable.
LTTNG_CONSUMERD64_BIN
64-bit consumer daemon binary path.
The --consumerd64-path option overrides this variable.
LTTNG_CONSUMERD64_LIBDIR
64-bit consumer daemon library path.
The --consumerd64-libdir option overrides this variable.
LTTNG_DEBUG_NOCLONE
Set to 1 to disable the use of clone()/fork(). Setting this
variable is considered insecure, but it is required to allow
debuggers to work with the session daemon on some operating
systems.
LTTNG_EXTRA_KMOD_PROBES
Load specific LTTng Linux kernel modules when kernel tracing
is enabled (--no-kernel option is NOT specified), in addition
to loading the default list of LTTng kernel modules.
The --extra-kmod-probes option overrides this variable.
LTTNG_KMOD_PROBES
Only load specific LTTng Linux kernel modules when kernel
tracing is enabled (--no-kernel option is NOT specified).
The --kmod-probes option overrides this variable.
LTTNG_NETWORK_SOCKET_TIMEOUT
Socket connection, receive and send timeout (milliseconds). A
value of 0 or -1 uses the timeout of the operating system
(default).
LTTNG_SESSION_CONFIG_XSD_PATH
Tracing session configuration XML schema definition (XSD)
path.
$LTTNG_HOME/.lttng
User LTTng runtime and configuration directory.
$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/sessions/auto
Directory from which user tracing configuration files are
automatically loaded when the session daemon starts (see
lttng-save(1) and lttng-load(1) for saving and loading
tracing sessions).
/usr/local/etc/lttng/sessions/auto
Directory from which system-wide tracing configuration files
are automatically loaded when the session daemon starts (see
lttng-save(1) and lttng-load(1) for saving and loading
tracing sessions).
$LTTNG_HOME/.lttng/lttng.conf
Default location of the session daemon configuration file
(see the --config option).
/usr/local/etc/lttng/lttng.conf
System-wide location of the session daemon configuration file
(see the --config option).
Note
$LTTNG_HOME defaults to $HOME when not explicitly set.
0
Success
1
Error
3
Fatal error
For an unprivileged user running lttng-sessiond, the maximum
number of file descriptors per process is usually 1024. This
limits the number of traceable applications, since for each
instrumented application, there is two file descriptors per CPU
and one more socket for bidirectional communication.
For the root user, the limit is bumped to 65535. A future version
will deal with this limitation.
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(1), 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-SESSIOND(8)
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-relayd(8)
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HTML rendering created 2024-06-26 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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