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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 <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
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: 5345).
-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 <http://lttng.org>
· LTTng documentation <http://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 2017-07-05. 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 2.10.0-pre 05/03/2017 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-enable-channel(1), lttng-enable-event(1), lttng-help(1), lttng-list(1), lttng-load(1), lttng-metadata(1), lttng-regenerate(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)