Ubuntu Manpage: lttng-sessiond - LTTng 2 tracing session daemon

NAME

       lttng-sessiond - LTTng 2 tracing session daemon

SYNOPSIS

       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]]

DESCRIPTION

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.

OPTIONS

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).

--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.

ENVIRONMENT VARIABLES

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.

FILES

       $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.

EXIT STATUS

       0
           Success

       1
           Error

       3
           Fatal error

LIMITATIONS

       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.

BUGS

       If you encounter any issue or usability problem, please report it on the LTTng bug tracker
       <https://bugs.lttng.org/projects/lttng-tools>.

RESOURCES

       •   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

COPYRIGHTS

       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.

THANKS

       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.

AUTHORS

       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>.