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   lttng-sessiond    ( 8 )

lTTng 2 демон сеанса трассировки (LTTng 2 tracing session daemon)

Имя (Name)

lttng-sessiond - LTTng 2 tracing session daemon

Синопсис (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]]

Описание (Description)

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.

Параметры (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).


           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.

Переменные окружения (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.

Файлы (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.

Статус выхода (Exit)

0 Success

1 Error

3 Fatal error

Ограничения (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.

Ошибки (баги) (Bugs)

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

Ресурсы (Resources)

• 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