Ubuntu Manpage: lttng - LTTng 2 tracer control command-line tool

NAME

       lttng - LTTng 2 tracer control command-line tool

SYNOPSIS

       lttng [--group=GROUP] [--mi=TYPE] [--no-sessiond | --sessiond-path=PATH]
             [--quiet | -v | -vv | -vvv] COMMAND [COMMAND OPTIONS]

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).

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 package.

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:

-j, --jul
Apply command to the java.util.logging (JUL) domain.

-k, --kernel
Apply command to the Linux kernel domain.

-l, --log4j
Apply command to the Apache log4j 1.2 <https://logging.apache.org/log4j/1.2/> (Java) domain.

-p, --python
Apply command to the Python <https://www.python.org/> domain.

-u, --userspace
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 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.

Note

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.

OPTIONS

-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.

-n, --no-sessiond
Do not automatically spawn a session daemon.

-q, --quiet
Suppress all messages, including warnings and errors.

--sessiond-path=PATH
Set the session daemon binary’s absolute path to PATH.

-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).

Program information
-h, --help
Show help.

--list-commands
List available commands.

--list-options
List available general options.

-V, --version
Show version.

COMMANDS

       The following commands also have their own --help option.

   Tracing sessions
       lttng-create(1)
           Create a tracing session.

       lttng-destroy(1)
           Tear down tracing sessions.

       lttng-load(1)
           Load tracing session configurations.

       lttng-regenerate(1)
           Manage an LTTng tracing session’s data regeneration.

       lttng-save(1)
           Save tracing session configurations.

       lttng-set-session(1)
           Set current tracing session.

   Channels
       lttng-add-context(1)
           Add context fields to a channel.

       lttng-disable-channel(1)
           Disable tracing channels.

       lttng-enable-channel(1)
           Create or enable tracing channels.

   Event rules
       lttng-disable-event(1)
           Disable event rules.

       lttng-enable-event(1)
           Create or enable event rules.

   Status
       lttng-list(1)
           List tracing sessions, domains, channels, and events.

       lttng-status(1)
           Get the status of the current tracing session.

   Control
       lttng-snapshot(1)
           Snapshot buffers of current tracing session.

       lttng-start(1)
           Start tracing.

       lttng-stop(1)
           Stop tracing.

   Resource tracking
       lttng-track(1)
           Track specific system resources.

       lttng-untrack(1)
           Untrack specific system resources.

   Miscellaneous
       lttng-help(1)
           Display help information about a command.

       lttng-version(1)
           Show version information.

       lttng-view(1)
           Start trace viewer.

ENVIRONMENT VARIABLES

       LTTNG_ABORT_ON_ERROR
           Set to 1 to abort the process after the first error is encountered.

       LTTNG_HOME
           Overrides the $HOME environment variable. Useful when the user running the commands has a
           non-writable home directory.

       LTTNG_MAN_BIN_PATH
           Absolute path to the man pager to use for viewing help information about LTTng commands (using lttng-
           help(1) or lttng COMMAND --help).

       LTTNG_SESSION_CONFIG_XSD_PATH
           Path in which the session.xsd session configuration XML schema may be found.

       LTTNG_SESSIOND_PATH
           Full session daemon binary path.

           The --sessiond-path option has precedence over this environment variable.

       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 daemon.

FILES

       $LTTNG_HOME/.lttngrc
           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.

       $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
           User LTTng runtime and configuration directory.

       $LTTNG_HOME/.lttng/sessions
           Default location of saved user tracing sessions (see lttng-save(1) and lttng-load(1)).

       /usr/local/etc/lttng/sessions
           System-wide location of saved tracing sessions (see lttng-save(1) and lttng-load(1)).

           Note

           $LTTNG_HOME defaults to $HOME when not explicitly set.

EXIT STATUS

       0
           Success

       1
           Command error

       2
           Undefined command

       3
           Fatal error

       4
           Command warning (something went wrong during the command)

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>.