lttng-create(1) — Linux manual page


LTTNG-CREATE(1)               LTTng Manual               LTTNG-CREATE(1)

NAME         top

       lttng-create - Create an LTTng tracing session

SYNOPSIS         top

       Local mode:

       lttng [GENERAL OPTIONS] create [SESSION] [--shm-path=PATH]
             [--no-output | --output=PATH | --set-url=file://PATH]

       Network streaming mode:

       lttng [GENERAL OPTIONS] create [SESSION] [--shm-path=PATH]
             (--set-url=URL | --ctrl-url=URL --data-url=URL)

       Snapshot mode:

       lttng [GENERAL OPTIONS] create [SESSION] --snapshot
             [--shm-path=PATH] [--set-url=URL | --ctrl-url=URL --data-url=URL]

       Live mode:

       lttng [GENERAL OPTIONS] create [SESSION] --live[=DELAYUS]
             [--shm-path=PATH] [--set-url=URL | --ctrl-url=URL --data-url=URL]

DESCRIPTION         top

       The lttng create command creates a new tracing session.

       A tracing session is a named container of channels, which in turn
       contain event rules. It is domain-agnostic, in that channels and
       event rules can be enabled for the user space tracer and/or the
       Linux kernel tracer.

       On execution, an .lttngrc file is created, if it does not exist,
       in the user’s home directory. This file contains the name of the
       current tracing session. When creating a new tracing session with
       lttng create, the current tracing session is set to this new
       tracing session. The lttng-set-session(1) command can be used to
       set the current tracing session without manually editing the
       .lttngrc file.

       If SESSION is omitted, a session name is automatically created
       having this form: auto-YYYYmmdd-HHMMSS. SESSION must not contain
       the character /.

       The --shm-path option can be used to specify the path to the
       shared memory holding the ring buffers. Specifying a location on
       an NVRAM file system makes it possible to retrieve the latest
       recorded trace data when the system reboots after a crash. To
       view the events of ring buffer files after a system crash, use
       the lttng-crash(1) utility.

       Tracing sessions are destroyed using the lttng-destroy(1)

   Creation modes
       There are four tracing session modes:

       Local mode
           Traces the local system and writes the trace to the local
           file system. The --output option specifies the trace path.
           Using --set-url=file://PATH is the equivalent of using
           --output=PATH. The file system output can be disabled using
           the --no-output option.

           If none of the options mentioned above are used, then the
           trace is written locally in the $LTTNG_HOME/lttng-traces
           directory ($LTTNG_HOME defaults to $HOME).

       Network streaming mode
           Traces the local system and sends the trace over the network
           to a listening relay daemon (see lttng-relayd(8)). The --set-
           url, or --ctrl-url and --data-url options set the trace
           output destination (see the URL format section below).

       Snapshot mode
           Traces the local system without writing the trace to the
           local file system (implicit --no-output option). Channels are
           automatically configured to be snapshot-ready on creation
           (see lttng-enable-channel(1)). The lttng-snapshot(1) command
           is used to take snapshots of the current ring buffers. The
           --set-url, or --ctrl-url and --data-url options set the
           default snapshot output destination.

       Live mode
           Traces the local system, sending trace data to an LTTng relay
           daemon over the network (see lttng-relayd(8)). The --set-url,
           or --ctrl-url and --data-url options set the trace output
           destination. The live output URLs cannot use the file://
           protocol (see the URL format section below).

   URL format
       The --set-url, --ctrl-url, and --data-url options' arguments are

       The format of those URLs is one of:


       The file:// protocol targets the local file system and can only
       be used as the --set-url option’s argument when the session is
       created in local or snapshot mode.

           Absolute path to trace files on the local file system.

       The other version is available when the session is created in
       network streaming, snapshot, or live mode.

           Network protocol, amongst:

               TCP over IPv4; the default values of CTRLPORT and
               DATAPORT are respectively 5342 and 5343.

               TCP over IPv6: same default ports as the net protocol.

               Same as the net protocol; can only be used with the
               --ctrl-url and --data-url options together.

               Same as the net6 protocol; can only be used with the
               --ctrl-url and --data-url options together.

       (HOST | IPADDR)
           Hostname or IP address (IPv6 address must be enclosed in
           brackets ([ and ]); see RFC 2732

           Control port.

           Data port.

           Path of trace files on the remote file system. This path is
           relative to the base output directory set on the relay daemon
           side; see lttng-relayd(8).

OPTIONS         top

       General options are described in lttng(1).

   Mode selection
           Create the session in live mode.

           The optional DELAYUS parameter, given in microseconds, is the
           maximum time the user can wait for the data to be flushed.
           This mode can be set with a network URL (options --set-url,
           or --ctrl-url and --data-url) and must have a relay daemon
           listening (see lttng-relayd(8)).

           By default, DELAYUS is 1000000 and the network URL is set to

           Create the session in snapshot mode. This is the equivalent
           of using the --no-output option and creating all the channels
           of this new tracing session in overwrite mode with an mmap
           output type.

           In local mode, do not output any trace data.

       -o PATH, --output=PATH
           In local mode, set trace output path to PATH.

           Create shared memory holding buffers at PATH.

       See the URL format section above for more information about the
       syntax of the following options' URL argument.

       -C URL, --ctrl-url=URL
           Set control path URL to URL (must use --data-url option

       -D URL, --data-url=URL
           Set data path URL to URL (must use --ctrl-url option also).

       -U URL, --set-url=URL
           Set URL destination of the trace data to URL. It is
           persistent for the session lifetime. This option sets both
           data (--data-url option) and control (--ctrl-url option) URLs
           at the same time.

           In local mode, URL must start with file:// followed by the
           destination path on the local file system.

   Program information
       -h, --help
           Show command help.

           This option, like lttng-help(1), attempts to launch
           /usr/bin/man to view the command’s man page. The path to the
           man pager can be overridden by the LTTNG_MAN_BIN_PATH
           environment variable.

           List available command options.


           Set to 1 to abort the process after the first error is

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

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

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

           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         top

           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.

           Default output directory of LTTng traces. This can be
           overridden with the --output option of the lttng-create(1)

           User LTTng runtime and configuration directory.

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

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


           $LTTNG_HOME defaults to $HOME when not explicitly set.

EXIT STATUS         top


           Command error

           Undefined command

           Fatal error

           Command warning (something went wrong during the command)

BUGS         top

       If you encounter any issue or usability problem, please report it
       on the LTTng bug tracker <

RESOURCES         top

       •   LTTng project website <>

       •   LTTng documentation <>

       •   Git repositories <>

       •   GitHub organization <>

       •   Continuous integration <>

       •   Mailing list <> for support and

       •   IRC channel <irc://>: #lttng on

COPYRIGHTS         top

       This program is part of the LTTng-tools project.

       LTTng-tools is distributed under the GNU General Public License
       version 2 <
       licenses/gpl-2.0.en.html>. See the LICENSE
       <> file
       for details.

THANKS         top

       Special thanks to Michel Dagenais and the DORSAL laboratory
       <> 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         top

       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

SEE ALSO         top

       lttng-destroy(1), lttng-set-session(1), lttng(1)

COLOPHON         top

       This page is part of the LTTng-Tools (    LTTng tools) project.
       Information about the project can be found at 
       ⟨⟩.  It is not known how to report bugs for this
       man page; if you know, please send a mail to
       This page was obtained from the project's upstream Git repository
       ⟨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

LTTng 2.12.0-pre               10/29/2018                LTTNG-CREATE(1)

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