lttng-snapshot(1) — Linux manual page


LTTNG-SNAPSHOT(1)             LTTng Manual             LTTNG-SNAPSHOT(1)

NAME         top

       lttng-snapshot - Take LTTng snapshots and configure snapshot

SYNOPSIS         top

       Add a snapshot output:

       lttng [GENERAL OPTIONS] snapshot add-output [--max-size=SIZE]
             [--name=NAME] [--session=SESSION]
             (--ctrl-url=URL --data-url=URL | URL)

       Remove a snapshot output:

       lttng [GENERAL OPTIONS] snapshot del-output [--session=SESSION]
             (ID | NAME)

       List current snapshot outputs:

       lttng [GENERAL OPTIONS] snapshot list-output [--session=SESSION]

       Take a snapshot:

       lttng [GENERAL OPTIONS] snapshot record [--max-size=SIZE]
             [--name=NAME] [--session=SESSION]
             (--ctrl-url=URL --data-url=URL | URL)

DESCRIPTION         top

       The lttng snapshot command manages the snapshot outputs and takes

       A snapshot is a dump of the current sub-buffers of all the
       channels of a given tracing session. When a snapshot is taken,
       the memory dump is sent to the registered snapshot outputs.

       The tracing session should be created in snapshot mode to make
       sure taking snapshots is allowed. This is done at tracing session
       creation time using the lttng-create(1) command.

       Note that, when a snapshot is taken, the sub-buffers are not
       cleared. This means that different recorded snapshots may contain
       the same events.

   Snapshot outputs
       Snapshot outputs are the destinations of snapshot files when a
       snapshot is taken using the record action.

       As of this version, only one snapshot output is allowed.

       A snapshot output can be added using the add-output action. The
       output destination URL is set using either the URL positional
       argument, or both the --ctrl-url and --data-url options. See
       lttng-create(1) to learn more about the URL format.

       A name can be assigned to an output when adding it using the
       --name option. This name is part of the names of the snapshot
       files written to this output.

       By default, the snapshot files can be as big as the sum of the
       sizes of all the sub-buffers or all the channels of the selected
       tracing session. The maximum total size of all the snapshot files
       can be configured using the --max-size option.

       Snapshot outputs can be listed using the list-output action.

       Snapshot outputs can be removed using the del-output action. The
       configured name can be used when removing an output, or an ID as
       listed by the list-output action.

   Taking a snapshot
       Taking a snapshot of the current tracing session is as easy as:

           $ lttng snapshot record

       This writes the snapshot files to the configured output. It is
       possible to use a custom, unregistered output at record time
       using the same options supported by the add-output action.

           Before taking a snapshot on a system with a high event
           throughput, it is recommended to first run lttng stop (see
           lttng-stop(1)). Otherwise, the snapshot could contain
           "holes", the result of the tracers overwriting unconsumed
           trace packets during the record operation. After the snapshot
           is recorded, the tracers can be started again with lttng
           start (see lttng-start(1)).

OPTIONS         top

       General options are described in lttng(1).

       -s SESSION, --session=SESSION
           Take a snapshot of the sub-buffers of the channels contained
           in the tracing session named SESSION instead of the current
           tracing session.

   Snapshot output
       -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).

       -m SIZE, --max-size=SIZE
           Limit the total size of all the snapshot files written when
           recording a snapshot to SIZE bytes. The k (kiB), M (MiB), and
           G (GiB) suffixes are supported.

       -n NAME, --name=NAME
           Assign the name NAME to the snapshot output.

   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


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
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       This page was obtained from the project's upstream Git repository
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       time, the date of the most recent commit that was found in the
       repository was 2019-11-14.)  If you discover any rendering
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       (which is not part of the original manual page), send a mail to

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

Pages that refer to this page: lttng(1)lttng-create(1)lttng-regenerate(1)lttng-rotate(1)