Ubuntu Manpage: lttng-regenerate - Regenerate specific data of an LTTng recording session

NAME

       lttng-regenerate - Regenerate specific data of an LTTng recording session

SYNOPSIS

       Regenerate the metadata of a recording session:

       lttng [GENERAL OPTIONS] regenerate metadata [--session=SESSION]

       Regenerate the state dump event records of a recording session:

       lttng [GENERAL OPTIONS] regenerate statedump [--session=SESSION]

DESCRIPTION

The lttng regenerate command regenerates specific data of:

With the --session=SESSION option
The recording session named SESSION.

Without the --session option
The current recording session (see lttng-concepts(7) to learn more about the current
recording session).

See lttng-concepts(7) to learn more about recording sessions.

As of this version, the metadata and statedump targets are available.

See the “EXAMPLES” section below for usage examples.

Regenerate the metadata of a recording session
Use the metadata target to resample the offset between the monotonic clock and the wall
time of the system, and then regenerate the metadata stream files.

More specifically, you may want to resample the wall time following a major NTP
<https://en.wikipedia.org/wiki/Network_Time_Protocol> correction. As such, LTTng can trace
a system booting with an incorrect wall time before its wall time is NTP-corrected.
Regenerating the metadata of the selected recording session ensures that trace readers can
accurately determine the event record timestamps relative to the Unix epoch.

Note that if you plan to rotate (see lttng-concepts(7) to learn more) the selected
recording session, this target only regenerates the metadata stream files of the current
and next trace chunks.

Important
You can only use the metadata target when the selected recording session:

• Is not in live mode (--live option of lttng-create(1)).

• If it has user space channels, they’re configured to use a per-user buffering
scheme (--buffers-uid option of lttng-enable-channel(1)).

See lttng-concepts(7) to learn more about channels.

Regenerate the state dump event records of a recording session
Use the statedump target to collect up-to-date state dump information and create
corresponding event records.

This is particularly useful if the selected recording session is in snapshot mode
(--snapshot option of the lttng-create(1) command) or if LTTng rotates trace files for one
of its channels (see lttng-concepts(7)): in both cases, the state dump information may be
lost.

OPTIONS

       See lttng(1) for GENERAL OPTIONS.

       -s SESSION, --session=SESSION
           Regenerate specific data of the recording session named SESSION instead of the current
           recording session.

   Program information
       -h, --help
           Show help.

           This option attempts to launch /usr/bin/man to view this manual page. Override the
           manual pager path with the LTTNG_MAN_BIN_PATH environment variable.

       --list-options
           List available command options and quit.

EXIT STATUS

       0
           Success

       1
           Command error

       2
           Undefined command

       3
           Fatal error

       4
           Command warning (something went wrong during the command)

ENVIRONMENT

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

       LTTNG_HOME
           Path to the LTTng home directory.

           Defaults to $HOME.

           Useful when the Unix user running the commands has a non-writable home directory.

       LTTNG_MAN_BIN_PATH
           Absolute path to the manual pager to use to read the LTTng command-line help (with
           lttng-help(1) or with the --help option) instead of /usr/bin/man.

       LTTNG_SESSION_CONFIG_XSD_PATH
           Path to the directory containing the session.xsd recording session configuration XML
           schema.

       LTTNG_SESSIOND_PATH
           Absolute path to the LTTng session daemon binary (see lttng-sessiond(8)) to spawn from
           the lttng-create(1) command.

           The --sessiond-path general option overrides this environment variable.

FILES

       $LTTNG_HOME/.lttngrc
           Unix user’s LTTng runtime configuration.

           This is where LTTng stores the name of the Unix user’s current recording session
           between executions of lttng(1).  lttng-create(1) and lttng-set-session(1) set the
           current recording session.

       $LTTNG_HOME/lttng-traces
           Default output directory of LTTng traces in local and snapshot modes.

           Override this path with the --output option of the lttng-create(1) command.

       $LTTNG_HOME/.lttng
           Unix user’s LTTng runtime and configuration directory.

       $LTTNG_HOME/.lttng/sessions
           Default directory containing the Unix user’s saved recording session configurations
           (see lttng-save(1) and lttng-load(1)).

       /etc/lttng/sessions
           Directory containing the system-wide saved recording session configurations (see
           lttng-save(1) and lttng-load(1)).

       Note
           $LTTNG_HOME defaults to the value of the HOME environment variable.

EXAMPLES

       Example 1. Regenerate the metadata of the current recording session.

               $ lttng regenerate metadata

       Example 2. Regenerate the state dump event records of a specific recording session.

           See the --session option.

               $ lttng regenerate statedump --session=my-session

RESOURCES

       •   LTTng project website <https://lttng.org>

       •   LTTng documentation <https://lttng.org/docs>

       •   LTTng bug tracker <https://bugs.lttng.org>

       •   Git repositories <https://git.lttng.org>

       •   GitHub organization <https://github.com/lttng>

       •   Continuous integration <https://ci.lttng.org/>

       •   Mailing list <https://lists.lttng.org/> for support and development: lttng-
           dev@lists.lttng.org

       •   IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net

COPYRIGHT

       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.