Fix: lttng-ctl: lttng_list_sessions: initialize out_sessions to NULL when returning 0

[lttng-tools.git] / doc / man / lttng-regenerate.1.txt

lttng-regenerate(1)
===================
:revdate: 14 June 2021


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


SYNOPSIS
--------
Regenerate the metadata of a recording session:

[verse]
*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *regenerate metadata* [option:--session='SESSION']

Regenerate the state dump event records of a recording session:

[verse]
*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *regenerate statedump* [option:--session='SESSION']


DESCRIPTION
-----------
The `lttng regenerate` command regenerates specific data of:

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

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

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

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

See the ``<<examples,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 link:https://en.wikipedia.org/wiki/Network_Time_Protocol[NTP]
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 man: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 (nloption:--live option of
  man:lttng-create(1)).

* If it has user space channels, they're configured to use a
  per-user buffering scheme (nloption:--buffers-uid option of
  man:lttng-enable-channel(1)).
+
See man: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 (nloption:--snapshot option of the man:lttng-create(1)
command) or if LTTng rotates trace files for one of its channels (see
man:lttng-concepts(7)): in both cases, the state dump information may be
lost.


include::common-lttng-cmd-options-head.txt[]


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


include::common-lttng-cmd-help-options.txt[]


include::common-lttng-cmd-after-options.txt[]


[[examples]]
EXAMPLES
--------
.Regenerate the metadata of the current recording session.
====
[role="term"]
----
$ lttng regenerate metadata
----
====

.Regenerate the state dump event records of a specific recording session.
====
See the option:--session option.

[role="term"]
----
$ lttng regenerate statedump --session=my-session
----
====


include::common-footer.txt[]


SEE ALSO
--------
man:lttng(1),
man:lttng-concepts(7)