X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=doc%2Fman%2Flttng-regenerate.1.txt;fp=doc%2Fman%2Flttng-regenerate.1.txt;h=d3f645fc6d9e381066679a9723767a491d0e3e67;hp=a220551884e192e477e2c588f87164efe1e585b5;hb=26f0c7794376456fcb5b13d4eae91c0ccf0dfe66;hpb=65750bcdda3dd71b72683573d35a662c0b467a8f diff --git a/doc/man/lttng-regenerate.1.txt b/doc/man/lttng-regenerate.1.txt index a22055188..d3f645fc6 100644 --- a/doc/man/lttng-regenerate.1.txt +++ b/doc/man/lttng-regenerate.1.txt @@ -1,56 +1,87 @@ lttng-regenerate(1) =================== -:revdate: 18 January 2018 +:revdate: 30 April 2021 NAME ---- -lttng-regenerate - Manage an LTTng tracing session's data regeneration +lttng-regenerate - Regenerate specific data of an LTTng tracing session SYNOPSIS -------- -Regenerate the metadata of a session: +Regenerate the metadata of a tracing session: [verse] *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *regenerate metadata* [option:--session='SESSION'] -Regenerate the state dump of a session: +Regenerate the state dump event records of a tracing session: [verse] *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *regenerate statedump* [option:--session='SESSION'] + DESCRIPTION ----------- -The `lttng regenerate` command regenerates specific data of a tracing session. - -As of this version, the `metadata` and `statedump` actions are -available. +The `lttng regenerate` command regenerates specific data of: +With the option:--session='SESSION' option:: + The tracing session named 'SESSION'. -Regenerating a tracing session's metadata -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The `lttng regenerate metadata` action can be used to resample the offset -between the system's monotonic clock and the wall-clock time. +Without the option:--session option:: + The current tracing session (see man:lttng-concepts(7) to learn more + about the current tracing session). -This action is meant to be used to resample the wall-clock time following a -major link:https://en.wikipedia.org/wiki/Network_Time_Protocol[NTP] correction. -As such, a system booting with an incorrect wall time can be traced before its -wall time is NTP-corrected. Regenerating the tracing session's metadata ensures -that trace viewers can accurately determine the events time relative to Unix -Epoch. +See man:lttng-concepts(7) to learn more about tracing sessions. -If you use man:lttng-rotate(1) or man:lttng-enable-rotation(1) to make -tracing session rotations, this action regenerates the current and -next trace chunks's metadata files. +As of this version, the `metadata` and `statedump` targets are +available. -Regenerating a tracing session's state dump -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The `lttng regenerate statedump` action can be used to collect up-to-date state -dump information during the tracing session. This is particularly useful in -snapshot (see man:lttng-snapshot(1)) or trace file rotation (see -man:lttng-enable-channel(1)) modes where the state dump information may be +Regenerate the metadata of a tracing 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 tracing 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 tracing 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 +tracing 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 tracing 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 tracing 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. @@ -58,27 +89,17 @@ include::common-cmd-options-head.txt[] option:-s 'SESSION', option:--session='SESSION':: - Regenerate the data of the tracing session named 'SESSION' + Regenerate specific data of the tracing session named 'SESSION' instead of the current tracing session. include::common-cmd-help-options.txt[] -LIMITATIONS ------------ -The `lttng regenerate metadata` command can only be used on kernel and -user space tracing sessions (using per-user buffering), in non-live -mode. - -See man:lttng-enable-channel(1) for more information about -buffering schemes and man:lttng-create(1) for more information -about the different tracing session modes. - - include::common-cmd-footer.txt[] SEE ALSO -------- -man:lttng(1) +man:lttng(1), +man:lttng-concepts(7)