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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT VARIABLES | FILES | EXIT STATUS | BUGS | RESOURCES | COPYRIGHTS | THANKS | AUTHORS | SEE ALSO | COLOPHON |
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LTTNG-SNAPSHOT(1) LTTng Manual LTTNG-SNAPSHOT(1)
lttng-snapshot - Take LTTng snapshots and configure snapshot
outputs
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)
The lttng snapshot command manages the snapshot outputs and takes
snapshots.
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.
Note
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)).
General options are described in lttng(1).
Target
-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
also).
-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-options
List available command options.
LTTNG_ABORT_ON_ERROR
Set to 1 to abort the process after the first error is
encountered.
LTTNG_HOME
Overrides the $HOME environment variable. Useful when the
user running the commands has a non-writable home directory.
LTTNG_MAN_BIN_PATH
Absolute path to the man pager to use for viewing help
information about LTTng commands (using lttng-help(1) or
lttng COMMAND --help).
LTTNG_SESSION_CONFIG_XSD_PATH
Path in which the session.xsd session configuration XML
schema may be found.
LTTNG_SESSIOND_PATH
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.
$LTTNG_HOME/.lttngrc
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.
$LTTNG_HOME/lttng-traces
Default output directory of LTTng traces. This can be
overridden with the --output option of the lttng-create(1)
command.
$LTTNG_HOME/.lttng
User LTTng runtime and configuration directory.
$LTTNG_HOME/.lttng/sessions
Default location of saved user tracing sessions (see
lttng-save(1) and lttng-load(1)).
/usr/local/etc/lttng/sessions
System-wide location of saved tracing sessions (see
lttng-save(1) and lttng-load(1)).
Note
$LTTNG_HOME defaults to $HOME when not explicitly set.
0
Success
1
Command error
2
Undefined command
3
Fatal error
4
Command warning (something went wrong during the command)
If you encounter any issue or usability problem, please report it
on the LTTng bug tracker <https://bugs.lttng.org/projects/lttng-
tools>.
• LTTng project website <https://lttng.org>
• LTTng documentation <https://lttng.org/docs>
• Git repositories <http://git.lttng.org>
• GitHub organization <http://github.com/lttng>
• Continuous integration <http://ci.lttng.org/>
• Mailing list <http://lists.lttng.org> for support and
development: lttng-dev@lists.lttng.org
• IRC channel <irc://irc.oftc.net/lttng>: #lttng on
irc.oftc.net
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.
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.
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
<mailto:jeremie.galarneau@efficios.com>.
lttng(1)
This page is part of the LTTng-Tools ( LTTng tools) project.
Information about the project can be found at
⟨http://lttng.org/⟩. It is not known how to report bugs for this
man page; if you know, please send a mail to man-pages@man7.org.
This page was obtained from the project's upstream Git repository
⟨git://git.lttng.org/lttng-tools.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
man-pages@man7.org
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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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