|
HTML rendering created 2026-09-09 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. |
|
|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | ENVIRONMENT | FILES | EXAMPLES | RESOURCES | COPYRIGHT | THANKS | SEE ALSO | COLOPHON |
|
|
|
LTTNG-SNAPSHOT(1) LTTng Manual LTTNG-SNAPSHOT(1)
lttng-snapshot - Take a snapshot of an LTTng recording session
Take a recording session snapshot:
lttng [GENERAL OPTIONS] snapshot record [--max-size=SIZE]
[--name=NAME] [--session=SESSION]
[--ctrl-url=URL --data-url=URL | URL]
Add a snapshot output to a recording session:
lttng [GENERAL OPTIONS] snapshot add-output [--max-size=SIZE]
[--name=NAME] [--session=SESSION]
(--ctrl-url=URL --data-url=URL | URL)
Show the snapshot output of a recording session:
lttng [GENERAL OPTIONS] snapshot list-output [--session=SESSION]
Remove the snapshot output from a recording session:
lttng [GENERAL OPTIONS] snapshot del-output [--session=SESSION] 1
The lttng snapshot command can take a snapshot of, add or remove a
snapshot output, and show the snapshot output 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.
A snapshot is a dump of the current sub-buffers of all the
channels of the selected recording session.
When LTTng takes a snapshot, it sends the sub-buffer dump of the
selected recording session to the local file system or over the
network to a listening relay daemon (lttng-relayd(8)). See the
“Snapshot output” section below to learn more.
When LTTng takes a snapshot, it does NOT clear the sub-buffers of
the selected recording session. In other words, different
snapshots of the selected recording session can contain the same
event records.
You must have created the selected recording session in snapshot
mode (see the --snapshot option of the lttng-create(1) command as
well as lttng-concepts(7) to learn more about recording session
modes) to use the snapshot command.
A snapshot-session trigger action can also take a recording
session snapshot (see lttng-add-trigger(1)).
See the “EXAMPLES” section below for usage examples.
If you want, instead, to keep all the trace data, but divide it
into archived chunks which are then, like snapshots, ready to be
processed, see the recording session rotation feature in
lttng-concepts(7). Trace chunk archives do NOT overlap like
snapshots can.
Note
Before you take a snapshot on a system with a high event
throughput, the LTTng project recommends that you first run
the lttng-stop(1) command. Otherwise, the snapshot could
contain “holes”, the result of the tracers overwriting
unconsumed trace packets during the snapshot operation.
After LTTng writes the snapshot trace data, you can restart
the recording session with the lttng-start(1) command.
Snapshot output
When you take a recording session snapshot with the record action,
LTTng writes the snapshot trace files to:
If you specify the URL non-option argument or the --ctrl-url and
--data-url options
The output defined by the URL non-option argument or by the
arguments of the options.
See lttng-create(1) for the format of URL.
Otherwise
The snapshot output of the selected recording session.
Add a snapshot output to a recording session with the add-
output action. As of LTTng 2.15.1, you may only add one
snapshot output to a given recording session.
When you create a snapshot mode recording session with the
--snapshot option of the lttng-create(1) command, and without
its --no-output option, the create command automatically adds
a snapshot output named snapshot-1 to the created recording
session:
With its --output, --set-url, --ctrl-url, or --data-url
options
Equivalent to using the add-output action with the
provided or equivalent URL(s) immediately after creating
the recording session.
Otherwise
A subdirectory, under the $LTTNG_HOME/lttng-traces
($LTTNG_HOME defaults to $HOME) directory, of which the
name contains the recording session name and the
date/time.
Show the current snapshot output of a recording session with
the list-output action.
Remove the snapshot output of a recording session with the
del-output action.
For both the record and add-output actions:
• Assign a name to a snapshot output with the --name=NAME
option.
NAME becomes part of the snapshot trace file names which LTTng
sends to this output.
• By default, the snapshot files can be as big as the sum of the
sizes of all the sub-buffers of all the channels of the
selected recording session.
Set the maximum total size of all the snapshot trace files
LTTng writes with the --max-size option.
See lttng(1) for GENERAL OPTIONS.
Recording target
-s SESSION, --session=SESSION
Take a snapshot of the sub-buffers of the recording session
named SESSION instead of the current recording session.
Output
See the “Snapshot output” section above.
-C URL, --ctrl-url=URL
Set the control path URL to URL.
You must also use the --data-url option.
See lttng-create(1) for the format of URL.
-D URL, --data-url=URL
Set the trace data path URL to URL.
You must also use the --ctrl-url option.
See lttng-create(1) for the format of URL.
-m SIZE, --max-size=SIZE
Set the maximum total size of all the snapshot trace files
LTTng writes when taking 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 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.
0
Success
1
Command error
2
Undefined command
3
Fatal error
4
Command warning (something went wrong during the command)
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_LIST_LEGACY
Set to 1 to use the legacy output format (LTTng 2.14 and
earlier) for the lttng-list(1) command instead of the modern
output format.
Note that the legacy output doesn’t show anything related to
features introduced after LTTng 2.14.
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_NO_UTF_8
Set to 1 to NOT emit multi-byte UTF-8 sequences, even if the
locale claims to support it.
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.
LTTNG_TERM_COLOR
Controls when to emit terminal SGR codes in the output.
The NO_COLOR environment variable overrides this.
One of:
auto (default)
Only emit SGR codes when the standard output is connected
to a color-capable terminal.
always
Always emit SGR codes.
never
Never emit SGR codes.
NO_COLOR
If set and not empty, then it’s equivalent to setting
LTTNG_TERM_COLOR to never.
See NO_COLOR <https://no-color.org/> to learn more.
$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)).
/usr/local/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.
Example 1. Take a snapshot of the current recording session,
sending the trace files to its snapshot output.
$ lttng snapshot record
Example 2. Take a snapshot of a specific recording session, giving
it a custom name.
See the --session and --name options.
$ lttng snapshot record --session=my-session --name=SNAP
Example 3. Take a snapshot of the current recording session,
sending the trace files to a custom location.
See the “Output directory” section of lttng-relayd(8) to
understand where the relay daemon to connect to (3.96.87.215)
writes the received traces.
$ lttng snapshot record net://3.96.87.215
Example 4. Replace the snapshot output of a specific recording
session with a local file system path.
See the --session option.
$ lttng snapshot del-output --session=monk 1
$ lttng snapshot add-output --session=monk \
file:///path/to/snapshots
Example 5. Take a snapshot of the current recording session,
making sure its size is not over 4 MiB.
See the --max-size option.
$ lttng snapshot record --max-size=4M
• 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
• Mastodon <https://mastodon.social/@lttng>
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(1), lttng-create(1), lttng-concepts(7)
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
⟨https://github.com/lttng/lttng-tools.git⟩ on 2026-08-04. (At
that time, the date of the most recent commit that was found in
the repository was 2026-07-30.) 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 2.15.1 14 June 2021 LTTNG-SNAPSHOT(1)
Pages that refer to this page: lttng(1), lttng-add-trigger(1), lttng-create(1), lttng-rotate(1), lttng-concepts(7)
|
HTML rendering created 2026-09-09 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. |
|