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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-CREATE(1) LTTng Manual LTTNG-CREATE(1)
lttng-create - Create an LTTng tracing session
Local mode:
lttng [GENERAL OPTIONS] create [SESSION] [--shm-path=PATH]
[--no-output | --output=PATH | --set-url=file://PATH]
Network streaming mode:
lttng [GENERAL OPTIONS] create [SESSION] [--shm-path=PATH]
(--set-url=URL | --ctrl-url=URL --data-url=URL)
Snapshot mode:
lttng [GENERAL OPTIONS] create [SESSION] --snapshot
[--shm-path=PATH] [--set-url=URL | --ctrl-url=URL --data-url=URL]
Live mode:
lttng [GENERAL OPTIONS] create [SESSION] --live[=DELAYUS]
[--shm-path=PATH] [--set-url=URL | --ctrl-url=URL --data-url=URL]
The lttng create command creates a new tracing session.
A tracing session is a named container of channels, which in turn
contain event rules. It is domain-agnostic, in that channels and
event rules can be enabled for the user space tracer and/or the
Linux kernel tracer.
On execution, an .lttngrc file is created, if it does not exist,
in the user’s home directory. This file contains the name of the
current tracing session. When creating a new tracing session with
lttng create, the current tracing session is set to this new
tracing session. The lttng-set-session(1) command can be used to
set the current tracing session without manually editing the
.lttngrc file.
If SESSION is omitted, a session name is automatically created
having this form: auto-YYYYmmdd-HHMMSS. SESSION must not contain
the character /.
The --shm-path option can be used to specify the path to the
shared memory holding the ring buffers. Specifying a location on
an NVRAM file system makes it possible to retrieve the latest
recorded trace data when the system reboots after a crash. To view
the events of ring buffer files after a system crash, use the
lttng-crash(1) utility.
Tracing sessions are destroyed using the lttng-destroy(1) command.
Creation modes
There are four tracing session modes:
Local mode
Traces the local system and writes the trace to the local file
system. The --output option specifies the trace path. Using
--set-url=file://PATH is the equivalent of using
--output=PATH. The file system output can be disabled using
the --no-output option.
If none of the options mentioned above are used, then the
trace is written locally in the $LTTNG_HOME/lttng-traces
directory ($LTTNG_HOME defaults to $HOME).
Network streaming mode
Traces the local system and sends the trace over the network
to a listening relay daemon (see lttng-relayd(8)). The --set-
url, or --ctrl-url and --data-url options set the trace output
destination (see the URL format section below).
Snapshot mode
Traces the local system without writing the trace to the local
file system (implicit --no-output option). Channels are
automatically configured to be snapshot-ready on creation (see
lttng-enable-channel(1)). The lttng-snapshot(1) command is
used to take snapshots of the current ring buffers. The --set-
url, or --ctrl-url and --data-url options set the default
snapshot output destination.
Live mode
Traces the local system, sending trace data to an LTTng relay
daemon over the network (see lttng-relayd(8)). The --set-url,
or --ctrl-url and --data-url options set the trace output
destination. The live output URLs cannot use the file://
protocol (see the URL format section below).
URL format
The --set-url, --ctrl-url, and --data-url options' arguments are
URLs.
The format of those URLs is one of:
file://TRACEPATH
NETPROTO://(HOST | IPADDR)[:CTRLPORT[:DATAPORT]][/TRACEPATH]
The file:// protocol targets the local file system and can only be
used as the --set-url option’s argument when the session is
created in local or snapshot mode.
TRACEPATH
Absolute path to trace files on the local file system.
The other version is available when the session is created in
network streaming, snapshot, or live mode.
NETPROTO
Network protocol, amongst:
net
TCP over IPv4; the default values of CTRLPORT and DATAPORT
are respectively 5342 and 5343.
net6
TCP over IPv6: same default ports as the net protocol.
tcp
Same as the net protocol; can only be used with the
--ctrl-url and --data-url options together.
tcp6
Same as the net6 protocol; can only be used with the
--ctrl-url and --data-url options together.
(HOST | IPADDR)
Hostname or IP address (IPv6 address must be enclosed in
brackets ([ and ]); see RFC 2732
<https://www.ietf.org/rfc/rfc2732.txt>).
CTRLPORT
Control port.
DATAPORT
Data port.
TRACEPATH
Path of trace files on the remote file system. This path is
relative to the base output directory set on the relay daemon
side; see lttng-relayd(8).
General options are described in lttng(1).
Mode selection
--live[=DELAYUS]
Create the session in live mode.
The optional DELAYUS parameter, given in microseconds, is the
maximum time the user can wait for the data to be flushed.
This mode can be set with a network URL (options --set-url, or
--ctrl-url and --data-url) and must have a relay daemon
listening (see lttng-relayd(8)).
By default, DELAYUS is 1000000 and the network URL is set to
net://127.0.0.1.
--snapshot
Create the session in snapshot mode. This is the equivalent of
using the --no-output option and creating all the channels of
this new tracing session in overwrite mode with an mmap output
type.
Output
--no-output
In local mode, do not output any trace data.
-o PATH, --output=PATH
In local mode, set trace output path to PATH.
--shm-path=PATH
Create shared memory holding buffers at PATH.
URL
See the URL format section above for more information about the
syntax of the following options' URL argument.
-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).
-U URL, --set-url=URL
Set URL destination of the trace data to URL. It is persistent
for the session lifetime. This option sets both data (--data-
url option) and control (--ctrl-url option) URLs at the same
time.
In local mode, URL must start with file:// followed by the
destination path on the local file system.
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: [email protected]
• 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:[email protected]>.
lttng-destroy(1), lttng-set-session(1), 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 [email protected]. 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
[email protected]
LTTng 2.12.0-pre 10/29/2018 LTTNG-CREATE(1)
Pages that refer to this page: lttng(1), lttng-add-context(1), lttng-calibrate(1), lttng-create(1), lttng-destroy(1), lttng-disable-channel(1), lttng-disable-event(1), lttng-disable-rotation(1), lttng-enable-channel(1), lttng-enable-event(1), lttng-enable-rotation(1), lttng-help(1), lttng-list(1), lttng-load(1), lttng-metadata(1), lttng-regenerate(1), lttng-rotate(1), lttng-save(1), lttng-set-session(1), lttng-snapshot(1), lttng-start(1), lttng-status(1), lttng-stop(1), lttng-track(1), lttng-untrack(1), lttng-version(1), lttng-view(1), babeltrace2-source.ctf.lttng-live(7), lttng-sessiond(8)
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HTML rendering created 2025-09-06 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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