lttng-create(1)
===============
+:revdate: 3 May 2021
NAME
SYNOPSIS
--------
-Normal mode:
+Create a local mode tracing session:
[verse]
-*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* [option:--output='PATH' | option:--no-output]
- [option:--shm-path='PATH'] ['SESSION']
+*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='DIR']
+ [option:--no-output | option:--output='DIR' | option:--set-url=**file://**__DIR__]
-Snapshot mode:
+Create a network streaming mode tracing session:
[verse]
-*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* option:--snapshot
- [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL']
- [option:--shm-path='PATH'] ['SESSION']
+*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='DIR']
+ (option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL')
-Live mode:
+Create a snapshot mode tracing session:
[verse]
-*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* option:--live[='DELAYUS']
- [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL']
- [option:--shm-path='PATH'] ['SESSION']
+*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] option:--snapshot [option:--shm-path='DIR']
+ [option:--no-output | option:--output='DIR' | option:--set-url='URL' |
+ option:--ctrl-url='URL' option:--data-url='URL']
+Create a live mode tracing session:
+
+[verse]
+*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] option:--live[='DELAYUS']
+ [option:--shm-path='DIR'] [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL']
DESCRIPTION
-----------
-The `lttng create` command creates a new tracing session.
+The `lttng create` command creates a new tracing session for your Unix
+user within the connected session daemon (see the ``Session daemon
+connection'' section of man:lttng(1) to learn how a user application
+connects to a session daemon).
-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.
+See man:lttng-concepts(7) to learn more about tracing sessions.
-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
-man:lttng-set-session(1) command can be used to set the current
-tracing session without manually editing the `.lttngrc` file.
+Without the 'SESSION' argument, LTTng automatically generates a tracing
+session name having the ++auto-++__YYYYmmdd__++-++__HHMMSS__ form, where
+'YYYYmmdd' and 'HHMMSS' are the creation date and time. 'SESSION' may
+:not: contain the character `/`.
-If 'SESSION' is omitted, a session name is automatically created having
-this form: `auto-YYYYmmdd-HHMMSS`. 'SESSION' *must not* contain the
-character `/`.
+Specify the path of the directory containing the shared memory files
+holding the channel ring buffers with the option:--shm-path option.
+Specifying a location on an NVRAM file system makes it possible to
+recover the latest recorded trace data when the system reboots after a
+crash with the man:lttng-crash(1) utility.
-The option:--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
-man:lttng-crash(1) utility.
+By default, the `create` command automatically spawns a session daemon
+for your Unix user if none is currently running. Override the path of
+the session daemon binary to spawn with the general
+genoption:--sessiond-path option. Avoid automatically spawning a session
+daemon with the general genoption:--no-sessiond option.
-Tracing sessions are destroyed using the man:lttng-destroy(1)
-command.
+On success, the `create` command sets the current tracing session (see
+man:lttng-concepts(7) to learn more) to the created tracing session.
+Show the status of the current tracing session with the
+man:lttng-status(1) command.
-Creation modes
-~~~~~~~~~~~~~~
-There are three tracing session modes:
-
-Normal mode::
- Traces the local system and writes the trace to the local
- file system. The option:--output option specifies the trace path.
- If omitted, the trace is written in the `$LTTNG_HOME/lttng-traces`
- directory (`$LTTNG_HOME` defaults to `$HOME`). The file system
- output can be disabled using the option:--no-output option.
-
-Snapshot mode::
- Traces the local system without writing the trace to the local file
- system (implicit option:--no-output option). Channels are automatically
- configured to be snapshot-ready on creation (see
- man:lttng-enable-channel(1)). The man:lttng-snapshot(1)
- command is used to take snapshots of the current ring buffers.
- The option:--set-url, or option:--ctrl-url and option:--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 man:lttng-relayd(8)). The
- option:--set-url, or option:--ctrl-url and option:--data-url options
- set the trace output destination. The live output URLs cannot use
- the `file://` protocol (see URL format below).
+List the tracing sessions of your Unix user, or of all users if
+your Unix user is `root`, within the connected session daemon with the
+man:lttng-list(1) command.
+
+Start and stop a tracing session with the man:lttng-start(1) and
+man:lttng-stop(1) commands.
+
+Save and load a tracing session with the man:lttng-save(1) and
+man:lttng-load(1) commands.
+
+Allow and disallow specific processes to record events with the
+man:lttng-track(1) and man:lttng-untrack(1) commands.
+
+Archive the current trace chunk of (rotate) a tracing session with the
+man:lttng-rotate(1) command.
+
+Destroy a tracing session with the man:lttng-destroy(1) command.
+
+
+[[modes]]
+Tracing session modes
+~~~~~~~~~~~~~~~~~~~~~
+As documented in man:lttng-concepts(7), LTTng offers four tracing
+session modes:
+
+[[local-mode]]Local mode::
+ Write the trace data to the local file system.
++
+The trace data output directory is:
++
+With the option:--no-output option:::
+ None: the file system output is disabled.
+
+With the option:--output='DIR' or option:--set-url=++file://++__DIR__ option:::
+ The directory 'DIR'.
+
+Otherwise:::
+ A subdirectory, under the `$LTTNG_HOME/lttng-traces` (`$LTTNG_HOME`
+ defaults to `$HOME`) directory, of which the name contains the
+ tracing session name and the date/time.
+
+[[network-streaming-mode]]Network streaming mode::
+ Send the trace data over the network to a listening relay daemon
+ (see man:lttng-relayd(8)).
++
+Set the trace output destination with the option:--set-url option, or
+with the option:--ctrl-url and option:--data-url options (see the
+<<url-format,URL format>> section below).
+
+[[snapshot-mode]]Snapshot mode (option:--snapshot option)::
+ Only write the trace data to the local file system or send it to a
+ listening relay daemon (man:lttng-relayd(8)) when LTTng takes a
+ snapshot (see the man:lttng-snapshot(1) command).
++
+With this mode, LTTng:
++
+With the option:--no-output option:::
+ Does :not: add any snapshot output to the created tracing
+ session.
+
+With the option:--output option, the option:--set-url option, or the option:--ctrl-url and option:--data-url options:::
+ Adds a snapshot output named `snapshot-1` using the provided
+ path or URL(s) to the created tracing session.
+
+Otherwise:::
+ Adds an automatic snapshot output named `snapshot-1` to the created
+ tracing session.
++
+The automatic snapshot output is a subdirectory, under the
+`$LTTNG_HOME/lttng-traces` (`$LTTNG_HOME` defaults to `$HOME`)
+directory, of which the name contains the tracing session name and the
+date/time.
+
+[[live-mode]]Live mode (option:--live option)::
+ Send the trace data over the network to a listening relay daemon
+ (see man:lttng-relayd(8)) for live reading.
++
+Set the trace output destination with the option:--set-url='URL' option,
+or with the option:--ctrl-url='URL' and option:--data-url='URL' options
+(see the <<url-format,URL format>> section below). 'URL' may :not: start
+with `file://`.
[[url-format]]
URL format
~~~~~~~~~~
-The option:--set-url, option:--ctrl-url, and option:--data-url options
-specify URLs.
+The argument of the option:--set-url='URL', option:--ctrl-url='URL', and
+option:--data-url='URL' options is an URL.
-The format of those URLs is one of:
+There are two available 'URL' formats.
+Local format::
++
[verse]
-file://'TRACEPATH'
-'NETPROTO'://('HOST' | 'IPADDR')[:__CTRLPORT__[:__DATAPORT__]][/'TRACEPATH']
-
-The `file://` protocol targets the *local file system*.
+file://'TRACEDIR'
+{nbsp}
++
+The `file://` protocol targets the *local file system*: you may only use
+such an URL with the option:--set-url option when you create the tracing
+session in local or snapshot mode (see the <<modes,Tracing session
+modes>> section above).
++
+'TRACEDIR':::
+ Absolute path to the directory containing the trace data on the
+ local file system.
-'TRACEPATH'::
- Absolute path to trace files on the local file system.
+Network format::
++
+[verse]
+'NETPROTO'://('HOST' | 'IPADDR')[:__CTRLPORT__[:__DATAPORT__]][/'TRACEDIR']
+{nbsp}
++
+This format is only available when you create the tracing session in
+network streaming, snapshot (option:--snapshot), or live (option:--live)
+mode (see the <<modes,Tracing session modes>> section above).
++
+'NETPROTO':::
+ Network protocol, amongst:
++
+--
+`net`::
+ TCP over IPv4.
++
+The default values of 'CTRLPORT' and 'DATAPORT'
+are respectively {default_network_control_port} and
+{default_network_data_port}.
-The other version is used for *network streaming*.
+`net6`::
+ TCP over IPv6.
++
+The default values of 'CTRLPORT' and 'DATAPORT'
+are respectively {default_network_control_port} and
+{default_network_data_port}.
-'NETPROTO'::
- Network protocol, amongst:
+`tcp`::
+ Same as the `net` protocol.
+
-* `net`: TCP over IPv4; the default values of `<ctrl port>` and
- `<data port>` are resp. 5342 and 5343
-* `net6`: TCP over IPv6: same default ports as `net` protocol
-* `tcp`: same as `net` protocol; can only be used with the
- option:--ctrl-url and option:--data-url options together
-* `tcp6`: same as `net6` protocol; can only be used with the
- option:--ctrl-url and option:--data-url options together
+You may only use this with the option:--ctrl-url and option:--data-url
+options together.
-('HOST' | 'IPADDR')::
- Hostname or IP address (IPv6 address *must* be enclosed in brackets
- (`[` and `]`); see https://www.ietf.org/rfc/rfc2732.txt[RFC 2732]).
+`tcp6`::
+ Same as the `net6` protocol.
++
+You can only be use this with the option:--ctrl-url and
+option:--data-url options together.
+--
++
+('HOST' | 'IPADDR'):::
+ Hostname or IP address.
++
+IPv6 address must be enclosed in square brackets (`[` and{nbsp}`]`);
+see https://www.ietf.org/rfc/rfc2732.txt[RFC{nbsp}2732].
-'CTRLPORT'::
- Control port.
+'CTRLPORT':::
+ Control TCP port.
-'DATAPORT'::
- Data port.
+'DATAPORT':::
+ Data TCP 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 man:lttng-relayd(8).
+'TRACEDIR':::
+ Path of the directory containing the trace data on the remote file
+ system.
++
+This path is relative to the base output directory of the LTTng relay
+daemon (see the nloption:--output option of man:lttng-relayd(8)).
include::common-cmd-options-head.txt[]
-Mode
-~~~~
+Mode selection
+~~~~~~~~~~~~~~
+See the <<modes,Tracing session modes>> section above.
+
+At most one of:
+
option:--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 option:--set-url, or option:--ctrl-url and option:--data-url)
- and must have a relay daemon listening (see man:lttng-relayd(8)).
+ Create the tracing session in live mode.
++
+The optional 'DELAYUS' argument is the maximum time (in µs) you can wait
+for the data to be flushed (sent to the connected LTTng relay daemon).
+The default value of 'DELAYUS' is {default_lttng_live_timer}.
+
-By default, 'DELAYUS' is 1000000 and the network URL is set to
-`net://127.0.0.1`.
+Set the URL of the relay daemon to connect to with the option:--set-url
+option, or with the option:--ctrl-url and option:--data-url options,
+instead of using `net://127.0.0.1`.
++
+The session daemon must be able to connect to a listening relay daemon
+(see man:lttng-relayd(8)).
option:--snapshot::
- Create the session in snapshot mode. This is the equivalent of using
- the option:--no-output option and creating all the channels of this
- new tracing session in overwrite mode with an `mmap` output type.
+ Create the tracing session in snapshot mode.
++
+This is equivalent to:
++
+* One of:
++
+--
+With the option:--no-output option::
+ Not adding any snapshot output after LTTng creates the tracing
+ session.
+
+With the option:--output option, the option:--set-url option, or the option:--ctrl-url and option:--data-url options::
+ Adding a snapshot output named `snapshot-1` using the provided path
+ or URL(s) immediately after LTTng creates the tracing session.
+
+Otherwise::
+ Adding an automatic snapshot output named `snapshot-1` immediately
+ after LTTng creates the tracing session.
++
+The automatic snapshot output is a subdirectory, under the
+`$LTTNG_HOME/lttng-traces` (`$LTTNG_HOME` defaults to `$HOME`)
+directory, of which the name contains the tracing session name and the
+date/time.
+--
+
+* Forcing all the channels to be created for the tracing session to be
+ configured with the nloption:--override and nloption:--output=++mmap++
+ options (see man:lttng-enable-channel(1)).
Output
~~~~~~
option:--no-output::
- Do not output any trace data.
+ Depending on the tracing session mode (see the <<modes,Tracing
+ session modes>> section above):
++
+Local mode:::
+ Disable the file system output.
+
+Snapshot mode (option:--snapshot option):::
+ Do :not: add a snapshot output after creating the tracing session.
-option:-o, option:--output='PATH'::
- Set trace output path to 'PATH'.
+option:-o 'DIR', option:--output='DIR'::
+ Equivalent to option:--set-url=++file://++__DIR__.
-option:--shm-path='PATH'::
- Create shared memory holding buffers at 'PATH'.
+option:--shm-path='DIR'::
+ Set the path of the directory containing the shared memory files
+ holding the channel ring buffers to 'DIR' on the local file sytem.
URL
~~~
-See the <<url-format,URL format>> section above for more information
-about the syntax of the following options' 'URL' argument.
+See the <<url-format,URL format>> section above to learn more about the
+syntax of the 'URL' argument of the following options.
+
+option:-C 'URL', option:--ctrl-url='URL'::
+ Set the control path URL to 'URL'.
++
+You must also use the option:--data-url option.
++
+Not available in local mode (see the <<modes,Tracing session modes>>
+section above).
++
+In snapshot mode, this is equivalent to using the nloption:--ctrl-url
+option of the `add-output` action of the man:lttng-snapshot(1) command
+immediately after creating the tracing session.
-option:-C, option:--ctrl-url='URL'::
- Set control path URL to 'URL' (must use option:--data-url option
- also).
+option:-D 'URL', option:--data-url='URL'::
+ Set the trace data path URL to 'URL'.
++
+You must also use the option:--ctrl-url option.
++
+Not available in local mode (see the <<modes,Tracing session modes>>
+section above).
++
+In snapshot mode, this is equivalent to using the nloption:--data-url
+option of the `add-output` action of the man:lttng-snapshot(1) command
+immediately after creating the tracing session.
+
+option:-U 'URL', option:--set-url='URL'::
+ Set the destination URL of the control path and trace data to 'URL'.
++
+This URL remains unchanged as long as the tracing session exists.
++
+Depending on the tracing session mode (see the <<modes,Tracing session
+modes>> section above):
++
+Local mode:::
+ 'URL' must start with `file://`, followed with the destination
+ directory path on the local file system.
-option:-D, option:--data-url='URL'::
- Set data path URL to 'URL' (must use option:--ctrl-url option
- also).
+Network streaming and live modes:::
+ Equivalent to using both the option:--ctrl-url and option:--data-url
+ options.
-option:-U, option:--set-url='URL'::
- Set URL destination of the trace data to 'URL'. It is persistent for
- the session lifetime. This option sets both data
- (option:--data-url option) and control (option:--ctrl-url option)
- URLs at the same time.
+Snapshot mode (option:--snapshot option):::
+ Equivalent to using the 'URL' non-option argument of the
+ `add-output` action of the man:lttng-snapshot(1) command immediately
+ after creating the tracing session.
include::common-cmd-help-options.txt[]
SEE ALSO
--------
+man:lttng(1),
man:lttng-destroy(1),
+man:lttng-enable-channel(1),
+man:lttng-list(1),
+man:lttng-rotate(1),
+man:lttng-save(1),
man:lttng-set-session(1),
-man:lttng(1)
+man:lttng-start(1),
+man:lttng-status(1),
+man:lttng-track(1),
+man:lttng-concepts(7),
+man:lttng-relayd(8),
+man:lttng-sessiond(8)
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