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[lttng-tools.git] / doc / man / lttng-create.1.txt

lttng-create(1)
===============
:revdate: 3 May 2021


NAME
----
lttng-create - Create an LTTng tracing session


SYNOPSIS
--------
Create a local mode tracing session:

[verse]
*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='DIR']
      [option:--no-output | option:--output='DIR' | option:--set-url=**file://**__DIR__]

Create a network streaming mode tracing session:

[verse]
*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='DIR']
      (option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL')

Create a snapshot mode tracing session:

[verse]
*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 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).

See man:lttng-concepts(7) to learn more about tracing sessions.

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 `/`.

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.

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.

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.

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 argument of the option:--set-url='URL', option:--ctrl-url='URL', and
option:--data-url='URL' options is an URL.

There are two available 'URL' formats.

Local format::
+
[verse]
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.

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}.

`net6`::
    TCP over IPv6.
+
The default values of 'CTRLPORT' and 'DATAPORT'
are respectively {default_network_control_port} and
{default_network_data_port}.

`tcp`::
    Same as the `net` protocol.
+
You may only use this with the option:--ctrl-url and option:--data-url
options together.

`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 TCP port.

'DATAPORT':::
    Data TCP port.

'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 selection
~~~~~~~~~~~~~~
See the <<modes,Tracing session modes>> section above.

At most one of:

option:--live[='DELAYUS']::
    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}.
+
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 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::
    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 'DIR', option:--output='DIR'::
    Equivalent to option:--set-url=++file://++__DIR__.

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 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:-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.

Network streaming and live modes:::
    Equivalent to using both the option:--ctrl-url and option:--data-url
    options.

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[]


include::common-cmd-footer.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-start(1),
man:lttng-status(1),
man:lttng-track(1),
man:lttng-concepts(7),
man:lttng-relayd(8),
man:lttng-sessiond(8)