---
name: "lttng-start"
section: "1"
platform: "linux"
package: "lttng-tools"
version: "2.13.15-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/lttng-start"
---

# lttng-start(1)

Start an LTTng recording session

## NAME

lttng-start - Start an LTTng recording session

## SYNOPSIS

```
lttng [GENERAL OPTIONS] start [SESSION]
```

## DESCRIPTION

The **lttng start** command starts a recording session, that is, it activates the LTTng tracers for:

With the *SESSION* argument

The recording session named *SESSION*.

Without the *SESSION* argument

The current recording session (see [**lttng-concepts**(7)](/lttng-concepts/7.md) to learn more about the current recording session).

See [**lttng-concepts**(7)](/lttng-concepts/7.md) to learn more about recording sessions.

The selected recording session must be inactive (stopped). A recording session is inactive on creation (see [**lttng-create**(1)](/lttng-create/1.md)).

A **start-session** trigger action can also start a recording session (see [**lttng-add-trigger**(1)](/lttng-add-trigger/1.md)).

See the “EXAMPLES” section below for usage examples.

Stop an active recording session with the [**lttng-stop**(1)](/lttng-stop/1.md) command.

## OPTIONS

See [**lttng**(1)](/lttng/1.md) for *GENERAL OPTIONS*.

### 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.

## EXIT STATUS

**0**

Success

**1**

Command error

**2**

Undefined command

**3**

Fatal error

**4**

Command warning (something went wrong during the command)

## ENVIRONMENT

**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\_MAN\_BIN\_PATH**

Absolute path to the manual pager to use to read the LTTng command-line help (with [**lttng-help**(1)](/lttng-help/1.md) or with the **--help** option) instead of **/usr/bin/man**.

**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)](/lttng-sessiond/8.md)) to spawn from the [**lttng-create**(1)](/lttng-create/1.md) command.

The **--sessiond-path** general option overrides this environment variable.

## FILES

**$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/1.md). [**lttng-create**(1)](/lttng-create/1.md) and [**lttng-set-session**(1)](/lttng-set-session/1.md) 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)](/lttng-create/1.md) 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)](/lttng-save/1.md) and [**lttng-load**(1)](/lttng-load/1.md)).

**/etc/lttng/sessions**

Directory containing the system-wide saved recording session configurations (see [**lttng-save**(1)](/lttng-save/1.md) and [**lttng-load**(1)](/lttng-load/1.md)).

**Note**\

**$LTTNG\_HOME** defaults to the value of the **HOME** environment variable.

## EXAMPLES

**Example 1. Start the current recording session.**

```
$ lttng start
```

**Example 2. Start a specific recording session.**

```
$ lttng start my-session
```

## RESOURCES

• 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**

## COPYRIGHT

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.

## THANKS

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.

## SEE ALSO

[**lttng**(1)](/lttng/1.md), [**lttng-add-trigger**(1)](/lttng-add-trigger/1.md), [**lttng-create**(1)](/lttng-create/1.md), [**lttng-enable-event**(1)](/lttng-enable-event/1.md), [**lttng-stop**(1)](/lttng-stop/1.md), [**lttng-concepts**(7)](/lttng-concepts/7.md)