--- name: "lttng-track" section: "1" platform: "linux" package: "lttng-tools" version: "2.13.15-2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/lttng-track" --- # lttng-track(1) Allow specific processes to record LTTng events ## NAME lttng-track - Allow specific processes to record LTTng events ## SYNOPSIS Allow specific processes to record Linux kernel events: ``` lttng [GENERAL OPTIONS] track --kernel [--session=SESSION] (--pid=PID[,PID]... | --vpid=VPID[,VPID]... | --uid=UID[,UID]... | --vuid=VUSER[,VUSER]... | --gid=GID[,GID]... | --vgid=VGROUP[,VGROUP]...)... ``` ``` lttng [GENERAL OPTIONS] track --kernel [--session=SESSION] --all (--pid | --vpid | --uid | --vuid | --gid | --vgid)... ``` Allow specific processes to record user space events: ``` lttng [GENERAL OPTIONS] track --userspace [--session=SESSION] (--vpid=VPID[,VPID]... | --vuid=VUSER[,VUSER]... | --vgid=VGROUP[,VGROUP]...)... ``` ``` lttng [GENERAL OPTIONS] track --userspace [--session=SESSION] --all (--vpid | --vgid | --vuid)... ``` ## DESCRIPTION The **lttng track** command allows one or more processes to record LTTng events based on their attributes within: With the **--session**=*SESSION* option The recording session named *SESSION*. Without the **--session** option 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 and recording event rules. The **track** command adds values to *inclusion sets* of process attributes. The available inclusion sets are, for a given recording session: With the **--kernel** option • Process ID (PID). • Virtual process ID (VPID). This is the PID as seen by the application. • Unix user ID (UID). • Virtual Unix user ID (VUID). This is the UID as seen by the application. • Unix group ID (GID). • Virtual Unix group ID (VGID). This is the GID as seen by the application. With the **--userspace** option • VPID • VUID • VGID When an event *E* satisfies all the other explicit and implicit conditions of an event rule *ER*, *ER* matches *E* if the attributes of the process for which LTTng creates *E* are **all** part of the inclusion sets of the recording session and domain of *ER*. By default, on recording session creation (see [**lttng-create**(1)](/lttng-create/1.md)), all processes are allowed to record events. In other words, all the inclusion sets of the recording session contain all the possible process attribute values. If a given inclusion set *IS* contains all the possible values (**--all** option), then using the **track** command to add one or more values *V* to *IS*: 1\. Removes all the values from *IS*. This effectively makes *IS* empty. 2\. Adds *V* to *IS*. Example: with the PID inclusion set, you can record all the system calls of a given process: ``` $ lttng enable-event --kernel --all --syscall $ lttng track --kernel --pid=2345 $ lttng start ``` See the “EXAMPLES” section below for usage examples. Remove values from an inclusion set with the [**lttng-untrack**(1)](/lttng-untrack/1.md) command. ### Inclusion set example This example operates on the Linux kernel process ID (PID) inclusion set of the current recording session to show how an inclusion set works. Assume the maximum system PID is 7 for this example. 1\. Initial inclusion set: ``` [0] [1] [2] [3] [4] [5] [6] [7] ``` 2\. Command: ``` $ lttng track --kernel --pid=3,6,7 ``` Inclusion set is now: ``` [ ] [ ] [ ] [3] [ ] [ ] [6] [7] ``` 3\. Command: ``` $ lttng untrack --kernel --pid=7 ``` Inclusion set is now: ``` [ ] [ ] [ ] [3] [ ] [ ] [6] [ ] ``` 4\. Command: ``` $ lttng track --kernel --pid=1,5 ``` Inclusion set is now: ``` [ ] [1] [ ] [3] [ ] [5] [6] [ ] ``` Remove values from an inclusion set with the [**lttng-untrack**(1)](/lttng-untrack/1.md) command. ## OPTIONS See [**lttng**(1)](/lttng/1.md) for *GENERAL OPTIONS*. ### Tracing domain One of: - **-k**, **--kernel** Add values to one or more Linux kernel inclusion sets. - **-u**, **--userspace** Add values to one or more user space inclusion sets. ### Recording target - **-s** *SESSION*, **--session**=*SESSION* Add values to one or more inclusion sets of the recording session named *SESSION* instead of the current recording session. ### Inclusion set selection **-p** \[*PID*\[,*PID*\]...\], **--pid**\[=*PID*\[,*PID*\]...\] For each *PID* argument, add *PID* to the process ID inclusion set of the selected recording session and domain. *PID* is the process ID attribute of a process as seen from the root PID namespace (see [**pid\_namespaces**(7)](/pid_namespaces/7.md)). Only available with **--kernel** option. **--vpid**\[=*VPID*\[,*VPID*\]...\] For each *VPID* argument, add *VPID* to the virtual process ID inclusion set of the selected recording session and domain. *VPID* is the virtual process ID attribute of a process as seen from the PID namespace of the process (see [**pid\_namespaces**(7)](/pid_namespaces/7.md)). **--uid**\[=*USER*\[,*USER*\]...\] For each *USER* argument, add *USER* to the user ID inclusion set of the selected recording session and domain. *USER* is either: • The real user ID (see **getuid**(3)) of a process as seen from the root user namespace (see [**user\_namespaces**(7)](/user_namespaces/7.md)). • A user name. The connected LTTng session daemon (see [**lttng-sessiond**(8)](/lttng-sessiond/8.md)) performs the user name resolution on addition to the user ID inclusion set. Only available with **--kernel** option. **--vuid**\[=*VUSER*\[,*VUSER*\]...\] For each *VUSER* argument, add *VUSER* to the virtual user ID inclusion set of the selected recording session and domain. *VUSER* is either: • The real user ID (see **getuid**(3)) of a process as seen from the user namespace (see [**user\_namespaces**(7)](/user_namespaces/7.md)). • A user name. The connected LTTng session daemon (see [**lttng-sessiond**(8)](/lttng-sessiond/8.md)) performs the user name resolution on addition to the virtual user ID inclusion set. **--gid**\[=*GROUP*\[,*GROUP*\]...\] For each *GROUP* argument, add *GROUP* to the group ID inclusion set of the selected recording session and domain. *GROUP* is either: • The real group ID (see **getgid**(3)) of a process as seen from the root user namespace (see [**user\_namespaces**(7)](/user_namespaces/7.md)). • A group name. The connected LTTng session daemon (see [**lttng-sessiond**(8)](/lttng-sessiond/8.md)) performs the group name resolution on addition to the group ID inclusion set. Only available with **--kernel** option. **--vgid**\[=*VGROUP*\[,*VGROUP*\]...\] For each *VGROUP* argument, add *VGROUP* to the virtual group ID inclusion set of the selected recording session and domain. *VGROUP* is either: • The real group ID (see **getgid**(3)) of a process as seen from the user namespace (see [**user\_namespaces**(7)](/user_namespaces/7.md)). • A group name. The connected LTTng session daemon (see [**lttng-sessiond**(8)](/lttng-sessiond/8.md)) performs the group name resolution on addition to the virtual group ID inclusion set. ### Inclusion set operation - **-a**, **--all** With one or more empty **--pid**, **--vpid**, **--uid**, **--vuid**, **--gid**, and **--vgid** options: add **all** the possible values to the selected inclusion sets. ### 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. Add the PIDs 1728 and 3775 to the Linux kernel process ID inclusion set of the current recording session.** See the **--pid** option. ``` $ lttng track --kernel --pid=1728,3775 ``` **Example 2. Add the ID of a specific user to the user space virtual user ID inclusion set of a specific recording session.** See the **--vuid** and **--session** options. ``` $ lttng track --userspace --session=my-session --vuid=http ``` **Example 3. Add all the possible group IDs to the Linux kernel group ID inclusion set of the current recording session.** See the **--all** and **--gid** options. ``` $ lttng track --kernel --all --gid ``` ## RESOURCES • LTTng project website \ • LTTng documentation \ • LTTng bug tracker \ • Git repositories \ • GitHub organization \ • Continuous integration \ • Mailing list \ for support and development: **lttng-dev@lists.lttng.org** • IRC channel \: **#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 \. See the **LICENSE** \ file for details. ## THANKS Special thanks to Michel Dagenais and the DORSAL laboratory \ 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-untrack**(1)](/lttng-untrack/1.md), [**lttng-concepts**(7)](/lttng-concepts/7.md)