LTTNG-UNTRACK(1)

📦
version 2.15.1 · 12 versions
, in ubuntu stonking

💅 lttng-untrack 💅 (from the LTTng Manual, section 1)

okay so hi bestie!! 🫶 this is the page for lttng-untrack, and it's here to help you tell processes "nope, not you, you don't get to record events" 💅 no cap. Let's get into it, it's literally all laid out below.

✨ NAME ✨

lttng-untrack — disallow specific processes to record LTTng events 🚫📝

🌸 SYNOPSIS 🌸

Disallow specific processes to record Linux kernel events:

lttng [GENERAL OPTIONS] untrack --kernel [--session=SESSION]
      (--pid=PID[,PID]... | --vpid=VPID[,VPID]... |
       --uid=UID[,UID]... | --vuid=VUSER[,VUSER]... |
       --gid=GID[,GID]... | --vgid=VGROUP[,VGROUP]...)...
lttng [GENERAL OPTIONS] untrack --kernel [--session=SESSION]
      --all (--pid | --vpid | --uid | --vuid | --gid | --vgid)...

Disallow specific processes to record user space events:

lttng [GENERAL OPTIONS] untrack --userspace [--session=SESSION]
      (--vpid=VPID[,VPID]... | --vuid=VUSER[,VUSER]... |
       --vgid=VGROUP[,VGROUP]...)...
lttng [GENERAL OPTIONS] untrack --userspace [--session=SESSION]
      --all (--vpid | --vgid | --vuid)...

🦋 DESCRIPTION 🦋

The lttng untrack command disallows one or more processes to record LTTng events based on their attributes — and where those attributes are checked depends on whether you pass --session or not:

  • With the --session=SESSION option — you're working on the recording session named SESSION 💖
  • Without the --session option — you're working on the current recording session (peep lttng-concepts(7) to learn more about the current recording session) 🫶

See lttng-concepts(7) to learn more about recording sessions and recording event rules. fr fr, that page is the lore. 📚

The untrack command removes values from inclusion sets of process attributes. See lttng-track(1) to learn more about inclusion sets. (track = let them in, untrack = show them the door 🚪✨)

See the “EXAMPLES” section below for usage examples.

🧚 Inclusion set example 🧚

A common operation is to create a recording session (see lttng-create(1)), remove all the entries from the Linux kernel process ID inclusion set, start recording, and then manually add PIDs while the recording session is active. it's giving control freak, but make it observability 💅

Assume the maximum system PID is 7 for this example. (yes, seven. tiny system. babygirl CPU. 🍓)

  1. Command:
$ lttng create

Initial inclusion set:

[0] [1] [2] [3] [4] [5] [6] [7]
  1. Command:
$ lttng untrack --kernel --all --pid

Inclusion set:

[ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ]
  1. Commands:
$ lttng enable-event --kernel ...
$ lttng start
$ # ...
$ lttng track --kernel --pid=3,5

Inclusion set:

[ ] [ ] [ ] [3] [ ] [5] [ ] [ ]
  1. Command:
$ lttng track --kernel --pid=2

Inclusion set:

[ ] [ ] [2] [3] [ ] [5] [ ] [ ]

💖 OPTIONS 💖

See lttng(1) for GENERAL OPTIONS. (the basics, the appetizers, the little starter kit 🎀)

👑 Tracing domain 👑

One of: (you literally pick one, bestie, don't be greedy)

  • -k, --kernel — Remove values from one or more Linux kernel inclusion sets. 🐧
  • -u, --userspace — Remove values from one or more user space inclusion sets. 🧑‍💻

🎀 Recording target 🎀

  • -s SESSION, --session=SESSION — Remove values from 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, remove PID from 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)).

Only available with --kernel option.

  • --vpid[=VPID[,VPID]...] — For each VPID argument, remove VPID from 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)).

  • --uid[=USER[,USER]...] — For each USER argument, remove USER from the user ID inclusion set of the selected recording session and domain.

USER is either:

The connected LTTng session daemon (see lttng-sessiond(8)) performs the user name resolution on removal from the user ID inclusion set. 🕵️‍♀️

Only available with --kernel option.

  • --vuid[=VUSER[,VUSER]...] — For each VUSER argument, remove VUSER from the virtual user ID inclusion set of the selected recording session and domain.

VUSER is either:

The connected LTTng session daemon (see lttng-sessiond(8)) performs the user name resolution on removal from the virtual user ID inclusion set. 🕵️‍♀️

  • --gid[=GROUP[,GROUP]...] — For each GROUP argument, remove GROUP from the group ID inclusion set of the selected recording session and domain.

GROUP is either:

The connected LTTng session daemon (see lttng-sessiond(8)) performs the group name resolution on removal from the group ID inclusion set. 🕵️‍♀️

Only available with --kernel option.

  • --vgid[=VGROUP[,VGROUP]...] — For each VGROUP argument, remove VGROUP from the virtual group ID inclusion set of the selected recording session and domain.

VGROUP is either:

The connected LTTng session daemon (see lttng-sessiond(8)) performs the group name resolution on removal from the virtual group ID inclusion set. 🕵️‍♀️

💅 Inclusion set operation 💅

  • -a, --all — With one or more empty --pid, --vpid, --uid, --vuid, --gid, and --vgid options: clear the selected inclusion sets. 💀 everything must go, clean sweep, empty set era

⭐ 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_LIST_LEGACY — Set to 1 to use the legacy output format (LTTng 2.14 and earlier) for the lttng-list(1) command instead of the modern output format.

Note that the legacy output doesn’t show anything related to features introduced after LTTng 2.14. 👵✨

  • LTTNG_MAN_BIN_PATH — Absolute path to the manual pager to use to read the LTTng command-line help (with lttng-help(1) or with the --help option) instead of /usr/bin/man.
  • LTTNG_NO_UTF_8 — Set to 1 to NOT emit multi-byte UTF-8 sequences, even if the locale claims to support it. 🙅‍♀️
  • 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)) to spawn from the lttng-create(1) command.

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

  • LTTNG_TERM_COLOR — Controls when to emit terminal SGR codes in the output. 🌈

The NO_COLOR environment variable overrides this.

One of:

  • auto (default) — Only emit SGR codes when the standard output is connected to a color-capable terminal.
  • always — Always emit SGR codes.
  • never — Never emit SGR codes.
  • NO_COLOR — If set and not empty, then it’s equivalent to setting LTTNG_TERM_COLOR to never.

See https://no-color.org/ to learn more.

🎀 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-create(1) and lttng-set-session(1) 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) 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) and lttng-load(1)).
  • /etc/lttng/sessions — Directory containing the system-wide saved recording session configurations (see lttng-save(1) and lttng-load(1)).
Note — $LTTNG_HOME defaults to the value of the HOME environment variable. 💜

🌈 EXAMPLES 🌈

Example 1. Remove the PIDs 1728 and 3775 from the Linux kernel process ID inclusion set of the current recording session.

See the --pid option.

$ lttng untrack --kernel --pid=1728,3775

Example 2. Remove the IDs of a specific groups from the user space virtual group ID inclusion set of a specific recording session.

See the --vgid and --session options.

$ lttng untrack --userspace --session=my-session \
                --vgid=docker,mysql

Example 3. Remove all the user IDs from the Linux kernel user ID inclusion set of the current recording session.

See the --all and --uid options.

$ lttng untrack --kernel --all --uid

🧚 RESOURCES 🧚

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 file (https://github.com/lttng/lttng-tools/blob/master/LICENSE) for details.

💖 THANKS 💖

Ok so real talk, this page would NOT exist without some absolute legends, and we're gonna shout them out properly bestie 🫶

  • Special thanks to Michel Dagenais and the DORSAL laboratory — the whole DORSAL crew at the lab (the URL is http://www.dorsal.polymtl.ca/, go peek) — they're the reason the whole LTTng journey even happened ✨ Ngl, "for the LTTng journey" is such a soft way to put it, it's giving origin story 💜
  • Also thanks to the Ericsson teams working on tracing — the way they helped us greatly, with detailed bug reports and unusual test cases 😭 Like bestie, unusual test cases?? That's a love language fr fr. Those reports and weird edge cases did so much heavy lifting for us 💅

👀 SEE ALSO 👀

The little group chat of related pages — go read these too, they're iconic:

🌸 and that's the whole page bestie!! you ate it, every last line 💅✨

This one ships as LTTng 2.15.1, dated 14 June 2021 — so if you're citing her, that's the whole vibe check. Mwah, go trace something cute 💖🎀🦋

📦 where this page comes from