lttng-untrack - Man Page

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 within:

With the --session=SESSION option

The recording session named SESSION.

Without the --session option

The current recording session (see 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.

The untrack command removes values from inclusion sets of process attributes. See lttng-track(1) to learn more about inclusion sets.

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.

Assume the maximum system PID is 7 for this example.

  1. Command:

    $ lttng create

    Initial inclusion set:

    [0] [1] [2] [3] [4] [5] [6] [7]
  2. Command:

    $ lttng untrack --kernel --all --pid

    Inclusion set:

    [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ]
  3. Commands:

    $ lttng enable-event --kernel ...
    $ lttng start
    $ # ...
    $ lttng track --kernel --pid=3,5

    Inclusion set:

    [ ] [ ] [ ] [3] [ ] [5] [ ] [ ]
  4. Command:

    $ lttng track --kernel --pid=2

    Inclusion set:

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

Options

See lttng(1) for GENERAL OPTIONS.

Tracing domain

One of:

-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 real user ID (see getuid(3)) of a process as seen from the root user namespace (see user_namespaces(7)).
  • A user name.

    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 real user ID (see getuid(3)) of a process as seen from the user namespace (see user_namespaces(7)).
  • A user name.

    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 real group ID (see getgid(3)) of a process as seen from the root user namespace (see user_namespaces(7)).
  • A group name.

    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 real group ID (see getgid(3)) of a process as seen from the user namespace (see user_namespaces(7)).
  • A group name.

    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.

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) 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)) to spawn from the lttng-create(1) 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-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)).

/usr/local/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

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-track(1), lttng-concepts(7)

Referenced By

lttng(1), lttng-concepts(7), lttng-create(1), lttng-enable-event(1), lttng-track(1).

14 June 2021 LTTng 2.13.0 LTTng Manual