lttng-add-context(1) — Linux manual page


LTTNG-ADD-CONTEXT(1)            LTTng Manual            LTTNG-ADD-CONTEXT(1)

NAME         top

       lttng-add-context - Add context fields to an LTTng channel

SYNOPSIS         top

       Add context fields to a channel:

       lttng [GENERAL OPTIONS] add-context
             (--kernel | --userspace | --jul | --log4j)
             [--session=SESSION] [--channel=CHANNEL]
             --type=TYPE [--type=TYPE]...

       List the available context fields:

       lttng [GENERAL OPTIONS] add-context --list

DESCRIPTION         top

       The lttng add-context command adds one or more context fields to a

       Channels are created with the lttng-enable-channel(1) command.

       When context fields are added to a channel, all the events emitted
       within this channel contain the dynamic values of those context

       If the --session option is omitted, the current tracing session is
       used. If the --channel option is omitted, the context fields are
       added to all the selected tracing session’s channels.

       Many context fields can be added to a channel at once by repeating
       the --type option.

       perf counters are available as per-CPU (perf:cpu: prefix) as well as
       per-thread (perf:thread: prefix) counters. Currently, per-CPU
       counters can only be used in the Linux kernel tracing domain, while
       per-thread counters can only be used in the user space tracing

       It is also possible to enable PMU counters by raw ID using the
       perf:cpu:raw:rN:NAME (Linux kernel tracing domain) or
       perf:thread:raw:rN:NAME (user space tracing domain), with:

           A hexadecimal event descriptor which is the same format as used
           by perf-record(1): a concatenation of the event number and umask
           value provided by the processor’s manufacturer. The possible
           values for this field are processor-specific.

           Custom name to easily recognize the counter.

       Application-specific context fields can be added to a channel using
       the following syntax:



           Provider name.

           Context type name.

           Make sure to single-quote the type when running the command from
           a shell, as $ is a special character for variable substitution in
           most shells.

       Use the --list option without other arguments to list the available
       context field names.

       See the LIMITATIONS section below for a list of limitations to

OPTIONS         top

       General options are described in lttng(1).

       One of:

       -j, --jul
           Add context to channel in the java.util.logging (JUL) domain.

       -k, --kernel
           Add context to channel in the Linux kernel domain.

       -l, --log4j
           Add context to channel in the Apache log4j domain.

       -u, --userspace
           Add context to channel in the user space domain.

       -c CHANNEL, --channel=CHANNEL
           Add context fields to a channel named CHANNEL instead of adding
           them to all the channels.

       -s SESSION, --session=SESSION
           Add context fields to a channel in the tracing session named
           SESSION instead of the current tracing session.

           List the available context fields. Use this option alone.

       -t TYPE, --type=TYPE
           Add context field named TYPE. This option can be repeated as many
           times as needed on the command-line.

   Program information
       -h, --help
           Show command help.

           This option, like lttng-help(1), attempts to launch /usr/bin/man
           to view the command’s man page. The path to the man pager can be
           overridden by the LTTNG_MAN_BIN_PATH environment variable.

           List available command options.

LIMITATIONS         top

       As of this version of LTTng, it is not possible to add context fields
       to a channel once its tracing session has been started (see
       lttng-start(1)) at least once.


           Set to 1 to abort the process after the first error is

           Overrides the $HOME environment variable. Useful when the user
           running the commands has a non-writable home directory.

           Absolute path to the man pager to use for viewing help
           information about LTTng commands (using lttng-help(1) or lttng
           COMMAND --help).

           Path in which the session.xsd session configuration XML schema
           may be found.

           Full session daemon binary path.

           The --sessiond-path option has precedence over this environment

       Note that the lttng-create(1) command can spawn an LTTng session
       daemon automatically if none is running. See lttng-sessiond(8) for
       the environment variables influencing the execution of the session

FILES         top

           User LTTng runtime configuration.

           This is where the per-user current tracing session is stored
           between executions of lttng(1). The current tracing session can
           be set with lttng-set-session(1). See lttng-create(1) for more
           information about tracing sessions.

           Default output directory of LTTng traces. This can be overridden
           with the --output option of the lttng-create(1) command.

           User LTTng runtime and configuration directory.

           Default location of saved user tracing sessions (see
           lttng-save(1) and lttng-load(1)).

           System-wide location of saved tracing sessions (see lttng-save(1)
           and lttng-load(1)).

           $LTTNG_HOME defaults to $HOME when not explicitly set.

EXIT STATUS         top


           Command error

           Undefined command

           Fatal error

           Command warning (something went wrong during the command)

BUGS         top

       If you encounter any issue or usability problem, please report it on
       the LTTng bug tracker <>.

RESOURCES         top

       ·   LTTng project website <>

       ·   LTTng documentation <>

       ·   Git repositories <>

       ·   GitHub organization <>

       ·   Continuous integration <>

       ·   Mailing list <> for support and

       ·   IRC channel <irc://>: #lttng on

COPYRIGHTS         top

       This program is part of the LTTng-tools project.

       LTTng-tools is distributed under the GNU General Public License
       version 2 <>.
       See the LICENSE <
       tools/blob/master/LICENSE> file for details.

THANKS         top

       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.

AUTHORS         top

       LTTng-tools was originally written by Mathieu Desnoyers, Julien
       Desfossez, and David Goulet. More people have since contributed to

       LTTng-tools is currently maintained by Jérémie Galarneau

SEE ALSO         top


COLOPHON         top

       This page is part of the LTTng-Tools (    LTTng tools) project.
       Information about the project can be found at ⟨⟩.
       It is not known how to report bugs for this man page; if you know,
       please send a mail to  This page was obtained
       from the project's upstream Git repository
       ⟨git://⟩ on 2019-11-19.  (At that time,
       the date of the most recent commit that was found in the repository
       was 2019-11-14.)  If you discover any rendering problems in this HTML
       version of the page, or you believe there is a better or more up-to-
       date source for the page, or you have corrections or improvements to
       the information in this COLOPHON (which is not part of the original
       manual page), send a mail to

LTTng 2.12.0-pre                 10/29/2018             LTTNG-ADD-CONTEXT(1)

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