|
HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | ENVIRONMENT | FILES | RESOURCES | COPYRIGHT | THANKS | SEE ALSO | COLOPHON |
|
|
|
LTTNG-RELAYD(8) LTTng Manual LTTNG-RELAYD(8)
lttng-relayd - LTTng relay daemon
lttng-relayd [--background | --daemonize] [--config=PATH]
[--control-port=URL] [--data-port=URL] [--fd-pool-size=COUNT]
[--live-port=URL] [--dynamic-port-allocation] [--output=DIR]
[--group=GROUP] [--verbose]... [--working-directory=DIR]
[--group-output-by-host | --group-output-by-session] [--disallow-clear]
[--pid-file=PATH] [--sig-parent]
The Linux Trace Toolkit: next generation <https://lttng.org/> is
an open-source software package used for correlated tracing of the
Linux kernel, user applications, and user libraries.
LTTng consists of Linux kernel modules (for Linux kernel tracing)
and dynamically loaded libraries (for user application and library
tracing).
An LTTng relay daemon, lttng-relayd, is a program which receives
trace data from (possibly remote) LTTng session/consumer daemons
and which writes it to the local file system. The relay daemon
also accepts LTTng live connections from compatible readers (for
example, babeltrace2(1)); this is the recommended approach to read
trace data while the remote recording session is active.
By default, a relay daemon listens on all network interfaces to
receive trace data, but only on localhost for LTTng live
connections. Override the listening URLs with the --control-port,
--data-port, and --live-port options (see the “URL format” section
below). For example, use the --live-port=tcp://0.0.0.0:5344 option
to make a relay daemon listen to LTTng live connections on all
network interfaces.
Once LTTng has completely sent a trace to a relay daemon RD, any
LTTng trace reader can read the trace located on the local file
system of RD.
By default, lttng-relayd doesn’t start as a daemon. Make it a
daemon with the --daemonize or --background option. With those
options, lttng-relayd ensures the daemon is listening to incoming
connections before it exits. Make lttng-relayd write its process
ID to a file with the --pid-file option.
Daemon configuration
When you run lttng-relayd, it configures itself from, in this
order:
1. The INI configuration file /usr/local/etc/lttng/lttng.conf, if
any.
2. The INI configuration file $LTTNG_HOME/.lttng/lttng.conf, if
any.
$LTTNG_HOME defaults to $HOME.
3. With the --config=PATH option: the INI configuration file
PATH.
4. The command-line options.
Each step can override a previous configuration property.
In INI configuration files, the session daemon only reads the
properties under the relayd INI section. Each INI property is:
Key
The long name of a command-line option to set (see the
“OPTIONS” section below).
Value
The selected command-line option accepts an argument
Option argument (string).
The selected command-line option is a switch
true, yes, on
Enable the option.
false, no, off
Disable the option.
INI configuration file example:
[relayd]
daemonize=yes
live-port=tcp://0.0.0.0:4567
disallow-clear=yes
Output directory
The relay daemon uses different output path patterns depending on:
• Its configuration.
See the “Daemon configuration” section above.
• The recording session configuration of the connected peer.
• The LTTng session daemon (see lttng-sessiond(8)) version of
the connected peer.
Consider the following variables:
BASE
Base output directory: $LTTNG_HOME/lttng-traces ($LTTNG_HOME
defaults to $HOME) or the argument of the --output option.
HOSTNAME
Hostname of the connected peer.
SESSION
Recording session name.
DATETIME
Unique recording session date/time.
TRACEDIR
Custom trace directory path (TRACEDIR part of the argument of
the --set-url option of the lttng-create(1) command, if any).
SESSIONDV
The version of the LTTng session daemon of the connected peer.
The relay daemon output path patterns are:
With the --group-output-by-host option (hostname grouping)
Without a custom trace directory
BASE/HOSTNAME/SESSION-DATETIME
With a custom trace directory
BASE/HOSTNAME/TRACEDIR
With the --group-output-by-session option (recording session
grouping)
Without a custom trace directory
SESSIONDV is at least 2.4
BASE/SESSION/HOSTNAME-DATETIME
Otherwise
Defaults to the hostname grouping pattern:
BASE/HOSTNAME/SESSION-DATETIME
With a custom trace directory
SESSIONDV is at least 2.4
BASE/SESSION/HOSTNAME-DATETIME/TRACEDIR
Otherwise
Defaults to the hostname grouping pattern:
BASE/HOSTNAME/TRACEDIR
URL format
The argument of the --control-port=URL, --data-port=URL, and
--live-port=URL options is an URL.
The format of URL is:
tcp://(HOST | IPADDR):PORT
with:
(HOST | IPADDR)
Binding hostname or IP address.
IPv6 address must be enclosed in square brackets ([ and ]);
see RFC 2732 <https://www.ietf.org/rfc/rfc2732.txt>.
PORT
TCP port.
If this value is 0 and the --dynamic-port-allocation option is
set, then the operating system assigns a port number itself.
General daemon configuration
-b, --background
Start as a Unix daemon, but keep file descriptors (console)
open.
With this option, lttng-relayd ensures the daemon is listening
to incoming connections before it exits.
Use the --daemonize option instead to close the file
descriptors.
-f PATH, --config=PATH
Configure the daemon using the INI configuration file PATH in
addition to the default configuration files and the
command-line options.
See the “Daemon configuration” section above.
-d, --daemonize
Start as a Unix daemon and close file descriptors (console).
With this option, lttng-relayd ensures the daemon is listening
to incoming connections before it exits.
Use the --background option instead to keep the file
descriptors open.
-x, --disallow-clear
Disallow clearing operations (see lttng-clear(1)).
See also the LTTNG_RELAYD_DISALLOW_CLEAR environment variable.
--dynamic-port-allocation
Let the operating system assign the control, data, and live
ports if their respective option is missing (--control-port,
--data-port, and --live-port) or if their port number part
is 0.
With this option, lttng-relayd writes the control.port,
data.port, and live.port files, as needed, to its runtime and
configuration directory ($LTTNG_HOME/.lttng). Such a port file
contains the textual port number (decimal) followed with a
newline.
--fd-pool-size=SIZE
Set the size of the file descriptor pool to SIZE file
descriptors.
SIZE is the maximum number of file descriptors that the relay
daemon may keep open simultaneously.
Default: the soft RLIMIT_NOFILE resource limit of the process
(see getrlimit(2)).
-g GROUP, --group=GROUP
Set the Unix tracing group to GROUP instead of tracing.
This option is only meaningful when the root Unix user starts
lttng-relayd.
Members of the Unix tracing group may connect to the health
check socket of the relay daemon.
See also the LTTNG_RELAYD_HEALTH environment variable.
-P PATH, --pid-file=PATH
Write the process ID (PID) of the lttng-relayd process to
PATH.
Such a file contains the textual PID (decimal) followed with a
newline.
lttng-relayd doesn’t use this file and removes it when it
exits.
-S, --sig-parent
Send the USR1 signal to the parent process to notify
readiness.
You can also use the --daemonize or --background option, in
which case lttng-relayd ensures the daemon is ready to receive
client commands before it exits.
-v, --verbose
Increase verbosity.
Specify this option up to three times to get more levels of
verbosity.
-w DIR, --working-directory=DIR
Set the working directory of the processes the relay daemon
creates to DIR.
See also the LTTNG_RELAYD_WORKING_DIRECTORY environment
variable.
Output
See the “Output directory” section above to learn more.
-p, --group-output-by-host
Group the written trace directories by hostname.
As of LTTng 2.15.1, this is the default output grouping
strategy, but this may change in the future.
-s, --group-output-by-session
Group the written trace directories by recording session name
instead of by hostname.
-o DIR, --output=DIR
Set the base output directory of the written trace directories
to DIR.
Ports
See the “URL format” section above to learn more about the syntax
of the URL argument of the following options.
For the following options: if the --dynamic-port-allocation option
is set and the port option is either missing or the port number
part of URL is 0, then the operating system assigns a port number
itself.
-C URL, --control-port=URL
Listen to control data on URL URL.
Default: tcp://0.0.0.0:5342.
-D URL, --data-port=URL
Listen to trace data on URL URL.
Default: tcp://0.0.0.0:5343.
-L URL, --live-port=URL
Listen to LTTng live connections on URL URL.
Default: tcp://localhost:5344.
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.
-V, --version
Show version and quit.
0
Success
1
Error
3
Fatal error
LTTNG_ABORT_ON_ERROR
Set to 1 to abort the process after the first error is
encountered.
LTTNG_NETWORK_SOCKET_TIMEOUT
Socket connection, receive, and send timeout (milliseconds).
Set to 0 or -1 to set an infinite timeout (default).
LTTNG_RELAYD_DISALLOW_CLEAR
Set to 1 to disallow clearing operations (see lttng-clear(1)).
The --disallow-clear option overrides this environment
variable.
LTTNG_RELAYD_HEALTH
Path to the health check socket of the relay daemon.
LTTNG_RELAYD_TCP_KEEP_ALIVE
Set to 1 to enable TCP keep-alive.
The TCP keep-alive mechanism allows the detection of dead
peers (lttng-sessiond(8)) in cases of unclean termination (for
example, a hard reset) of a peer.
Supported on Linux and Solaris only. The default behaviour of
the TCP keep-alive mechanism is OS-specific.
Search for tcp_keepalive in tcp(7) to learn more.
LTTNG_RELAYD_TCP_KEEP_ALIVE_ABORT_THRESHOLD
The time threshold (seconds) to abort a TCP connection after
the keep-alive probing mechanism has failed.
Set to 0 or -1 to use the value chosen by the operating system
(default).
Supported on Solaris 11 only.
Search for tcp_keepalive_abort_threshold in tcp(7) to learn
more.
LTTNG_RELAYD_TCP_KEEP_ALIVE_IDLE_TIME
Number of seconds a connection needs to be idle before TCP
begins sending out keep-alive probes.
Set to 0 or -1 to use the value chosen by the operating system
(default).
Supported on Linux and Solaris 11 only.
On Solaris 11, the accepted values are -1, 0, and 10 to
864000.
Search for tcp_keepalive_time and tcp_keepalive_interval in
tcp(7) on Solaris 11 to learn more.
LTTNG_RELAYD_TCP_KEEP_ALIVE_MAX_PROBE_COUNT
Maximum number of TCP keep-alive probes to send before giving
up and killing the connection if no response is obtained from
the other end.
Set to 0 or -1 to use the value chosen by the operating system
(default).
Supported on Linux only.
Search for tcp_keepalive_probes in tcp(7) to learn more.
LTTNG_RELAYD_TCP_KEEP_ALIVE_PROBE_INTERVAL
Number of seconds between TCP keep-alive probes.
Set to 0 or -1 to use the value chosen by the operating system
(default).
Supported on Linux only.
Search for tcp_keepalive_intvl in tcp(7) to learn more.
LTTNG_RELAYD_WORKING_DIRECTORY
Working directory of the processes the relay daemon creates.
The --working-directory option overrides this environment
variable.
$LTTNG_HOME/.lttng
Unix user’s LTTng runtime and configuration directory.
$LTTNG_HOME/lttng-traces
Default base output directory of LTTng traces.
Override this path with the --output option.
Note
$LTTNG_HOME defaults to $HOME.
• 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
• Mastodon <https://mastodon.social/@lttng>
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.
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.
babeltrace2(1), lttng(1), lttng-sessiond(8)
This page is part of the LTTng-Tools (LTTng tools) project.
Information about the project can be found at ⟨http://lttng.org/⟩.
It is not known how to report bugs for this man page; if you know,
please send a mail to man-pages@man7.org. This page was obtained
from the project's upstream Git repository
⟨https://github.com/lttng/lttng-tools.git⟩ on 2026-08-04. (At
that time, the date of the most recent commit that was found in
the repository was 2026-07-30.) 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
man-pages@man7.org
LTTng 2.15.1 1 April 2025 LTTNG-RELAYD(8)
Pages that refer to this page: lttng(1), lttng-clear(1), lttng-create(1), lttng-destroy(1), lttng-rotate(1), lttng-snapshot(1), babeltrace2-source.ctf.lttng-live(7), lttng-concepts(7)
|
HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|