The Linux Trace Toolkit: next generation <http://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
The LTTng relay daemon is responsible for receiving trace data from
possibly remote LTTng session/consumer daemons and for writing it to
the local file system. The relay daemon also accepts LTTng live
connections from compatible viewers; this is the official approach to
viewing LTTng events as they are emitted.
The relay daemon listens by default on all network interfaces to
gather trace data, but only on localhost for LTTng live connections.
The relay daemon does not require any particular permissions, as long
as it can write to the output directory and listen on the configured
ports. If a user is within a secured network and/or has proper
firewall settings, lttng-relayd can listen to LTTng live connections
from all network interfaces by specifying --live-port=tcp://localhost:5344.
Once a trace has been streamed completely, the trace can be processed
by any tool that can process an LTTng trace located on the local file
By default, the relay daemon writes the traces to:
Full session name.
You can override the default output directory prefix
($LTTNG_HOME/lttng-traces) with the --output option. The other parts
depend on the remote configuration.
The --control-port, --data-port, and --live-port options specify
The format of those URLs is:
tcp://(HOST | IPADDR):PORT
(HOST | IPADDR)
Binding hostname or IP address (IPv6 address must be enclosed in
brackets ([ and ]); see RFC 2732
Start as Unix daemon, but keep file descriptors (console) open.
Use the --daemonize option instead to close the file descriptors.
Start as Unix daemon, and close file descriptors (console). Use
the --background option instead to keep the file descriptors
-g GROUP, --group=GROUP
Use GROUP as Unix tracing group (default: tracing).
-o PATH, --output=PATH
Set base directory of written trace data to PATH.
See the Output directory section above for more information.
Three levels of verbosity are available, which are triggered by
appending additional v letters to the option (that is, -vv and
See the URL format section above for more information about the
syntax of the following options' URL argument.
-C URL, --control-port=URL
Listen to control data on URL URL (default: tcp://0.0.0.0:5342).
-D URL, --data-port=URL
Listen to trace data on URL URL (default: tcp://0.0.0.0:5343).
-L URL, --live-port=URL
Listen to LTTng live connections on URL URL (default:
Program information-h, --help
Set to 1 to abort the process after the first error is
Socket connection, receive and send timeout (milliseconds). A
value of 0 or -1 uses the timeout of the operating system
Path to relay daemon health’s socket.
User LTTng runtime and configuration directory.
Default output directory of LTTng traces. This can be overridden
with the --output option.
Note$LTTNG_HOME defaults to $HOME when not explicitly set.
As of this version, only the TCP protocol is supported for both
control and data ports. In future versions, TCP will remain the sole
available protocol for control data since those communications are
low-volume and need absolute reliability; trace data could be carried
For an unprivileged user running lttng-relayd, the maximum number of
file descriptors per process is usually 1024. This limits the number
of connections and opened trace files. This limit can be configured
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.
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
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 firstname.lastname@example.org. This page was obtained
from the project's upstream Git repository
⟨git://git.lttng.org/lttng-tools.git⟩ on 2017-03-13. 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
LTTng 2.10.0-pre 03/13/2017 LTTNG-RELAYD(8)