Clarify kernel version check error messages

[lttng-tools.git] / doc / man / lttng-sessiond.8

.TH "LTTNG-SESSIOND" "8" "January 31, 2012" "" ""

.SH "NAME"
lttng-sessiond \- LTTng 2.x central tracing registry session daemon.

.SH "SYNOPSIS"

.PP
.nf
lttng-sessiond [OPTIONS]
.fi
.SH "DESCRIPTION"

.PP
The LTTng project aims at providing highly efficient tracing tools for Linux.
It's tracers help tracking down performance issues and debugging problems
involving multiple concurrent processes and threads. Tracing across multiple
systems is also possible.

The session daemon, acting as a tracing registry, allow you to interact with
multiple tracers (kernel and user-space) inside the same container, a tracing
session. Trace can be gathered from the kernel and/or instrumented applications
(lttng-ust(3)). Aggregating those traces is done using a viewer, like the
babeltrace(1) text viewer.

In order to trace the kernel, the session daemon needs to be running as root.
LTTng provides the use of a \fBtracing group\fP (default: tracing). Whomever is
in that group can interact with the root session daemon and thus trace the
kernel. Session daemons can co-exist meaning that you can have a session daemon
running as Alice that can be used to trace her applications along side with a
root daemon or even a Bob daemon. We highly recommend to start the session
daemon at boot time for stable and long term tracing.

The session daemon is in charge of managing trace data consumers by spawning
them when the time has come. The user don't need to manage the lttng-consumerd.
.SH "OPTIONS"

.PP
This program follows the usual GNU command line syntax with long options starting
with two dashes. Below is a summary of the available options.
.PP

.TP
.BR "-h, --help"
Show summary of possible options and commands
.TP
.BR "\-V, \-\-version"
Show version.
.TP
.BR "-v, --verbose"
Increase verbosity

There is three debugging level which will print on stderr. Maximum verbosity is
\fB-vvv\fP.
.TP
.BR "    --verbose-consumer"
Verbose mode for consumer. Activate DBG() macro.
.TP
.BR "-d, --daemonize"
Start as a daemon
.TP
.BR "-b, --background"
Start as a daemon, keeping console open
.TP
.BR "-g, --group=NAME"
Specify the tracing group name. (default: tracing)
.TP
.BR "-V, --version"
Show version number
.TP
.BR "-S, --sig-parent"
Send SIGUSR1 to parent pid to notify readiness.

This is used by \fBlttng(1)\fP to get notified when the session daemon is ready
to accept command. When building a third party tool over liblttng-ctl, this option
can be very handy to synchronize the control tool and the session daemon.
.TP
.BR "-q, --quiet"
No output at all.
.TP
.BR "    --no-kernel"
No kernel tracer support
.TP
.BR "    --agent-tcp-port"
Agent application registration TCP port (default: 5345)
.TP
.BR "    --kmod-probes=probe1, probe2, ..."
Specify the kernel modules containing LTTng probes to load by the session daemon.
Only the component name of the probe needs to be specified, e.g. to load the
lttng-probe-irq and lttng-probe-sched use: --kmod-probes="irq, sched".
.TP
.BR "    --extra-kmod-probes=probe1, probe2, ..."
Specify extra kernel modules containing LTTng probes to be loaded by the session
daemon. The list follows the format of the \fB--kmod-probes\fP option.
This list is appended to the list provided by \fB--kmod-probes\fP or, if
\fB--kmod-probes\fP is missing, to the default list of probes.
.TP
.BR "-c, --client-sock=PATH"
Specify path for the client unix socket
.TP
.BR "-a, --apps-sock PATH"
Specify path for apps unix socket
.TP
.BR "    --kconsumerd-err-sock=PATH"
Specify path for the kernel consumer error socket
.TP
.BR "    --kconsumerd-cmd-sock=PATH
Specify path for the kernel consumer command socket
.TP
.BR "    --ustconsumerd32-err-sock=PATH
Specify path for the 32-bit UST consumer error socket
.TP
.BR "    --ustconsumerd64-err-sock=PATH
Specify path for the 64-bit UST consumer error socket
.TP
.BR "    --ustconsumerd32-cmd-sock=PATH
Specify path for the 32-bit UST consumer command socket
.TP
.BR "    --ustconsumerd64-cmd-sock=PATH
Specify path for the 64-bit UST consumer command socket
.TP
.BR "    --consumerd32-path=PATH
Specify path for the 32-bit UST consumer daemon binary
.TP
.BR "    --consumerd32-libdir=PATH
Specify path for the 32-bit UST consumer daemon libraries
.TP
.BR "    --consumerd64-path=PATH
Specify path for the 64-bit UST consumer daemon binary
.TP
.BR "    --consumerd64-libdir=PATH
Specify path for the 64-bit UST consumer daemon libraries
.TP
.BR "-l, --load PATH
Specify path from which to automatically load session configuration(s).
.TP
.BR "-f, --config PATH
Specify path from which to load daemon configuration.

.SH "LOADING SESSIONS"

.PP
By default, the session daemon tries to load session configuration(s) located
in the user default directory \fB~/.lttng/sessions/auto/\fP and in the system
wide one in \fB/etc/lttng/sessions/auto/\fP. Note that the directory containing
the session's configuration and lttng-sessiond MUST have the same UID for them
to be automatically loaded.

Specifying a path with \-l, \-\-load PATH overrides the default directory and
UID check. The lttng-sessiond will simply check if it's accessible and try to
load every session file in it.
.PP

.SH "ENVIRONMENT VARIABLES"

.PP
Note that all command line options will override environment variables.
.PP

.PP
.IP "LTTNG_CONSUMERD32_BIN"
Specify the 32-bit consumer binary path. \fB--consumerd32-path\fP
override this variable.
.IP "LTTNG_CONSUMERD64_BIN"
Specify the 64-bit consumer binary path. \fB--consumerd64-path\fP
override this variable.
.IP "LTTNG_CONSUMERD32_LIBDIR"
Specify the 64-bit library path containing libconsumer.so.
\fB--consumerd32-libdir\fP override this variable.
.IP "LTTNG_CONSUMERD64_LIBDIR"
Specify the 32-bit library path containing libconsumer.so.
\fB--consumerd64-libdir\fP override this variable.
.IP "LTTNG_DEBUG_NOCLONE"
Debug-mode disabling use of clone/fork. Insecure, but required to allow
debuggers to work with sessiond on some operating systems.
.IP "LTTNG_APP_SOCKET_TIMEOUT"
Control the timeout of application's socket when sending and receiving
commands. Takes an integer parameter: the timeout value, in seconds.
After this period of time, the application is unregistered by the
session daemon. A value of 0 or -1 means an infinite timeout. Default
value is 5 seconds.
.IP "LTTNG_NETWORK_SOCKET_TIMEOUT"
Control timeout of socket connection, receive and send. Takes an integer
parameter: the timeout value, in milliseconds. A value of 0 or -1 uses
the timeout of the operating system (this is the default).
.IP "LTTNG_SESSION_CONFIG_XSD_PATH"
Specify the path that contains the XML session configuration schema (xsd).
.IP "LTTNG_KMOD_PROBES"
Specify the kernel modules probes that should be loaded by the session daemon.
.IP "LTTNG_EXTRA_KMOD_PROBES"
Specify extra kernel modules probes that should be loaded by the session daemon.
.SH "SEE ALSO"

.PP
babeltrace(1), lttng-ust(3), lttng(1)
.PP

.SH "LIMITATIONS"

.PP
For unprivileged user running lttng-sessiond, the maximum number of file
descriptors per process is usually 1024. This limits the number of traceable
applications since for each instrumented application there is two file
descriptors per-CPU and one more socket for bidirectional communication.

For the root user, the limit is bumped to 65535. Future version will deal with
this limitation.
.PP

.SH "BUGS"

.PP
No show stopper bugs are known yet in this version.

If you encounter any issues or usability problem, please report it on our
mailing list <lttng-dev@lists.lttng.org> to help improve this project.
.SH "CREDITS"

.PP
lttng-sessiond is distributed under the GNU General Public License version 2. See the
file COPYING for details.
.PP
A Web site is available at http://lttng.org for more information on the LTTng
project.
.PP
You can also find our git tree at http://git.lttng.org.
.PP
Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
.PP
You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
.PP
.SH "THANKS"

.PP
Thanks to Yannick Brosseau without whom this project would never have been so
lean and mean! Also thanks to the Ericsson teams working on tracing which helped
us greatly with detailed bug reports and unusual test cases.

Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
maintainer) and Jon Bernard for our Debian packages.

Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
Montreal for the LTTng journey.
.PP
.SH "AUTHORS"

.PP
lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
David Goulet. More people have since contributed to it. It is currently
maintained by Jérémie Galarneau <jeremie.galarneau@efficios.com>.
.PP