7 lttng-sessiond - LTTng 2 tracing session daemon
13 *lttng-sessiond* [option:--background | option:--daemonize] [option:--sig-parent]
14 [option:--config='PATH'] [option:--group='GROUP'] [option:--load='PATH']
15 [option:--agent-tcp-port='PORT']
16 [option:--apps-sock='PATH'] [option:--client-sock='PATH']
17 [option:--no-kernel | [option:--kmod-probes='PROBE'[,'PROBE']...]
18 [option:--extra-kmod-probes='PROBE'[,'PROBE']...]
19 [option:--kconsumerd-err-sock='PATH']
20 [option:--kconsumerd-cmd-sock='PATH']]
21 [option:--ustconsumerd32-err-sock='PATH']
22 [option:--ustconsumerd64-err-sock='PATH']
23 [option:--ustconsumerd32-cmd-sock='PATH']
24 [option:--ustconsumerd64-cmd-sock='PATH']
25 [option:--consumerd32-path='PATH'] [option:--consumerd32-libdir='PATH']
26 [option:--consumerd64-path='PATH'] [option:--consumerd64-libdir='PATH']
27 [option:--quiet | [option:-v | option:-vv | option:-vvv] [option:--verbose-consumer]]
32 The http://lttng.org/[_Linux Trace Toolkit: next generation_] is an open
33 source software package used for correlated tracing of the Linux kernel,
34 user applications, and user libraries.
36 LTTng consists of Linux kernel modules (for Linux kernel tracing) and
37 dynamically loaded libraries (for user application and library tracing).
39 The _LTTng session daemon_ is a tracing registry which allows the user
40 to interact with multiple tracers (kernel and user space) within the
41 same container, a _tracing session_. Traces can be gathered from the
42 Linux kernel and/or from instrumented applications (see
43 man:lttng-ust(3)). You can aggregate and read the events of LTTng
44 traces using man:babeltrace(1).
46 To trace the Linux kernel, the session daemon needs to be running as
47 `root`. LTTng uses a _tracing group_ to allow specific users to interact
48 with the root session daemon. The default tracing group name is
49 `tracing`. You can use the option:--group option to set the tracing
52 Session daemons can coexist. You can have a session daemon running as
53 user Alice that can be used to trace her applications alongside a root
54 session daemon or a session daemon running as user Bob.
56 The LTTng session daemon manages trace data consumer daemons by spawning
57 them when necessary. You do not need to manage the consumer daemons
60 NOTE: It is highly recommended to start the session daemon at boot time
61 for stable and long-term tracing.
64 Automatic loading of tracing session configurations
65 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
66 When the session daemon starts, it automatically loads session
69 The following directories are searched, non-recursively, in this order
70 for configuration files to load on launch:
72 . `$LTTNG_HOME/.lttng/sessions/auto` (`$LTTNG_HOME` defaults to `$HOME`)
73 . +{system_sessions_auto_dir}+
75 Note that both the directory containing the tracing session
76 configurations _and_ the session daemon binary _must_ share the same UID
77 for the configurations to be automatically loaded.
79 The option:--load option overrides the default directories _and_ the UID
80 check. The session daemon simply checks if the path is accessible and
81 tries to load every tracing session configuration in it. When this
82 option is specified, the default directories are :not: searched for
83 configuration files. When the option is not specified, _both_ default
84 directories are searched for configuration files.
86 If the option:--load option's argument is a directory, then all the
87 tracing session configurations found in all the files in this directory
88 are loaded. If the argument is a file, then all the tracing session
89 configurations found in this file are loaded.
96 option:-b, option:--background::
97 Start as Unix daemon, but keep file descriptors (console) open.
98 Use the option:--daemonize option instead to close the file
101 option:-d, option:--daemonize::
102 Start as Unix daemon, and close file descriptors (console). Use the
103 option:--background option instead to keep the file descriptors
106 option:-f, option:--config='PATH'::
107 Load session daemon configuration from path 'PATH'.
109 option:-g, option:--group='GROUP'::
110 Use 'GROUP' as Unix tracing group (default: `tracing`).
112 option:-l, option:--load='PATH'::
113 Automatically load tracing session configurations from 'PATH',
114 either a directory or a file, instead of loading them from the
115 default search directories.
117 option:-S, option:--sig-parent::
118 Send `SIGUSR1` to parent process to notify readiness.
120 NOTE: This is used by man:lttng(1) to get notified when the
121 session daemon is ready to accept commands. When building a third party
122 tool on liblttng-ctl, this option can be very handy to synchronize the
123 control tool and the session daemon.
128 option:--extra-kmod-probes='PROBE'[,'PROBE']...::
129 Load specific LTTng Linux kernel modules when kernel tracing
130 is enabled (option:--no-kernel option is :not: specified), in
131 addition to loading the default list of LTTng kernel modules.
133 Only the name of the probe needs to be specified, without the
134 `lttng-probe-` prefix and without the kernel module extension suffix.
135 For example, specify `sched` to load the `lttng-probe-sched.ko` kernel
138 option:--kmod-probes='PROBE'[,'PROBE']...::
139 Only load specific LTTng Linux kernel modules when kernel tracing
140 is enabled (option:--no-kernel option is :not: specified).
142 Only the name of the probe needs to be specified, without the
143 `lttng-probe-` prefix and without the kernel module extension suffix.
144 For example, specify `sched` to load the `lttng-probe-sched.ko` kernel
148 Disable Linux kernel tracing.
153 option:--agent-tcp-port='PORT'::
154 Listen on TCP port 'PORT' for agent application registrations
155 (default: {default_agent_tcp_port}).
157 option:-a 'PATH', option:--apps-sock='PATH'::
158 Set application Unix socket path to 'PATH'.
160 option:-c 'PATH', option:--client-sock='PATH'::
161 Set client Unix socket path to 'PATH'.
163 option:--consumerd32-libdir='PATH'::
164 Set 32-bit consumer daemon library directory to 'PATH'.
166 option:--consumerd32-path='PATH'::
167 Set 32-bit consumer daemon binary path to 'PATH'.
169 option:--consumerd64-libdir='PATH'::
170 Set 64-bit consumer daemon library directory to 'PATH'.
172 option:--consumerd64-path='PATH'::
173 Set 64-bit consumer daemon binary path to 'PATH'.
175 option:--kconsumerd-cmd-sock='PATH'::
176 Set Linux kernel consumer daemon's command Unix socket path
179 option:--kconsumerd-err-sock='PATH'::
180 Set Linux kernel consumer daemon's error Unix socket path
183 option:--ustconsumerd32-cmd-sock='PATH'::
184 Set 32-bit consumer daemon's command Unix socket path to 'PATH'.
186 option:--ustconsumerd64-cmd-sock='PATH'::
187 Set 64-bit consumer daemon's command Unix socket path to 'PATH'.
189 option:--ustconsumerd32-err-sock='PATH'::
190 Set 32-bit consumer daemon's error Unix socket path to 'PATH'.
192 option:--ustconsumerd64-err-sock='PATH'::
193 Set 64-bit consumer daemon's error Unix socket path to 'PATH'.
198 option:-q, option:--quiet::
199 Suppress all messages, including warnings and errors.
201 option:-v, option:--verbose::
204 Three levels of verbosity are available, which are triggered by
205 appending additional `v` letters to the option
206 (that is, `-vv` and `-vvv`).
208 option:--verbose-consumer::
209 Increase verbosity of consumer daemons spawned by this session
215 option:-h, option:--help::
218 option:-V, option:--version::
222 ENVIRONMENT VARIABLES
223 ---------------------
224 Note that command-line options override their equivalent environment
227 `LTTNG_ABORT_ON_ERROR`::
228 Set to 1 to abort the process after the first error is encountered.
230 `LTTNG_APP_SOCKET_TIMEOUT`::
231 Application socket's timeout (seconds) when sending/receiving
232 commands. After this period of time, the application is unregistered
233 by the session daemon. A value of 0 or -1 means an infinite timeout.
234 Default value: {default_app_socket_rw_timeout}.
236 `LTTNG_CONSUMERD32_BIN`::
237 32-bit consumer daemon binary path.
239 The option:--consumerd32-path option overrides this variable.
241 `LTTNG_CONSUMERD32_LIBDIR`::
242 32-bit consumer daemon library path.
244 The option:--consumerd32-libdir option overrides this variable.
246 `LTTNG_CONSUMERD64_BIN`::
247 64-bit consumer daemon binary path.
249 The option:--consumerd64-path option overrides this variable.
251 `LTTNG_CONSUMERD64_LIBDIR`::
252 64-bit consumer daemon library path.
254 The option:--consumerd64-libdir option overrides this variable.
256 `LTTNG_DEBUG_NOCLONE`::
257 Set to 1 to disable the use of `clone()`/`fork()`. Setting this
258 variable is considered insecure, but it is required to allow
259 debuggers to work with the session daemon on some operating systems.
261 `LTTNG_EXTRA_KMOD_PROBES`::
262 Load specific LTTng Linux kernel modules when kernel tracing
263 is enabled (option:--no-kernel option is :not: specified), in
264 addition to loading the default list of LTTng kernel modules.
266 The option:--extra-kmod-probes option overrides this variable.
268 `LTTNG_KMOD_PROBES`::
269 Only load specific LTTng Linux kernel modules when kernel tracing
270 is enabled (option:--no-kernel option is :not: specified).
272 The option:--kmod-probes option overrides this variable.
274 `LTTNG_NETWORK_SOCKET_TIMEOUT`::
275 Socket connection, receive and send timeout (milliseconds). A value
276 of 0 or -1 uses the timeout of the operating system (default).
278 `LTTNG_SESSION_CONFIG_XSD_PATH`::
279 Tracing session configuration XML schema definition (XSD) path.
284 `$LTTNG_HOME/.lttng`::
285 User LTTng runtime and configuration directory.
287 `$LTTNG_HOME/lttng-traces`::
288 Default output directory of LTTng traces. This can be overridden
289 with the nloption:--output option of the man:lttng-create(1)
292 `$LTTNG_HOME/.lttng/sessions/auto`::
293 Directory from which user tracing configuration files are
294 automatically loaded when the session daemon starts (see
295 man:lttng-save(1) and man:lttng-load(1) for saving
296 and loading tracing sessions).
298 +{system_sessions_auto_dir}+::
299 Directory from which system-wide tracing configuration files are
300 automatically loaded when the session daemon starts (see
301 man:lttng-save(1) and man:lttng-load(1) for saving
302 and loading tracing sessions).
304 `$LTTNG_HOME/.lttng/lttng.conf`::
305 Default location of the session daemon configuration file (see the
306 option:--config option).
308 +{system_lttng_conf}+::
309 System-wide location of the session daemon configuration file (see
310 the option:--config option).
312 NOTE: `$LTTNG_HOME` defaults to `$HOME` when not explicitly set.
329 For an unprivileged user running `lttng-sessiond`, the maximum number of
330 file descriptors per process is usually 1024. This limits the number of
331 traceable applications, since for each instrumented application, there
332 is two file descriptors per CPU and one more socket for bidirectional
335 For the root user, the limit is bumped to 65535. A future version will
336 deal with this limitation.
339 include::common-footer.txt[]