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[lttng-tools.git] / doc / man / lttng-sessiond.8.txt
1 lttng-sessiond(8)
2 =================
3
4
5 NAME
6 ----
7 lttng-sessiond - LTTng 2 tracing session daemon
8
9
10 SYNOPSIS
11 --------
12 [verse]
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]]
28
29
30 DESCRIPTION
31 -----------
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.
35
36 LTTng consists of Linux kernel modules (for Linux kernel tracing) and
37 dynamically loaded libraries (for user application and library tracing).
38
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).
45
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
50 group name to use.
51
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.
55
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
58 manually.
59
60 NOTE: It is highly recommended to start the session daemon at boot time
61 for stable and long-term tracing.
62
63
64 Automatic loading of tracing session configurations
65 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
66 When the session daemon starts, it automatically loads session
67 configuration files.
68
69 The following directories are searched, non-recursively, in this order
70 for configuration files to load on launch:
71
72 . `$LTTNG_HOME/.lttng/sessions/auto` (`$LTTNG_HOME` defaults to `$HOME`)
73 . +{system_sessions_auto_dir}+
74
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.
78
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.
85
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.
90
91
92 OPTIONS
93 -------
94 Daemon configuration
95 ~~~~~~~~~~~~~~~~~~~~
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
99 descriptors.
100
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
104 open.
105
106 option:-f, option:--config='PATH'::
107 Load session daemon configuration from path 'PATH'.
108
109 option:-g, option:--group='GROUP'::
110 Use 'GROUP' as Unix tracing group (default: `tracing`).
111
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.
116
117 option:-S, option:--sig-parent::
118 Send `SIGUSR1` to parent process to notify readiness.
119 +
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.
124
125
126 Linux kernel tracing
127 ~~~~~~~~~~~~~~~~~~~~
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.
132 +
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
136 module.
137
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).
141 +
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
145 module.
146
147 option:--no-kernel::
148 Disable Linux kernel tracing.
149
150
151 Paths and ports
152 ~~~~~~~~~~~~~~~
153 option:--agent-tcp-port='PORT'::
154 Listen on TCP port 'PORT' for agent application registrations
155 (default: {default_agent_tcp_port}).
156
157 option:-a, option:--apps-sock='PATH'::
158 Set application Unix socket path to 'PATH'.
159
160 option:-c, option:--client-sock='PATH'::
161 Set client Unix socket path to 'PATH'.
162
163 option:--consumerd32-libdir='PATH'::
164 Set 32-bit consumer daemon library directory to 'PATH'.
165
166 option:--consumerd32-path='PATH'::
167 Set 32-bit consumer daemon binary path to 'PATH'.
168
169 option:--consumerd64-libdir='PATH'::
170 Set 64-bit consumer daemon library directory to 'PATH'.
171
172 option:--consumerd64-path='PATH'::
173 Set 64-bit consumer daemon binary path to 'PATH'.
174
175 option:--kconsumerd-cmd-sock='PATH'::
176 Set Linux kernel consumer daemon's command Unix socket path
177 to 'PATH'.
178
179 option:--kconsumerd-err-sock='PATH'::
180 Set Linux kernel consumer daemon's error Unix socket path
181 to 'PATH'.
182
183 option:--ustconsumerd32-cmd-sock='PATH'::
184 Set 32-bit consumer daemon's command Unix socket path to 'PATH'.
185
186 option:--ustconsumerd64-cmd-sock='PATH'::
187 Set 64-bit consumer daemon's command Unix socket path to 'PATH'.
188
189 option:--ustconsumerd32-err-sock='PATH'::
190 Set 32-bit consumer daemon's error Unix socket path to 'PATH'.
191
192 option:--ustconsumerd64-err-sock='PATH'::
193 Set 64-bit consumer daemon's error Unix socket path to 'PATH'.
194
195
196 Verbosity
197 ~~~~~~~~~
198 option:-q, option:--quiet::
199 Suppress all messages, including warnings and errors.
200
201 option:-v, option:--verbose::
202 Increase verbosity.
203 +
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`).
207
208 option:--verbose-consumer::
209 Increase verbosity of consumer daemons spawned by this session
210 daemon.
211
212
213 Program information
214 ~~~~~~~~~~~~~~~~~~~
215 option:-h, option:--help::
216 Show help.
217
218 option:-V, option:--version::
219 Show version.
220
221
222 ENVIRONMENT VARIABLES
223 ---------------------
224 Note that command-line options override their equivalent environment
225 variable.
226
227 `LTTNG_APP_SOCKET_TIMEOUT`::
228 Application socket's timeout (seconds) when sending/receiving
229 commands. After this period of time, the application is unregistered
230 by the session daemon. A value of 0 or -1 means an infinite timeout.
231 Default value: {default_app_socket_rw_timeout}.
232
233 `LTTNG_CONSUMERD32_BIN`::
234 32-bit consumer daemon binary path.
235 +
236 The option:--consumerd32-path option overrides this variable.
237
238 `LTTNG_CONSUMERD32_LIBDIR`::
239 32-bit consumer daemon library path.
240 +
241 The option:--consumerd32-libdir option overrides this variable.
242
243 `LTTNG_CONSUMERD64_BIN`::
244 64-bit consumer daemon binary path.
245 +
246 The option:--consumerd64-path option overrides this variable.
247
248 `LTTNG_CONSUMERD64_LIBDIR`::
249 64-bit consumer daemon library path.
250 +
251 The option:--consumerd64-libdir option overrides this variable.
252
253 `LTTNG_DEBUG_NOCLONE`::
254 Set to 1 to disable the use of `clone()`/`fork()`. Setting this
255 variable is considered insecure, but it is required to allow
256 debuggers to work with the session daemon on some operating systems.
257
258 `LTTNG_EXTRA_KMOD_PROBES`::
259 Load specific LTTng Linux kernel modules when kernel tracing
260 is enabled (option:--no-kernel option is :not: specified), in
261 addition to loading the default list of LTTng kernel modules.
262 +
263 The option:--extra-kmod-probes option overrides this variable.
264
265 `LTTNG_KMOD_PROBES`::
266 Only load specific LTTng Linux kernel modules when kernel tracing
267 is enabled (option:--no-kernel option is :not: specified).
268 +
269 The option:--kmod-probes option overrides this variable.
270
271 `LTTNG_NETWORK_SOCKET_TIMEOUT`::
272 Socket connection, receive and send timeout (milliseconds). A value
273 of 0 or -1 uses the timeout of the operating system (default).
274
275 `LTTNG_SESSION_CONFIG_XSD_PATH`::
276 Tracing session configuration XML schema definition (XSD) path.
277
278
279 FILES
280 -----
281 `$LTTNG_HOME/.lttng`::
282 User LTTng runtime and configuration directory.
283
284 `$LTTNG_HOME/lttng-traces`::
285 Default output directory of LTTng traces. This can be overridden
286 with the nloption:--output option of the man:lttng-create(1)
287 command.
288
289 `$LTTNG_HOME/.lttng/sessions/auto`::
290 Directory from which user tracing configuration files are
291 automatically loaded when the session daemon starts (see
292 man:lttng-save(1) and man:lttng-load(1) for saving
293 and loading tracing sessions).
294
295 +{system_sessions_auto_dir}+::
296 Directory from which system-wide tracing configuration files are
297 automatically loaded when the session daemon starts (see
298 man:lttng-save(1) and man:lttng-load(1) for saving
299 and loading tracing sessions).
300
301 `$LTTNG_HOME/.lttng/lttng.conf`::
302 Default location of the session daemon configuration file (see the
303 option:--config option).
304
305 +{system_lttng_conf}+::
306 System-wide location of the session daemon configuration file (see
307 the option:--config option).
308
309 NOTE: `$LTTNG_HOME` defaults to `$HOME` when not explicitly set.
310
311
312 EXIT STATUS
313 -----------
314 *0*::
315 Success
316
317 *1*::
318 Error
319
320 *3*::
321 Fatal error
322
323
324 LIMITATIONS
325 -----------
326 For an unprivileged user running `lttng-sessiond`, the maximum number of
327 file descriptors per process is usually 1024. This limits the number of
328 traceable applications, since for each instrumented application, there
329 is two file descriptors per CPU and one more socket for bidirectional
330 communication.
331
332 For the root user, the limit is bumped to 65535. A future version will
333 deal with this limitation.
334
335
336 include::common-footer.txt[]
337
338
339 SEE ALSO
340 --------
341 man:lttng(1),
342 man:lttng-relayd(8),
343 man:lttng-crash(1),
344 man:lttng-ust(3),
345 man:babeltrace(1)
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