1LTTNG(1) LTTng Manual LTTNG(1)
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6 lttng - Control LTTng tracing
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9 lttng [--group=GROUP] [--mi=xml] [--no-sessiond | --sessiond-path=PATH]
10 [--relayd-path=PATH] [--quiet | -verbose...]
11 COMMAND [COMMAND OPTIONS]
12
14 The Linux Trace Toolkit: next generation <https://lttng.org/> is an
15 open-source software package used for correlated tracing of the Linux
16 kernel, user applications, and user libraries.
17 LTTng consists of Linux kernel modules (for Linux kernel tracing) and
19 dynamically loaded libraries (for user application and library
20 tracing).
21 The lttng command-line tool, as well as any user application linked
23 with the LTTng control library (liblttng-ctl), sends commands to a
24 listening LTTng session daemon (lttng-sessiond(8)). A session daemon:
25 • Manages recording sessions (see lttng-concepts(7) to learn more
27 about recording sessions).
28 • Controls the various components (like tracers and consumer daemons)
30 of LTTng.
31 • Sends asynchronous notifications to user applications.
33 By default, the lttng-create(1) command automatically spawns:
35 • A session daemon for your Unix user if none is currently running.
37 Override the path of the session daemon binary to spawn with the
39 --sessiond-path option.
40 Avoid automatically spawning a session daemon with the --no-
42 sessiond option.
43 • A relay daemon (see lttng-relayd(8)) if all the following
45 statements are true:
46 • You specify the --live option.
48 • You don’t specify any of the --set-url, --ctrl-url, or --data-
50 url options.
51 • No relay daemon is currently listening for TCP connections on
53 127.0.0.1:5344 (default LTTng live reader connection address
54 and port).
55 Override the path of the relay daemon binary to spawn with the
57 --relayd-path option.
58 Note
60 The LTTng project recommends that you start the session daemon at
61 boot time for stable and long-term tracing.
62 See lttng-concepts(7) to learn more about the foundational concepts of
64 LTTng.
65 The lttng tool offers a subcommand-based command-line interface. The
67 “COMMANDS” section below lists the available commands.
68 Session daemon connection
70 For most of its commands, the lttng tool needs to connect to a
71 listening LTTng session daemon (lttng-sessiond(8)) to control LTTng
72 tracing.
73 Each Unix user may have its own independent running session daemon.
75 However, the lttng tool must connect to the session daemon of the root
76 user (the root session daemon) to control Linux kernel tracing.
77 How the lttng tool chooses which session daemon to connect to is as
79 follows:
80 If your Unix user is root
82 Connect to the root session daemon.
83 If your Unix user is not root
85 If your Unix user is part of the Unix tracing group
87 Try to connect to the root session daemon.
88 If the root session daemon isn’t running, connect to the
90 session daemon of your Unix user.
91 If your Unix user is not part of the tracing group
93 Connect to the session daemon of your Unix user.
94 The name of the Unix tracing group is one of:
96 With the --group=GROUP option of the root session daemon (lttng-
98 sessiond(8))
99 GROUP
100 In that case, you must use the --group=GROUP option, with the same
102 GROUP argument, of the lttng tool.
103 Without the --group option of the root session daemon
105 tracing
106 LTTng-instrumented user applications automatically register to both the
108 root and user session daemons. This makes it possible for both session
109 daemons to list the available instrumented applications and their
110 instrumentation points (see lttng-list(1)).
111
113 -g GROUP, --group=GROUP
114 Set the name of the Unix tracing group to GROUP instead of tracing.
115 You must use this option to be able to connect to a root session
117 daemon (lttng-sessiond(8)) which was started with its own
118 --group=GROUP option.
119 -m xml, --mi=xml
121 Print the command’s result using a stable XML machine interface
122 (MI) output instead of the default, unstable human-readable output.
123 With this mode, lttng prints the resulting XML document to the
125 standard output, while it prints any error/warning to the standard
126 error with an unstable, human-readable format.
127 If any error occurs during the execution of lttng, the command
129 exits with a status different than 0, and lttng does NOT guarantee
130 the syntax and data validity of its MI output.
131 An XML schema definition (XSD) file used for validation of the MI
133 output is available: see the src/common/mi_lttng.xsd file in the
134 LTTng-tools source tree.
135 -n, --no-sessiond
137 Do not automatically spawn a session daemon for your Unix user when
138 running the lttng-create(1) command.
139 You may NOT use this option with the --sessiond-path option.
141 -q, --quiet
143 Suppress all messages, including warnings and errors.
144 You may NOT use this option with the --verbose option.
146 --sessiond-path=PATH
148 Set the absolute path of the session daemon binary to spawn from
149 the lttng-create(1) command to PATH.
150 You may NOT use this option with the --no-sessiond option.
152 --relayd-path=PATH
154 Set the absolute path of the relay daemon binary to spawn from the
155 lttng-create(1) command to PATH.
156 -v, --verbose
158 Increase verbosity.
159 Specify this option up to three times to get more levels of
161 verbosity.
162 You may NOT use this option with the --quiet option.
164 Program information
166 -h, --help
167 Show help.
168 This option attempts to launch /usr/bin/man to view this manual
170 page. Override the manual pager path with the LTTNG_MAN_BIN_PATH
171 environment variable.
172 --list-options
174 List available command options and quit.
175 --list-commands
177 List available commands and quit.
178 -V, --version
180 Show version and quit.
181
183 The following commands also have their own --help option.
184 Recording session
186 ┌──────────────────────────┬────────────────────────────┐
187 │Command │ Description │
188 ├──────────────────────────┼────────────────────────────┤
189 │ │ │
190 │lttng-create(1) │ Create a recording │
191 │ │ session. │
192 ├──────────────────────────┼────────────────────────────┤
193 │ │ │
194 │lttng-destroy(1) │ Destroy recording │
195 │ │ sessions. │
196 ├──────────────────────────┼────────────────────────────┤
197 │ │ │
198 │lttng-disable-rotation(1) │ Unset a recording session │
199 │ │ rotation schedule. │
200 ├──────────────────────────┼────────────────────────────┤
201 │ │ │
202 │lttng-enable-rotation(1) │ Set a recording session │
203 │ │ rotation schedule. │
204 ├──────────────────────────┼────────────────────────────┤
205 │ │ │
206 │lttng-load(1) │ Load recording session │
207 │ │ configurations. │
208 ├──────────────────────────┼────────────────────────────┤
209 │ │ │
210 │lttng-regenerate(1) │ Regenerate specific │
211 │ │ recording session data. │
212 ├──────────────────────────┼────────────────────────────┤
213 │ │ │
214 │lttng-rotate(1) │ Archive the current trace │
215 │ │ chunk of a recording │
216 │ │ session. │
217 ├──────────────────────────┼────────────────────────────┤
218 │ │ │
219 │lttng-save(1) │ Save recording session │
220 │ │ configurations. │
221 ├──────────────────────────┼────────────────────────────┤
222 │ │ │
223 │lttng-set-session(1) │ Set the current recording │
224 │ │ session. │
225 ├──────────────────────────┼────────────────────────────┤
226 │ │ │
227 │lttng-snapshot(1) │ Take a recording session │
228 │ │ snapshot. │
229 ├──────────────────────────┼────────────────────────────┤
230 │ │ │
231 │lttng-start(1) │ Start a recording session. │
232 ├──────────────────────────┼────────────────────────────┤
233 │ │ │
234 │lttng-status(1) │ Show the status of the │
235 │ │ current recording session. │
236 ├──────────────────────────┼────────────────────────────┤
237 │ │ │
238 │lttng-stop(1) │ Stop a recording session. │
239 └──────────────────────────┴────────────────────────────┘
240 Channel
242 ┌─────────────────────────┬──────────────────────────┐
243 │Command │ Description │
244 ├─────────────────────────┼──────────────────────────┤
245 │ │ │
246 │lttng-add-context(1) │ Add context fields to be │
247 │ │ recorded. │
248 ├─────────────────────────┼──────────────────────────┤
249 │ │ │
250 │lttng-disable-channel(1) │ Disable channels. │
251 ├─────────────────────────┼──────────────────────────┤
252 │ │ │
253 │lttng-enable-channel(1) │ Create or enable a │
254 │ │ channel. │
255 └─────────────────────────┴──────────────────────────┘
256 Recording event rule
258 ┌───────────────────────┬────────────────────────────┐
259 │Command │ Description │
260 ├───────────────────────┼────────────────────────────┤
261 │ │ │
262 │lttng-disable-event(1) │ Disable recording event │
263 │ │ rules. │
264 ├───────────────────────┼────────────────────────────┤
265 │ │ │
266 │lttng-enable-event(1) │ Create or enable recording │
267 │ │ event rules. │
268 └───────────────────────┴────────────────────────────┘
269 Information
271 ┌──────────────┬─────────────────────────┐
272 │Command │ Description │
273 ├──────────────┼─────────────────────────┤
274 │ │ │
275 │lttng-list(1) │ List recording sessions │
276 │ │ and instrumentation │
277 │ │ points. │
278 └──────────────┴─────────────────────────┘
279 Resource tracking
281 ┌─────────────────┬──────────────────────────┐
282 │Command │ Description │
283 ├─────────────────┼──────────────────────────┤
284 │ │ │
285 │lttng-track(1) │ Allow specific processes │
286 │ │ to record events. │
287 ├─────────────────┼──────────────────────────┤
288 │ │ │
289 │lttng-untrack(1) │ Disallow specific │
290 │ │ processes to record │
291 │ │ events. │
292 └─────────────────┴──────────────────────────┘
293 Trigger
295 ┌────────────────────────┬───────────────────┐
296 │Command │ Description │
297 ├────────────────────────┼───────────────────┤
298 │ │ │
299 │lttng-add-trigger(1) │ Add a trigger. │
300 ├────────────────────────┼───────────────────┤
301 │ │ │
302 │lttng-list-triggers(1) │ List triggers. │
303 ├────────────────────────┼───────────────────┤
304 │ │ │
305 │lttng-remove-trigger(1) │ Remove a trigger. │
306 └────────────────────────┴───────────────────┘
307 Miscellaneous
309 ┌─────────────────┬──────────────────────────┐
310 │Command │ Description │
311 ├─────────────────┼──────────────────────────┤
312 │ │ │
313 │lttng-help(1) │ Show the help of a │
314 │ │ command. │
315 ├─────────────────┼──────────────────────────┤
316 │ │ │
317 │lttng-version(1) │ Show LTTng-tools version │
318 │ │ information. │
319 ├─────────────────┼──────────────────────────┤
320 │ │ │
321 │lttng-view(1) │ Launch a trace reader. │
322 └─────────────────┴──────────────────────────┘
323
325 0
326 Success
327 1
329 Command error
330 2
332 Undefined command
333 3
335 Fatal error
336 4
338 Command warning (something went wrong during the command)
339
341 LTTNG_ABORT_ON_ERROR
342 Set to 1 to abort the process after the first error is encountered.
343 LTTNG_HOME
345 Path to the LTTng home directory.
346 Defaults to $HOME.
348 Useful when the Unix user running the commands has a non-writable
350 home directory.
351 LTTNG_MAN_BIN_PATH
353 Absolute path to the manual pager to use to read the LTTng
354 command-line help (with lttng-help(1) or with the --help option)
355 instead of /usr/bin/man.
356 LTTNG_SESSION_CONFIG_XSD_PATH
358 Path to the directory containing the session.xsd recording session
359 configuration XML schema.
360 LTTNG_SESSIOND_PATH
362 Absolute path to the LTTng session daemon binary (see lttng-
363 sessiond(8)) to spawn from the lttng-create(1) command.
364 The --sessiond-path general option overrides this environment
366 variable.
367
369 $LTTNG_HOME/.lttngrc
370 Unix user’s LTTng runtime configuration.
371 This is where LTTng stores the name of the Unix user’s current
373 recording session between executions of lttng(1). lttng-create(1)
374 and lttng-set-session(1) set the current recording session.
375 $LTTNG_HOME/lttng-traces
377 Default output directory of LTTng traces in local and snapshot
378 modes.
379 Override this path with the --output option of the lttng-create(1)
381 command.
382 $LTTNG_HOME/.lttng
384 Unix user’s LTTng runtime and configuration directory.
385 $LTTNG_HOME/.lttng/sessions
387 Default directory containing the Unix user’s saved recording
388 session configurations (see lttng-save(1) and lttng-load(1)).
389 /usr/local/etc/lttng/sessions
391 Directory containing the system-wide saved recording session
392 configurations (see lttng-save(1) and lttng-load(1)).
393 Note
395 $LTTNG_HOME defaults to the value of the HOME environment variable.
396
398 • LTTng project website <https://lttng.org>
399 • LTTng documentation <https://lttng.org/docs>
401 • LTTng bug tracker <https://bugs.lttng.org>
403 • Git repositories <https://git.lttng.org>
405 • GitHub organization <https://github.com/lttng>
407 • Continuous integration <https://ci.lttng.org/>
409 • Mailing list <https://lists.lttng.org/> for support and
411 development: lttng-dev@lists.lttng.org
412 • IRC channel <irc://irc.oftc.net/lttng>: #lttng on irc.oftc.net
414
416 This program is part of the LTTng-tools project.
417 LTTng-tools is distributed under the GNU General Public License
419 version 2 <http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html>.
420 See the LICENSE <https://github.com/lttng/lttng-
421 tools/blob/master/LICENSE> file for details.
422
424 Special thanks to Michel Dagenais and the DORSAL laboratory
425 <http://www.dorsal.polymtl.ca/> at École Polytechnique de Montréal for
426 the LTTng journey.
427 Also thanks to the Ericsson teams working on tracing which helped us
429 greatly with detailed bug reports and unusual test cases.
430
432 lttng-concepts(7) lttng-relayd(8), lttng-sessiond(8)
433LTTng 2.13.10 14 June 2021 LTTNG(1)