Document tracing session rotation features
[lttng-tools.git] / doc / man / lttng-create.1.txt
1 lttng-create(1)
2 ===============
3
4
5 NAME
6 ----
7 lttng-create - Create an LTTng tracing session
8
9
10 SYNOPSIS
11 --------
12 Local mode:
13
14 [verse]
15 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='PATH']
16 [option:--no-output | option:--output='PATH' | option:--set-url=file://'PATH']
17
18 Network streaming mode:
19
20 [verse]
21 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='PATH']
22 (option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL')
23
24 Snapshot mode:
25
26 [verse]
27 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] option:--snapshot
28 [option:--shm-path='PATH'] [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL']
29
30 Live mode:
31
32 [verse]
33 *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] option:--live[='DELAYUS']
34 [option:--shm-path='PATH'] [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL']
35
36 DESCRIPTION
37 -----------
38 The `lttng create` command creates a new tracing session.
39
40 A tracing session is a named container of channels, which in turn
41 contain event rules. It is domain-agnostic, in that channels and event
42 rules can be enabled for the user space tracer and/or the Linux
43 kernel tracer.
44
45 On execution, an `.lttngrc` file is created, if it does not exist, in the
46 user's home directory. This file contains the name of the current tracing
47 session. When creating a new tracing session with `lttng create`, the
48 current tracing session is set to this new tracing session. The
49 man:lttng-set-session(1) command can be used to set the current
50 tracing session without manually editing the `.lttngrc` file.
51
52 If 'SESSION' is omitted, a session name is automatically created having
53 this form: `auto-YYYYmmdd-HHMMSS`. 'SESSION' *must not* contain the
54 character `/`.
55
56 The option:--shm-path option can be used to specify the path to the
57 shared memory holding the ring buffers. Specifying a location on an
58 NVRAM file system makes it possible to retrieve the latest recorded
59 trace data when the system reboots after a crash. To view the events
60 of ring buffer files after a system crash, use the
61 man:lttng-crash(1) utility.
62
63 Tracing sessions are destroyed using the man:lttng-destroy(1)
64 command.
65
66
67 Creation modes
68 ~~~~~~~~~~~~~~
69 There are four tracing session modes:
70
71 [[local-mode]]Local mode::
72 Traces the local system and writes the trace to the local
73 file system. The option:--output option specifies the trace path.
74 Using option:--set-url=file://'PATH' is the equivalent of using
75 option:--output='PATH'. The file system output can be disabled using
76 the option:--no-output option.
77 +
78 If none of the options mentioned above are used, then the trace is
79 written locally in the `$LTTNG_HOME/lttng-traces` directory
80 (`$LTTNG_HOME` defaults to `$HOME`).
81
82 [[network-streaming-mode]]Network streaming mode::
83 Traces the local system and sends the trace over the network to
84 a listening relay daemon (see man:lttng-relayd(8)).
85 The option:--set-url, or option:--ctrl-url and option:--data-url
86 options set the trace output destination (see the
87 <<url-format,URL format>> section below).
88
89 [[snapshot-mode]]Snapshot mode::
90 Traces the local system without writing the trace to the local file
91 system (implicit option:--no-output option). Channels are automatically
92 configured to be snapshot-ready on creation (see
93 man:lttng-enable-channel(1)). The man:lttng-snapshot(1)
94 command is used to take snapshots of the current ring buffers.
95 The option:--set-url, or option:--ctrl-url and option:--data-url
96 options set the default snapshot output destination.
97
98 [[live-mode]]Live mode::
99 Traces the local system, sending trace data to an LTTng relay daemon
100 over the network (see man:lttng-relayd(8)). The
101 option:--set-url, or option:--ctrl-url and option:--data-url options
102 set the trace output destination. The live output URLs cannot use
103 the `file://` protocol (see the <<url-format,URL format>>
104 section below).
105
106
107 [[url-format]]
108 URL format
109 ~~~~~~~~~~
110 The option:--set-url, option:--ctrl-url, and option:--data-url options'
111 arguments are URLs.
112
113 The format of those URLs is one of:
114
115 [verse]
116 file://'TRACEPATH'
117 'NETPROTO'://('HOST' | 'IPADDR')[:__CTRLPORT__[:__DATAPORT__]][/'TRACEPATH']
118
119 The `file://` protocol targets the *local file system* and can only
120 be used as the option:--set-url option's argument when the session is
121 created in <<local-mode,local>> or <<snapshot-mode,snapshot>> mode.
122
123 'TRACEPATH'::
124 Absolute path to trace files on the local file system.
125
126 The other version is available when the session is created in
127 <<network-streaming-mode,network streaming>>,
128 <<snapshot-mode,snapshot>>, or <<live-mode,live>> mode.
129
130 'NETPROTO'::
131 Network protocol, amongst:
132 +
133 --
134 `net`::
135 TCP over IPv4; the default values of 'CTRLPORT' and 'DATAPORT'
136 are respectively {default_network_control_port} and
137 {default_network_data_port}.
138
139 `net6`::
140 TCP over IPv6: same default ports as the `net` protocol.
141
142 `tcp`::
143 Same as the `net` protocol; can only be used with the
144 option:--ctrl-url and option:--data-url options together.
145
146 `tcp6`::
147 Same as the `net6` protocol; can only be used with the
148 option:--ctrl-url and option:--data-url options together.
149 --
150
151 ('HOST' | 'IPADDR')::
152 Hostname or IP address (IPv6 address *must* be enclosed in brackets
153 (`[` and `]`); see https://www.ietf.org/rfc/rfc2732.txt[RFC 2732]).
154
155 'CTRLPORT'::
156 Control port.
157
158 'DATAPORT'::
159 Data port.
160
161 'TRACEPATH'::
162 Path of trace files on the remote file system. This path is relative
163 to the base output directory set on the relay daemon side;
164 see man:lttng-relayd(8).
165
166
167 include::common-cmd-options-head.txt[]
168
169
170 Mode selection
171 ~~~~~~~~~~~~~~
172 option:--live[='DELAYUS']::
173 Create the session in <<live-mode,live mode>>.
174 +
175 The optional 'DELAYUS' parameter, given in microseconds, is the
176 maximum time the user can wait for the data to be flushed. This mode
177 can be set with a network URL (options option:--set-url, or
178 option:--ctrl-url and option:--data-url) and must have a relay
179 daemon listening (see man:lttng-relayd(8)).
180 +
181 By default, 'DELAYUS' is {default_lttng_live_timer} and the network URL
182 is set to `net://127.0.0.1`.
183
184 option:--snapshot::
185 Create the session in <<snapshot-mode,snapshot mode>>.
186 This is the equivalent of using the option:--no-output option and
187 creating all the channels of this new tracing session in overwrite
188 mode with an `mmap` output type.
189
190
191 Output
192 ~~~~~~
193 option:--no-output::
194 In <<local-mode,local mode>>, do not output any trace data.
195
196 option:-o 'PATH', option:--output='PATH'::
197 In <<local-mode,local mode>>, set trace output path to 'PATH'.
198
199 option:--shm-path='PATH'::
200 Create shared memory holding buffers at 'PATH'.
201
202
203 URL
204 ~~~
205 See the <<url-format,URL format>> section above for more information
206 about the syntax of the following options' 'URL' argument.
207
208 option:-C 'URL', option:--ctrl-url='URL'::
209 Set control path URL to 'URL' (must use option:--data-url option
210 also).
211
212 option:-D 'URL', option:--data-url='URL'::
213 Set data path URL to 'URL' (must use option:--ctrl-url option
214 also).
215
216 option:-U 'URL', option:--set-url='URL'::
217 Set URL destination of the trace data to 'URL'. It is persistent for
218 the session lifetime. This option sets both data
219 (option:--data-url option) and control (option:--ctrl-url option)
220 URLs at the same time.
221 +
222 In <<local-mode,local>> mode, 'URL' must start with `file://` followed
223 by the destination path on the local file system.
224
225
226 include::common-cmd-help-options.txt[]
227
228
229 include::common-cmd-footer.txt[]
230
231
232 SEE ALSO
233 --------
234 man:lttng-destroy(1),
235 man:lttng-set-session(1),
236 man:lttng(1)
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