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ba50d967 PP |
1 | lttng-create(1) |
2 | =============== | |
3 | ||
4 | ||
5 | NAME | |
6 | ---- | |
7 | lttng-create - Create an LTTng tracing session | |
8 | ||
9 | ||
10 | SYNOPSIS | |
11 | -------- | |
12 | Normal mode: | |
13 | ||
14 | [verse] | |
15 | *lttng* ['GENERAL OPTIONS'] *create* [option:--output='PATH' | option:--no-output] | |
16 | [option:--shm-path='PATH'] ['SESSION'] | |
17 | ||
18 | Snapshot mode: | |
19 | ||
20 | [verse] | |
21 | *lttng* ['GENERAL OPTIONS'] *create* option:--snapshot | |
22 | [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL'] | |
23 | [option:--shm-path='PATH'] ['SESSION'] | |
24 | ||
25 | Live mode: | |
26 | ||
27 | [verse] | |
28 | *lttng* ['GENERAL OPTIONS'] *create* option:--live[='DELAYUS'] | |
29 | [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL'] | |
30 | [option:--shm-path='PATH'] ['SESSION'] | |
31 | ||
32 | ||
33 | DESCRIPTION | |
34 | ----------- | |
35 | The `lttng create` command creates a new tracing session. | |
36 | ||
37 | A tracing session is a named container of channels, which in turn | |
38 | contain event rules. It is domain-agnostic, in that channels and event | |
39 | rules can be enabled for the user space tracer and/or the Linux | |
40 | kernel tracer. | |
41 | ||
42 | On execution, an `.lttngrc` file is created, if it does not exist, in the | |
43 | user's home directory. This file contains the name of the current tracing | |
44 | session. When creating a new tracing session with `lttng create`, the | |
45 | current tracing session is set to this new tracing session. The | |
46 | linklttng:lttng-set-session(1) command can be used to set the current | |
47 | tracing session without manually editing the `.lttngrc` file. | |
48 | ||
49 | If 'SESSION' is omitted, a session name is automatically created having | |
50 | this form: `auto-YYYYmmdd-HHMMSS`. 'SESSION' *must not* contain the | |
51 | character `/`. | |
52 | ||
53 | The option:--shm-path option can be used to specify the path to the | |
54 | shared memory holding the ring buffers. Specifying a location on an | |
55 | NVRAM file system makes it possible to retrieve the latest recorded | |
56 | trace data when the system reboots after a crash. To view the events | |
57 | of ring buffer files after a system crash, use the | |
58 | linklttng:lttng-crash(1) utility. | |
59 | ||
60 | Tracing sessions are destroyed using the linklttng:lttng-destroy(1) | |
61 | command. | |
62 | ||
63 | ||
64 | Creation modes | |
65 | ~~~~~~~~~~~~~~ | |
66 | There are three tracing session modes: | |
67 | ||
68 | Normal mode:: | |
69 | Traces the local system and writes the trace to the local | |
70 | file system. The option:--output option specifies the trace path. | |
71 | If omitted, the trace is written in the `$LTTNG_HOME/lttng-traces` | |
72 | directory (`$LTTNG_HOME` defaults to `$HOME`). The file system | |
73 | output can be disabled using the option:--no-output option. | |
74 | ||
75 | Snapshot mode:: | |
76 | Traces the local system without writing the trace to the local file | |
77 | system (implicit option:--no-output option). Channels are automatically | |
78 | configured to be snapshot-ready on creation (see | |
79 | linklttng:lttng-enable-channel(1)). The linklttng:lttng-snapshot(1) | |
80 | command is used to take snapshots of the current ring buffers. | |
81 | The option:--set-url, or option:--ctrl-url and option:--data-url | |
82 | options set the default snapshot output destination. | |
83 | ||
84 | Live mode:: | |
85 | Traces the local system, sending trace data to an LTTng relay daemon | |
86 | over the network (see linklttng:lttng-relayd(8)). The | |
87 | option:--set-url, or option:--ctrl-url and option:--data-url options | |
88 | set the trace output destination. The live output URLs cannot use | |
89 | the `file://` protocol (see URL format below). | |
90 | ||
91 | ||
92 | [[url-format]] | |
93 | URL format | |
94 | ~~~~~~~~~~ | |
95 | The option:--set-url, option:--ctrl-url, and option:--data-url options | |
96 | specify URLs. | |
97 | ||
98 | The format of those URLs is one of: | |
99 | ||
100 | [verse] | |
101 | file://'TRACEPATH' | |
102 | 'NETPROTO'://('HOST' | 'IPADDR')[:__CTRLPORT__[:__DATAPORT__]][/'TRACEPATH'] | |
103 | ||
104 | The `file://` protocol targets the *local file system*. | |
105 | ||
106 | 'TRACEPATH':: | |
107 | Absolute path to trace files on the local file system. | |
108 | ||
109 | The other version is used for *network streaming*. | |
110 | ||
111 | 'NETPROTO':: | |
112 | Network protocol, amongst: | |
113 | + | |
114 | * `net`: TCP over IPv4; the default values of `<ctrl port>` and | |
115 | `<data port>` are resp. 5342 and 5343 | |
116 | * `net6`: TCP over IPv6: same default ports as `net` protocol | |
117 | * `tcp`: same as `net` protocol; can only be used with the | |
118 | option:--ctrl-url and option:--data-url options together | |
119 | * `tcp6`: same as `net6` protocol; can only be used with the | |
120 | option:--ctrl-url and option:--data-url options together | |
121 | ||
122 | ('HOST' | 'IPADDR'):: | |
123 | Hostname or IP address (IPv6 address *must* be enclosed in brackets | |
124 | (`[` and `]`); see https://www.ietf.org/rfc/rfc2732.txt[RFC 2732]). | |
125 | ||
126 | 'CTRLPORT':: | |
127 | Control port. | |
128 | ||
129 | 'DATAPORT':: | |
130 | Data port. | |
131 | ||
132 | 'TRACEPATH':: | |
133 | Path of trace files on the remote file system. This path is relative | |
134 | to the base output directory set on the relay daemon side; | |
135 | see linklttng:lttng-relayd(8). | |
136 | ||
137 | ||
138 | include::common-cmd-options-head.txt[] | |
139 | ||
140 | ||
141 | Mode | |
142 | ~~~~ | |
143 | option:--live[='DELAYUS']:: | |
144 | Create the session in live mode. The optional 'DELAYUS' parameter, | |
145 | given in microseconds, is the maximum time the user can wait for | |
146 | the data to be flushed. This mode can be set with a network URL | |
147 | (options option:--set-url, or option:--ctrl-url and option:--data-url) | |
148 | and must have a relay daemon listening (see linklttng:lttng-relayd(1)). | |
149 | + | |
150 | By default, 'DELAYUS' is 1000000 and the network URL is set to | |
151 | `net://127.0.0.1`. | |
152 | ||
153 | option:--snapshot:: | |
154 | Create the session in snapshot mode. This is the equivalent of using | |
155 | the option:--no-output option and creating all the channels of this | |
156 | new tracing session in overwrite mode with an `mmap` output type. | |
157 | ||
158 | ||
159 | Output | |
160 | ~~~~~~ | |
161 | option:--no-output:: | |
162 | Do not output any trace data. | |
163 | ||
164 | option:-o, option:--output='PATH':: | |
165 | Set trace output path to 'PATH'. | |
166 | ||
167 | option:--shm-path='PATH':: | |
168 | Create shared memory holding buffers at 'PATH'. | |
169 | ||
170 | ||
171 | URL | |
172 | ~~~ | |
173 | See the <<url-format,URL format>> section above for more information | |
174 | about the syntax of the following options' 'URL' argument. | |
175 | ||
176 | option:-C, option:--ctrl-url='URL':: | |
177 | Set control path URL to 'URL' (must use option:--data-url option | |
178 | also). | |
179 | ||
180 | option:-D, option:--data-url='URL':: | |
181 | Set data path URL to 'URL' (must use option:--ctrl-url option | |
182 | also). | |
183 | ||
184 | option:-U, option:--set-url='URL':: | |
185 | Set URL destination of the trace data to 'URL'. It is persistent for | |
186 | the session lifetime. This option sets both data | |
187 | (option:--data-url option) and control (option:--ctrl-url option) | |
188 | URLs at the same time. | |
189 | ||
190 | ||
191 | include::common-cmd-help-options.txt[] | |
192 | ||
193 | ||
194 | include::common-cmd-footer.txt[] | |
195 | ||
196 | ||
197 | SEE ALSO | |
198 | -------- | |
199 | linklttng:lttng-destroy(1), | |
200 | linklttng:lttng-set-session(1), | |
201 | linklttng:lttng(1) |