| 1 | lttng-create(1) |
| 2 | =============== |
| 3 | :revdate: 8 April 2021 |
| 4 | |
| 5 | |
| 6 | NAME |
| 7 | ---- |
| 8 | lttng-create - Create an LTTng tracing session |
| 9 | |
| 10 | |
| 11 | SYNOPSIS |
| 12 | -------- |
| 13 | Create a local mode tracing session: |
| 14 | |
| 15 | [verse] |
| 16 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='DIR'] |
| 17 | [option:--no-output | option:--output='DIR' | option:--set-url=file://'DIR'] |
| 18 | |
| 19 | Create a network streaming mode tracing session: |
| 20 | |
| 21 | [verse] |
| 22 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='DIR'] |
| 23 | (option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL') |
| 24 | |
| 25 | Create a snapshot mode tracing session: |
| 26 | |
| 27 | [verse] |
| 28 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] option:--snapshot |
| 29 | [option:--shm-path='DIR'] [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL'] |
| 30 | |
| 31 | Create a live mode tracing session: |
| 32 | |
| 33 | [verse] |
| 34 | *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] option:--live[='DELAYUS'] |
| 35 | [option:--shm-path='DIR'] [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL'] |
| 36 | |
| 37 | DESCRIPTION |
| 38 | ----------- |
| 39 | The `lttng create` command creates a new tracing session for your Unix |
| 40 | user. |
| 41 | |
| 42 | A tracing session is a stateful dialogue between you and a |
| 43 | session daemon (see man:lttng-sessiond(8)) for everything related to |
| 44 | event recording. |
| 45 | |
| 46 | Everything that you do when you control LTTng tracers to record events |
| 47 | happens within a tracing session. In particular, a tracing session: |
| 48 | |
| 49 | * Has its own name. |
| 50 | |
| 51 | * Has its own set of trace files, if any. |
| 52 | |
| 53 | * Has its own state of activity (started or stopped). |
| 54 | |
| 55 | * Has its own mode (local, network streaming, |
| 56 | snapshot, or live). |
| 57 | + |
| 58 | See the <<modes,Tracing session modes>> section below to learn more. |
| 59 | |
| 60 | * Has its own channels (see man:lttng-enable-channel(1)) to which are |
| 61 | attached their own recording event rules (see |
| 62 | man:lttng-enable-event(1)). |
| 63 | |
| 64 | * Has its own process attribute tracking inclusion sets (see |
| 65 | man:lttng-track(1)). |
| 66 | |
| 67 | Without the 'SESSION' argument, LTTng automatically generates a tracing |
| 68 | session name having the ++auto-++__YYYYmmdd__++-++__HHMMSS__ form, where |
| 69 | 'YYYYmmdd' and 'HHMMSS' are the creation date and time. 'SESSION' may |
| 70 | :not: contain the character `/`. |
| 71 | |
| 72 | Specify the path of the directory containing the shared memory files |
| 73 | holding the channel ring buffers with the option:--shm-path option. |
| 74 | Specifying a location on an NVRAM file system makes it possible to |
| 75 | recover the latest recorded trace data when the system reboots after a |
| 76 | crash with the man:lttng-crash(1) utility. |
| 77 | |
| 78 | By default, the `create` command automatically spawns a session daemon |
| 79 | for your Unix user if none is currently running. Override the path of |
| 80 | the session daemon binary to spawn with the general |
| 81 | genoption:--sessiond-path option. Avoid automatically spawning a session |
| 82 | daemon with the general genoption:--no-sessiond option. |
| 83 | |
| 84 | List the tracing sessions of your Unix user with the man:lttng-list(1) |
| 85 | command. |
| 86 | |
| 87 | Start and stop a tracing session with the man:lttng-start(1) and |
| 88 | man:lttng-stop(1) commands. |
| 89 | |
| 90 | Save and load a tracing session with the man:lttng-save(1) and |
| 91 | man:lttng-load(1) commands. |
| 92 | |
| 93 | Archive the current trace chunk (rotate) a tracing session with the |
| 94 | man:lttng-rotate(1) command. |
| 95 | |
| 96 | Destroy a tracing session with the man:lttng-destroy(1) command. |
| 97 | |
| 98 | |
| 99 | Current tracing session |
| 100 | ~~~~~~~~~~~~~~~~~~~~~~~ |
| 101 | When you run the `create` command, LTTng creates the |
| 102 | `$LTTNG_HOME/.lttngrc` file if it doesn't exist (`$LTTNG_HOME` defaults |
| 103 | to `$HOME`). |
| 104 | |
| 105 | `$LTTNG_HOME/.lttngrc` contains the name of the _current tracing |
| 106 | session_. |
| 107 | |
| 108 | When you create a new tracing session with the `create` command, LTTng |
| 109 | updates the current tracing session. |
| 110 | |
| 111 | The following man:lttng(1) commands select the current tracing session |
| 112 | if you don't specify one: |
| 113 | |
| 114 | * man:lttng-add-context(1) |
| 115 | * man:lttng-clear(1) |
| 116 | * man:lttng-destroy(1) |
| 117 | * man:lttng-disable-channel(1) |
| 118 | * man:lttng-disable-event(1) |
| 119 | * man:lttng-disable-rotation(1) |
| 120 | * man:lttng-enable-channel(1) |
| 121 | * man:lttng-enable-event(1) |
| 122 | * man:lttng-enable-rotation(1) |
| 123 | * man:lttng-regenerate(1) |
| 124 | * man:lttng-rotate(1) |
| 125 | * man:lttng-save(1) |
| 126 | * man:lttng-snapshot(1) |
| 127 | * man:lttng-start(1) |
| 128 | * man:lttng-status(1) |
| 129 | * man:lttng-stop(1) |
| 130 | * man:lttng-track(1) |
| 131 | * man:lttng-untrack(1) |
| 132 | * man:lttng-view(1) |
| 133 | |
| 134 | Set the current tracing session manually with the |
| 135 | man:lttng-set-session(1) command, without having to edit the `.lttngrc` |
| 136 | file. |
| 137 | |
| 138 | |
| 139 | [[modes]] |
| 140 | Tracing session modes |
| 141 | ~~~~~~~~~~~~~~~~~~~~~ |
| 142 | LTTng offers four tracing session modes: |
| 143 | |
| 144 | [[local-mode]]Local mode:: |
| 145 | Write the trace data to the local file system. |
| 146 | + |
| 147 | The option:--output option specifies the trace path. Using |
| 148 | option:--set-url=++file://++__DIR__ is equivalent to using |
| 149 | option:--output='DIR'. |
| 150 | + |
| 151 | Disable the file system output with the |
| 152 | option:--no-output option. |
| 153 | + |
| 154 | If you don't use any of the option:--output, option:--set-url, or |
| 155 | option:--no-output options, then LTTng writes the trace data locally to |
| 156 | the `$LTTNG_HOME/lttng-traces` directory (`$LTTNG_HOME` defaults to |
| 157 | `$HOME`). |
| 158 | |
| 159 | [[network-streaming-mode]]Network streaming mode:: |
| 160 | Send the trace data over the network to a listening relay daemon |
| 161 | (see man:lttng-relayd(8)). |
| 162 | + |
| 163 | Set the trace output destination with the option:--set-url option, or |
| 164 | with the option:--ctrl-url and option:--data-url options (see the |
| 165 | <<url-format,URL format>> section below). |
| 166 | |
| 167 | [[snapshot-mode]]Snapshot mode (option:--snapshot option):: |
| 168 | Don't write the trace data to the local file system by default |
| 169 | (implicit option:--no-output option): only write the trace data to |
| 170 | the local file system or send it to a listening relay daemon |
| 171 | (man:lttng-relayd(8)) when LTTng takes a snapshot. |
| 172 | + |
| 173 | LTTng automatically configures the channels of such a tracing session to |
| 174 | be snapshot-ready on creation (see man:lttng-enable-channel(1)). |
| 175 | + |
| 176 | LTTng takes a snapshot of such a tracing session when: |
| 177 | + |
| 178 | -- |
| 179 | * You run the man:lttng-snapshot(1) command. |
| 180 | * LTTng executes a `snapshot-session` trigger action (see |
| 181 | man:lttng-add-trigger(1)). |
| 182 | -- |
| 183 | + |
| 184 | Set the default snapshot output destination with the |
| 185 | option:--set-url option, or with the option:--ctrl-url and |
| 186 | option:--data-url options (see the <<url-format,URL format>> section |
| 187 | below). |
| 188 | |
| 189 | [[live-mode]]Live mode (option:--live option):: |
| 190 | Send the trace data over the network to a listening relay daemon |
| 191 | (see man:lttng-relayd(8)) for live reading. |
| 192 | + |
| 193 | Set the trace output destination with the option:--set-url='URL' option, |
| 194 | or with the option:--ctrl-url='URL' and option:--data-url='URL' options |
| 195 | (see the <<url-format,URL format>> section below). 'URL' may :not: start |
| 196 | with `file://`. |
| 197 | |
| 198 | |
| 199 | [[url-format]] |
| 200 | URL format |
| 201 | ~~~~~~~~~~ |
| 202 | The argument of the option:--set-url, option:--ctrl-url, and |
| 203 | option:--data-url options is an URL. |
| 204 | |
| 205 | There are two available URL formats. |
| 206 | |
| 207 | Local format:: |
| 208 | + |
| 209 | [verse] |
| 210 | file://'TRACEDIR' |
| 211 | {nbsp} |
| 212 | + |
| 213 | The `file://` protocol targets the *local file system*: you may only use |
| 214 | such an URL with the option:--set-url option when you create the tracing |
| 215 | session in local or snapshot mode (see the <<modes,Tracing session |
| 216 | modes>> section above). |
| 217 | + |
| 218 | 'TRACEDIR'::: |
| 219 | Absolute path to the directory containing the trace data on the |
| 220 | local file system. |
| 221 | |
| 222 | Network format:: |
| 223 | + |
| 224 | [verse] |
| 225 | 'NETPROTO'://('HOST' | 'IPADDR')[:__CTRLPORT__[:__DATAPORT__]][/'TRACEDIR'] |
| 226 | {nbsp} |
| 227 | + |
| 228 | This format is only available when you create the tracing session in |
| 229 | network streaming, snapshot, or live mode (see the <<modes,Tracing |
| 230 | session modes>> section above). |
| 231 | + |
| 232 | 'NETPROTO'::: |
| 233 | Network protocol, amongst: |
| 234 | + |
| 235 | -- |
| 236 | `net`:: |
| 237 | TCP over IPv4. |
| 238 | + |
| 239 | The default values of 'CTRLPORT' and 'DATAPORT' |
| 240 | are respectively {default_network_control_port} and |
| 241 | {default_network_data_port}. |
| 242 | |
| 243 | `net6`:: |
| 244 | TCP over IPv6. |
| 245 | + |
| 246 | The default values of 'CTRLPORT' and 'DATAPORT' |
| 247 | are respectively {default_network_control_port} and |
| 248 | {default_network_data_port}. |
| 249 | |
| 250 | `tcp`:: |
| 251 | Same as the `net` protocol. |
| 252 | + |
| 253 | You may only use this with the option:--ctrl-url and option:--data-url |
| 254 | options together. |
| 255 | |
| 256 | `tcp6`:: |
| 257 | Same as the `net6` protocol. |
| 258 | + |
| 259 | You can only be use this with the option:--ctrl-url and |
| 260 | option:--data-url options together. |
| 261 | -- |
| 262 | + |
| 263 | ('HOST' | 'IPADDR')::: |
| 264 | Hostname or IP address (IPv6 address *must* be enclosed in square |
| 265 | brackets (`[` and{nbsp}`]`); see |
| 266 | https://www.ietf.org/rfc/rfc2732.txt[RFC{nbsp}2732]). |
| 267 | |
| 268 | 'CTRLPORT'::: |
| 269 | Control TCP port. |
| 270 | |
| 271 | 'DATAPORT'::: |
| 272 | Data TCP port. |
| 273 | |
| 274 | 'TRACEDIR'::: |
| 275 | Path of the directory containing the trace data on the remote file |
| 276 | system. |
| 277 | + |
| 278 | This path is relative to the base output directory of the LTTng relay |
| 279 | daemon (see the nloption:--output option of man:lttng-relayd(8)). |
| 280 | |
| 281 | |
| 282 | include::common-cmd-options-head.txt[] |
| 283 | |
| 284 | |
| 285 | Mode selection |
| 286 | ~~~~~~~~~~~~~~ |
| 287 | See the <<modes,Tracing session modes>> section above. |
| 288 | |
| 289 | At most one of: |
| 290 | |
| 291 | option:--live[='DELAYUS']:: |
| 292 | Create the tracing session in live mode. |
| 293 | + |
| 294 | The optional 'DELAYUS' argument is the maximum time (in µs) you can wait |
| 295 | for the data to be flushed (sent to the connected LTTng relay daemon). |
| 296 | The default value of 'DELAYUS' is {default_lttng_live_timer}. |
| 297 | + |
| 298 | Set the URL of the relay daemon to connect to with the option:--set-url |
| 299 | option, or with the option:--ctrl-url and option:--data-url options, |
| 300 | instead of using `net://127.0.0.1`. |
| 301 | + |
| 302 | The session daemon must be able to connect to a listening relay daemon |
| 303 | (see man:lttng-relayd(8)). |
| 304 | |
| 305 | option:--snapshot:: |
| 306 | Create the tracing session in snapshot mode. |
| 307 | + |
| 308 | This is equivalent to using the option:--no-output option and creating |
| 309 | all the channels of this new tracing session with the |
| 310 | nloption:--override and nloption:--output=++mmap++ options (see |
| 311 | man:lttng-enable-channel(1)). |
| 312 | |
| 313 | |
| 314 | Output |
| 315 | ~~~~~~ |
| 316 | option:--no-output:: |
| 317 | In local mode (see the <<modes,Tracing session modes>> section |
| 318 | above), do :not: write any trace data. |
| 319 | + |
| 320 | You may :not: use this option with the option:--output option. |
| 321 | |
| 322 | option:-o 'DIR', option:--output='DIR':: |
| 323 | In local mode, set the trace output path to 'DIR'. |
| 324 | + |
| 325 | You may :not: use this option with the option:--no-output option. |
| 326 | |
| 327 | option:--shm-path='DIR':: |
| 328 | Set the path of the directory containing the shared memory files |
| 329 | holding the channel ring buffers to 'DIR' on the local file sytem. |
| 330 | |
| 331 | |
| 332 | URL |
| 333 | ~~~ |
| 334 | See the <<url-format,URL format>> section above to learn more about the |
| 335 | syntax of the 'URL' argument of the following options. |
| 336 | |
| 337 | option:-C 'URL', option:--ctrl-url='URL':: |
| 338 | Set the control path URL to 'URL'. |
| 339 | + |
| 340 | You must also use the option:--data-url option. |
| 341 | |
| 342 | option:-D 'URL', option:--data-url='URL':: |
| 343 | Set the trace data path URL to 'URL'. |
| 344 | + |
| 345 | You must also use the option:--ctrl-url option. |
| 346 | |
| 347 | option:-U 'URL', option:--set-url='URL':: |
| 348 | Set the destination URL of the control path and trace data to 'URL'. |
| 349 | + |
| 350 | This URL stays the same as long as the tracing session exists. |
| 351 | + |
| 352 | In local mode (see the <<modes,Tracing session modes>> section above), |
| 353 | 'URL' must start with `file://`, followed with the destination directory |
| 354 | path on the local file system. |
| 355 | |
| 356 | |
| 357 | include::common-cmd-help-options.txt[] |
| 358 | |
| 359 | |
| 360 | include::common-cmd-footer.txt[] |
| 361 | |
| 362 | |
| 363 | SEE ALSO |
| 364 | -------- |
| 365 | man:lttng(1), |
| 366 | man:lttng-destroy(1), |
| 367 | man:lttng-enable-channel(1), |
| 368 | man:lttng-relayd(8), |
| 369 | man:lttng-rotate(1), |
| 370 | man:lttng-sessiond(8), |
| 371 | man:lttng-set-session(1), |
| 372 | man:lttng-start(1), |
| 373 | man:lttng-stop(1), |
| 374 | man:lttng-track(1) |