| 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* ['linkgenoptions:(GENERAL OPTIONS)'] *create* [option:--output='PATH' | option:--no-output] |
| 16 | [option:--shm-path='PATH'] ['SESSION'] |
| 17 | |
| 18 | Snapshot mode: |
| 19 | |
| 20 | [verse] |
| 21 | *lttng* ['linkgenoptions:(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* ['linkgenoptions:(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 | man: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 | man:lttng-crash(1) utility. |
| 59 | |
| 60 | Tracing sessions are destroyed using the man: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 | man:lttng-enable-channel(1)). The man: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 man: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 man: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 man:lttng-relayd(8)). |
| 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 | man:lttng-destroy(1), |
| 200 | man:lttng-set-session(1), |
| 201 | man:lttng(1) |