lttng-create(1) =============== NAME ---- lttng-create - Create an LTTng tracing session SYNOPSIS -------- Normal mode: [verse] *lttng* ['GENERAL OPTIONS'] *create* [option:--output='PATH' | option:--no-output] [option:--shm-path='PATH'] ['SESSION'] Snapshot mode: [verse] *lttng* ['GENERAL OPTIONS'] *create* option:--snapshot [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL'] [option:--shm-path='PATH'] ['SESSION'] Live mode: [verse] *lttng* ['GENERAL OPTIONS'] *create* option:--live[='DELAYUS'] [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL'] [option:--shm-path='PATH'] ['SESSION'] DESCRIPTION ----------- The `lttng create` command creates a new tracing session. A tracing session is a named container of channels, which in turn contain event rules. It is domain-agnostic, in that channels and event rules can be enabled for the user space tracer and/or the Linux kernel tracer. On execution, an `.lttngrc` file is created, if it does not exist, in the user's home directory. This file contains the name of the current tracing session. When creating a new tracing session with `lttng create`, the current tracing session is set to this new tracing session. The linklttng:lttng-set-session(1) command can be used to set the current tracing session without manually editing the `.lttngrc` file. If 'SESSION' is omitted, a session name is automatically created having this form: `auto-YYYYmmdd-HHMMSS`. 'SESSION' *must not* contain the character `/`. The option:--shm-path option can be used to specify the path to the shared memory holding the ring buffers. Specifying a location on an NVRAM file system makes it possible to retrieve the latest recorded trace data when the system reboots after a crash. To view the events of ring buffer files after a system crash, use the linklttng:lttng-crash(1) utility. Tracing sessions are destroyed using the linklttng:lttng-destroy(1) command. Creation modes ~~~~~~~~~~~~~~ There are three tracing session modes: Normal mode:: Traces the local system and writes the trace to the local file system. The option:--output option specifies the trace path. If omitted, the trace is written in the `$LTTNG_HOME/lttng-traces` directory (`$LTTNG_HOME` defaults to `$HOME`). The file system output can be disabled using the option:--no-output option. Snapshot mode:: Traces the local system without writing the trace to the local file system (implicit option:--no-output option). Channels are automatically configured to be snapshot-ready on creation (see linklttng:lttng-enable-channel(1)). The linklttng:lttng-snapshot(1) command is used to take snapshots of the current ring buffers. The option:--set-url, or option:--ctrl-url and option:--data-url options set the default snapshot output destination. Live mode:: Traces the local system, sending trace data to an LTTng relay daemon over the network (see linklttng:lttng-relayd(8)). The option:--set-url, or option:--ctrl-url and option:--data-url options set the trace output destination. The live output URLs cannot use the `file://` protocol (see URL format below). [[url-format]] URL format ~~~~~~~~~~ The option:--set-url, option:--ctrl-url, and option:--data-url options specify URLs. The format of those URLs is one of: [verse] file://'TRACEPATH' 'NETPROTO'://('HOST' | 'IPADDR')[:__CTRLPORT__[:__DATAPORT__]][/'TRACEPATH'] The `file://` protocol targets the *local file system*. 'TRACEPATH':: Absolute path to trace files on the local file system. The other version is used for *network streaming*. 'NETPROTO':: Network protocol, amongst: + * `net`: TCP over IPv4; the default values of `` and `` are resp. 5342 and 5343 * `net6`: TCP over IPv6: same default ports as `net` protocol * `tcp`: same as `net` protocol; can only be used with the option:--ctrl-url and option:--data-url options together * `tcp6`: same as `net6` protocol; can only be used with the option:--ctrl-url and option:--data-url options together ('HOST' | 'IPADDR'):: Hostname or IP address (IPv6 address *must* be enclosed in brackets (`[` and `]`); see https://www.ietf.org/rfc/rfc2732.txt[RFC 2732]). 'CTRLPORT':: Control port. 'DATAPORT':: Data port. 'TRACEPATH':: Path of trace files on the remote file system. This path is relative to the base output directory set on the relay daemon side; see linklttng:lttng-relayd(8). include::common-cmd-options-head.txt[] Mode ~~~~ option:--live[='DELAYUS']:: Create the session in live mode. The optional 'DELAYUS' parameter, given in microseconds, is the maximum time the user can wait for the data to be flushed. This mode can be set with a network URL (options option:--set-url, or option:--ctrl-url and option:--data-url) and must have a relay daemon listening (see linklttng:lttng-relayd(1)). + By default, 'DELAYUS' is 1000000 and the network URL is set to `net://127.0.0.1`. option:--snapshot:: Create the session in snapshot mode. This is the equivalent of using the option:--no-output option and creating all the channels of this new tracing session in overwrite mode with an `mmap` output type. Output ~~~~~~ option:--no-output:: Do not output any trace data. option:-o, option:--output='PATH':: Set trace output path to 'PATH'. option:--shm-path='PATH':: Create shared memory holding buffers at 'PATH'. URL ~~~ See the <> section above for more information about the syntax of the following options' 'URL' argument. option:-C, option:--ctrl-url='URL':: Set control path URL to 'URL' (must use option:--data-url option also). option:-D, option:--data-url='URL':: Set data path URL to 'URL' (must use option:--ctrl-url option also). option:-U, option:--set-url='URL':: Set URL destination of the trace data to 'URL'. It is persistent for the session lifetime. This option sets both data (option:--data-url option) and control (option:--ctrl-url option) URLs at the same time. include::common-cmd-help-options.txt[] include::common-cmd-footer.txt[] SEE ALSO -------- linklttng:lttng-destroy(1), linklttng:lttng-set-session(1), linklttng:lttng(1)