lttng-create(1) =============== :revdate: 18 January 2018 NAME ---- lttng-create - Create an LTTng tracing session SYNOPSIS -------- Local mode: [verse] *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='PATH'] [option:--no-output | option:--output='PATH' | option:--set-url=file://'PATH'] Network streaming mode: [verse] *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] [option:--shm-path='PATH'] (option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL') Snapshot mode: [verse] *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] option:--snapshot [option:--shm-path='PATH'] [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL'] Live mode: [verse] *lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *create* ['SESSION'] option:--live[='DELAYUS'] [option:--shm-path='PATH'] [option:--set-url='URL' | option:--ctrl-url='URL' option:--data-url='URL'] 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 man: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 man:lttng-crash(1) utility. Tracing sessions are destroyed using the man:lttng-destroy(1) command. Creation modes ~~~~~~~~~~~~~~ There are four tracing session modes: [[local-mode]]Local mode:: Traces the local system and writes the trace to the local file system. The option:--output option specifies the trace path. Using option:--set-url=file://'PATH' is the equivalent of using option:--output='PATH'. The file system output can be disabled using the option:--no-output option. + If none of the options mentioned above are used, then the trace is written locally in the `$LTTNG_HOME/lttng-traces` directory (`$LTTNG_HOME` defaults to `$HOME`). [[network-streaming-mode]]Network streaming mode:: Traces the local system and sends the trace over the network to a listening relay daemon (see man:lttng-relayd(8)). The option:--set-url, or option:--ctrl-url and option:--data-url options set the trace output destination (see the <> section below). [[snapshot-mode]]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 man:lttng-enable-channel(1)). The man: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]]Live mode:: Traces the local system, sending trace data to an LTTng relay daemon over the network (see man: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 the <> section below). [[url-format]] URL format ~~~~~~~~~~ The option:--set-url, option:--ctrl-url, and option:--data-url options' arguments are 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* and can only be used as the option:--set-url option's argument when the session is created in <> or <> mode. 'TRACEPATH':: Absolute path to trace files on the local file system. The other version is available when the session is created in <>, <>, or <> mode. 'NETPROTO':: Network protocol, amongst: + -- `net`:: TCP over IPv4; the default values of 'CTRLPORT' and 'DATAPORT' are respectively {default_network_control_port} and {default_network_data_port}. `net6`:: TCP over IPv6: same default ports as the `net` protocol. `tcp`:: Same as the `net` protocol; can only be used with the option:--ctrl-url and option:--data-url options together. `tcp6`:: Same as the `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 man:lttng-relayd(8). include::common-cmd-options-head.txt[] Mode selection ~~~~~~~~~~~~~~ option:--live[='DELAYUS']:: Create the session in <>. + 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 man:lttng-relayd(8)). + By default, 'DELAYUS' is {default_lttng_live_timer} and the network URL is set to `net://127.0.0.1`. option:--snapshot:: Create the session in <>. 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:: In <>, do not output any trace data. option:-o 'PATH', option:--output='PATH':: In <>, 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 'URL', option:--ctrl-url='URL':: Set control path URL to 'URL' (must use option:--data-url option also). option:-D 'URL', option:--data-url='URL':: Set data path URL to 'URL' (must use option:--ctrl-url option also). option:-U 'URL', 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. + In <> mode, 'URL' must start with `file://` followed by the destination path on the local file system. include::common-cmd-help-options.txt[] include::common-cmd-footer.txt[] SEE ALSO -------- man:lttng-destroy(1), man:lttng-set-session(1), man:lttng(1)