LTTng » LTTng-tools

Consider:

$ lttng create silly
Session silly created.
Traces will be written in /home/username/lttng-traces/silly-20130920-144709
$ lttng disable-event -u -a
Error: UST channel not found
$ lttng list silly
Tracing session silly: [inactive]
    Trace path: /home/username/lttng-traces/silly-20130920-144709

=== Domain: UST global ===

Buffer type: per UID

Error: UST channel not found

The domain has been created but not the default channel. This contrasts with the lttng enable-event -u -a command (also issued just after session creation), which creates the domain and the default channel channel0 with the event "*":

$ lttng create silly
Session silly created.
Traces will be written in /home/username/lttng-traces/silly-20130920-144709
$ lttng enable-event -u -a
All UST events are enabled in channel channel0
$ lttng list silly
Tracing session silly: [inactive]
    Trace path: /home/username/lttng-traces/silly-20130920-144709

=== Domain: UST global ===

Buffer type: per UID

Channels:
-------------
- channel0: [enabled]

    Attributes:
      overwrite mode: 0
      subbufers size: 131072
      number of subbufers: 4
      switch timer interval: 0
      read timer interval: 0
      output: mmap()

    Events:
      * (type: tracepoint) [enabled]

Clearly, disable-event -u -a should, when the session is virgin, create the domain, a channel0 default channel, and an event filter "*" (toggled to disabled). This would achieve symmetry with enable-event.