[lttng-dev] beginner question

[Loris Degioanni]

I just installed the lttng package on a fresh Ubuntu 12 machine, and I'm 
following the tutorial at http://lttng.org/quickstart.
The enable-event step fails with this error:

# lttng enable-event sched_switch,sys_open -k
kernel event sched_switch created in channel channel0
Error: Event sys_open: Enable kernel event failed (channel channel0, 
session mysession)
Warning: Some command(s) went wrong

What am I doing wrong?

Loris