Thursday June 21, 2007 Dan Mick's Little Shop of Hints
Thursday June 21, 2007 Ever had your system constantly transmitting network packets, and had a hard time finding out who or why?
Recently my system was sending loads and loads of DNS requests for a system I knew not to be on the network (an old system of mine that had been decommissioned). I saw the DNS requests with snoop(1m), but had no idea which process was doing the job.
Enter dtrace. 15 seconds of experimentation: first, look to see if there are functions being called with "udp" in their name:
dtrace -n 'fbt::*udp*:entry'
Yes, there certainly are. OK, modify the above to suppress the default print with -q, and add what I'm interested in, straight out of built-in variables:
dtrace -q -n 'fbt::*udp*:entry{printf("%s from %s(%d)\n", probefunc, execname, pid);}'
(Turns out it was automountd. A quick service disable/enable, and it stopped.) Another mysterious system behavior immediately found with dtrace. ( Jun 21 2007, 02:30:30 PM PDT ) Permalink
