Why my disk and CPU are busy without me
Written by David Alison · July 4, 2008
I’m off at the beach this weekend with the family so I brought the trusty MacBook along. Overnight I closed the lid, putting the MacBook to sleep, and not long after I opened it this morning iStat menu was showing a lot of CPU activity and I could hear the disk thrashing a bit. I wasn’t running anything other than Safari at the time so I became curious; what was causing the machine to work all of a sudden?
When I looked at iStat it was showing that the find process was using 75% of my CPU activity. But what was find and why was it working now?
After a little research I found that according to Apple’s site find is a file system maintenance utility and that it is run as part of a daily, weekly and monthly schedule. Since I had put the MacBook into sleep mode overnight and the daily and weekly scheduled tasks had not run OS X decided to run it not long after I took it out of sleep mode. Normally these maintenance tasks are scheduled to run at 03:15 everyday, 04:30 on Saturdays, and 05:30 on the first day of each month.
All told it ran for about 15 minutes or so with varying periods of activity. I also found that I could see what was inside these tasks by examining the results of the daily, weekly and monthly logs. If you want to see what your Mac has been up to while you were sleeping just pop open one of the following files:
/var/log/daily.out
/var/log/weekly.out
/var/log/monthly.out
Inside of these files are the details of what the scheduled maintenance tasks were up to.
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