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02 November 2005

Checking System Activity on Mac OS X on the Command Line

Logging into server, no GUI, see?
 

So I'm logging into a Mac OS X machine (Server or not) remotely by ssh to do some maintenance and check on the health of the system. What I might be interested in is how CPU, memory and disk usage is coping with the jobs the server has to do. If I was sitting in front of the machine I could open "Activity Monitor" and click my way through the GUI. Not an option for this machine, since there is no GUI level remote access. So what do I do? There are some command line tools to give me the information I need, let me show you top, vm_stat and iostat...


On my OpenBSD box "systat vmstat" is what I use for a full overview. That is not available for OS X, but some other tools are there. Most often used is "top", followed by "vm_stat" and "iostat".

top

"top" is well known and you likely have heard about it and probably used it before. The version on OS X is quite useable. After switching to "compatibility mode" (with 'x'), one can see only the processes of a single user (with 'U' and entering the user id or name). Top is good for checking what eats all the CPU time.

vm_stat

If it comes to memory usage, especially for the question "how much swap space am I using", then vm_stat can help. On Mac OS X that's vm_stat with an underscore, not vmstat. You just give vm_stat a delay in seconds (by calling it like "vm_stat 10" on the command line) and it updates the display repeatedly. Go on, try that out and then open a bunch of applications to see if pageouts are going up (which would mean that your machine has to page memory out on disk to make room for the new ones).

$ vm_stat 5
Mach Virtual Memory Statistics: (page size of 4096 bytes, cache hits 58%)
  free active inac wire   faults     copy zerofill reactive  pageins pageout
 49314  97619 154001 26746 42361341   320895 24148787   145786    50308 3459
 49341  97814 153974 26551     2902       21     1429        0        0 0
 45297  98409 157246 26728    12056      805     5639        0      272 0
 40400 101288 158727 27265    14663      841     6746        0     1261 0
 36365 103524 160004 27787     8302      712     3519        0     1630 0
...looks like my workstation is OK, even with starting up Acrobat Reader and a bunch of smaller programs at once.

iostat

It took me longer to discover iostat. The man page says that "Iostat displays kernel I/O statistics on terminal, device and cpu operations." Which is quite a lot and probably more than I usually want. I just use it with a line like:

iostat -d -K -w 5
to show me only devices (-d), kilobytes instead of blocks (-K), and have a wait interval of 5 seconds (-w 5). Go ahead, try it and watch it while doing a find for "foobar" on your disks. As usual with all command line tools, read the fine man pages.
$ iostat -d -K -w 5
          disk0
  KB/t tps  MB/s
 16.90   1  0.01
 31.79 131  4.07
 32.00 752 23.51
 32.00  35  1.10
  4.00   1  0.00
  0.00   0  0.00
^C
Finding all files that start with "pimp" on my single disk got the activity up a bit, then I stopped it with control-C. The display shows me Kilobytes per transfer, transfers per second, and Megabytes per second. Interpretation is of course up to you not to the tool :-). Playing with the -I switch might be interesting.

Posted by betabug at 13:20 | Comments (0) | Trackbacks (0)
ch athens
Life in Athens (Greece) for a foreigner from the other side of the mountains. And with an interest in digital life and the feeling of change in a big city. Multilingual English - German - Greek.
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