Daemons

[Susan Dridi-2]

I'm curious about some daemons that are running. Do I need the icecast
server or the portmap daemon for anything? I noticed those two in the
boot messages, not sure what other daemons are running or if I need them.

I'm trying to figure out what is accessing my hard drive a couple of
times a second. The blue light in the front of my computer is constantly
flashing, even when I'm not doing anything and don't have any
applications open.

Thanks!

-Susan

P.S. - Daniel, can't wait to get your book!

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[Gustin Johnson]

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Susan Dridi wrote:
> I'm curious about some daemons that are running. Do I need the icecast
> server or the portmap daemon for anything? I noticed those two in the
> boot messages, not sure what other daemons are running or if I need them.
>
> I'm trying to figure out what is accessing my hard drive a couple of
> times a second. The blue light in the front of my computer is constantly
> flashing, even when I'm not doing anything and don't have any
> applications open.
>
Icecast is for broadcasting mp3s and the like accross the net, so it
does not need to be running all the time.  Portmap is used by a number
of things (anything that makes use of RPC), most notably NFS and should
not really be a problem.  It should still be safe to run
"/etc/init.d/portmap stop" to see if that helps.

For tracking down disk I/O usage, I start with iostat:
For a better formated version:
http://pastebin.com/f4625c32e

iostat -x
Linux 2.6.24-19-generic (midwinter)     17/01/09

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          17.55    5.18   14.45    1.03    0.00   61.79

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s
avgrq-sz avgqu-sz   await  svctm  %util
sda               0.09     0.08    0.01    0.00     1.27     0.69
140.81     0.00   18.12   8.36   0.01
sdb               0.01     8.93    0.21    2.73     1.81    93.26
32.39     0.02    5.22   0.45   0.13
sdc               0.48    24.34    1.74    6.30    29.84   245.33
34.21     0.35   43.61   1.60   1.29
sdd               0.09     0.06    1.46    0.68   333.57   190.40
244.28     0.06   27.14   3.10   0.66
sde               0.05     1.11    4.01    5.09    75.26   304.43
41.69     0.02    2.15  12.50  11.38
dm-0              0.00     0.00    1.55    0.74   333.57   190.40
228.56     0.09   37.15   2.90   0.67
sr0               0.00     0.00    0.00    0.00     0.00     0.00
11.69     0.00   51.08  49.54   0.00

You could always use sar -d but you have to make sure that
/etc/default/sysstat has the "enabled" option set to true.  You can then
start and stop monitoring with "/etc/init.d/sysstat start".  Sar -d will
give you the partition so I usually use it.  I also usually stop
performance monitoring while doing low latency work.  I have not tested
the overhead in a while but back when I had a PIII/AMD Thunderbird, it
did make a difference.

- From here I can see which block device (hard drive) is busy.  So now I
am going to try and track down which process(es) are responsible.

If you use sar -d you have the major and minor number for the disk in
question, otherwise you need to find it:
ls -l /dev/sda*
brw-rw---- 1 root disk 8, 1 2008-10-07 17:48 /dev/sda1

lsof | grep "8,1" | awk '{print $1" "$2}' | uniq -c | sort -n -r
7 vmware-vm 15491
1 bash 8188
1 bash 8137

So in my case vmware has 7 files open, and is the likely candidate.

You can also look at htop and atop.  htop is pretty good for looking
through your system and it can be resorted on the fly.

I would also get to know lsof, probably one of the least known and yet
most useful utilities ever made.  Second only to screen IMO.

You can get more info on lsof here:
http://dmiessler.com/study/lsof/

I originally got that long lsof command line from a web site.  I can't
remember which one, but a google for disk IO linux should find it (or
one like it).

Hth,
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[Gabriel M. Beddingfield]

On Fri, January 16, 2009 3:26 am, Susan Dridi wrote:
> I'm curious about some daemons that are running. Do I need the icecast
> server or the portmap daemon for anything? I noticed those two in the
> boot messages, not sure what other daemons are running or if I need them.
>
> I'm trying to figure out what is accessing my hard drive a couple of
> times a second. The blue light in the front of my computer is constantly
> flashing, even when I'm not doing anything and don't have any
> applications open.

Have you checked your logs?  /var/log/syslog, 'dmesg', /var/log/auth, etc.

Ofen, when I see this happen it's because there's an error of some sort
that is spamming the logs.  I've seen it a lot with CD-ROM drives when
there's a bad disk... or when KsCD is trying to access an audio disk (but
there's a data disk in the tray).  I would see errors like "I/O read error
on /dev/hdc at sector 23456."

HTH,
Gabriel

--
               G a b r i e l   M   B e d d i n g f i e l d

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