I installed Fedora Core 5 on a system which I want to use as a MythTV frontend, and to that end I want to have the harddisk power down automatically when it is not used to make the box as quiet as possible. However, Fedora is not letting me do it!

Some process is apparently continually accessing the harddrive (I can see the harddisk light flicker every couple of seconds or so, very regularly). If I set the powerdown timeout to one minute with hddparm -S 12 /dev/hda it never powers down, and if I power it down manually with hddparm -y /dev/hda it starts back up only a few seconds later every time.

Can anyone here tell me how I can find out which process is doing this? Or does someone already happen to know what Fedora Core 5 has running in the background which could cause this? I don't think it's the system log, because /var/log/messages will usually only have entries in it from at least several minutes earlier.

I hope someone can help me out! Many thanks in advance for any light you can shed...

Kind regards,
Pepijn Schmitz

You wouldn't happen to have used a journaling file system by any chance? You can use top to see if you can catch it that way.

Fedora Core seems to have chosen ext3 as the default file system, which is a journaling file system I believe. But does that mean that it continually writes to the harddisk, even when no processes are actually writing to the filesystem?

I tried running top, but I didn't see anything special happen at the moments the harddrive light flickers...

If you want no drive activity at all, you may want to try ext2 which has no journal if I recall correctly. For your situation you may want to look at how people put laptops to sleep. That is essentially what you are doing.

Sometimes top will catch it if you are lucky. Updating the journal is very fast so it just may not catch it.

Hope that helps a bit.

Have a look at your cron files, too. Some applications are said to automatically add entries there.

I thought of another one that may not apply. Make sure if you use KDE that you don't have a slideshow for your desktop that changes pretty often.

@ dalek Umm, I just came to think of it: there should not be any necessity to write to a journal in a regular way, after all there is no obvious activity by the OP. Furthermore the system has buffers and once they are sync-ed... Or am I missing something entirely here?

Well, I have reiserfs on all my partitions and I see in gkrellm where it reads and writes pretty regular just to keep the journal up to date I assume. The writes are small but that is all it needs to keep the drive spinning. I'm no expert on the journals though. I just notice it doing it a lot.

Well, from their website: "About: GKrellM is a GTK-based stacked monitor program that charts SMP CPUs, disks, load, active net interfaces, and internet connections. ..." Might be gkrellm itself?