"I'm sorry, Dave, but I can't let you have your disk back" (Shallow Thoughts)

Akkana's Musings on Open Source, Science, and Nature.

Sat, 30 Jul 2005

"I'm sorry, Dave, but I can't let you have your disk back"

I got a new, large, and most important, quiet disk for my laptop.

The first Linux distro I installed on it was Ubuntu. Since quiet was my biggest incentive for buying this disk (the old IBM disk was so loud that I was embarassed to run the laptop in meetings), as soon as the install was finished I carried the laptop into a quiet room to listen to the disk,

Turns out it was making a faint beep-beep noise every second or two, plus some clicking in between.

Another, non-Linux, operating system installed on the same disk does not make these beeping or clicking noises. It was clearly something Ubuntu was doing.

After a long series of ps and kill, I finally narrowed the problem down to hald. HAL is polling my disk, once per second or so, in a way that makes it beep and click.

(HAL, if you're not familiar with it, is the Hardware Access Layer which works hand in hand with the kernel service udev to monitor hardware as it comes and goes. No one seems to know where the dividing line is between udev and hal, or between the daemons udevd and hald. Most systems which enable one, enable both.)

I floated down to the control room to dismantle HAL, humming "Daisy".

But it turned out I didn't need to kill HAL entirely. The polling apparently comes from HAL's attempt to query the CDROM to see if anything has been inserted. (Even if there is no CDROM connected to the machine. Go figure!)

The solution is to edit /etc/hal/hald.conf, and change true to false under <storage_media_check_enabled> and <storage_automount_enabled_hint>. This changes hald from a "blacklist" policy, where everything is polled unless you blacklist it, to a "whitelist" policy, where nothing is polled unless you whitelist it. Voila! No more polling the disk, and no more beepy-clicky noises. I suspect my drive will last longer and eat less battery power, too.

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[ 19:00 Jul 30, 2005    More linux | permalink to this entry ]