laptop-mode disabled in kernel?

James Gray james at
Tue Jul 11 22:48:11 UTC 2006

Hash: SHA1

marc wrote:
> James Gray said...
>> marc wrote:
>>> In Dapper, my laptop fan never turns off after the first few minutes. It 
>>> is always on. Whereas, in Windows, it rarely comes on. I'm pretty sure 
>>> that this is because the disk never spins down.
>> - -->8-- Snipped --8<--
>>> Back to the disk. There's only one active ext3 partition plus swap - all 
>>> other partitions are noauto. I've tried noatime and commit=600, but to 
>>> noavail. Any ideas?
>> ext3 is the problem with your disk.  It uses a forced-flush interval of
>> about 30 sec IIRC.  In other words, regardless of what is or isn't going
>> on, the ext3 driver forces a sync and hence the hard drive never goes to
>> sleep (neither would you if someone poked you in the ribs every 30
>> seconds!).
>> Solution, unfortunately, requires reformatting ALL the ext3 partitions
>> with something else.  I'd suggest reiserfs as, like ext3, is a
>> journaling file system and is quite mature.  I can't remember if jfs and
>> xfs use the same "fixed sync interval" fru-fru like ext3 though, so I'll
>> hold short of recommending them.
> Thanks for this. I was in two minds about going this way, but then 
> decided to jump.
> And now, I have a little problem :-o
> Here's the story, so far
> - moved Kubuntu (on sda3) to a safe place while booted on another 
> partition (sda6)
> - formatted sda3 as reiserfs
> - amended both fstabs (sda3 and sda6)
> - mounted the newly formatted partition
> - moved the data back onto sda3
> - rebooted.
> Grub currently loads from sda3, or rather it doesn't now. I'm getting an 
> error 17 : Cannot mount selected partition. I'm not overly surprised, 
> but I'm not sure what to do next.

You probably need to add the reiserfs module to the initrd.  Add the
reiserfs line to /etc/modules then rebuild the initial ram disk
(mkinitrd), then move the old one out of the way, and copy the new one
in (with the same name as the old one).  Reboot and you should be sweet.

FWIW, I usually create a 30-50MB partition in ext2 format mounted at
/boot - this avoids some problems with different boot loaders.  Maybe
those problems are historical but it's been a practise that works well
for me.

> I can mount the partition from a live CD without a problem, and I 
> obviously mounted it from my sda6 partition.

Yup - because the live CD loads the reiserfs module on demand as the
kernel is already running and has mounted the /lib.  The problem with
booting is that it needs the reiserfs module to mount "/", but the
module is on "/"...chicken and egg problem.

Initial ram disks (initrd) were invented to get around this problem.
Usually when you install Ubuntu (and any other Linux distro) the
installer adds whatever modules that are needed to mount the root file
system for you.  If you change the format of the root file system
post-installation, you need to modify the initial ram disk yourself.


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