RQ: wisdom re kernel changing

catkin · 02-07-2009, 08:20 AM

Hello

Can those with more experience please contribute wisdom about kernel changing?

A recent system upgrade (apt-get upgrade) upgraded 106 packages. It included ubuntu 8.04.2 (was 8.04.1) and a new init image, /boot/initrd.img-2.6.24-19-generic (was same name).

The upgrade broke reading files from DVD (the backup script runs cksum on the backup files on DVD). Reading files from DVD has long been troublesome; essentially the problem is as reported at launchpad bug 228624 although the problem has been intermittent and symptoms have varied. The "all_generic_ide=1" workaround described there had given blessed relief from failed DVD reads for a couple of months until the recent upgrade.

So -- how to fix reading files from DVD? This is where my ignorance comes in and wisdom would be helpful both with the techniques and in weighing the pros and cons.

One option is to back out the recent package upgrades. Speculation puts the problem in the area of DVD file system mounting/automounting, UDMA, IDE/PATA/SATA. How about guessing the problem is kernel related and backing out the latest kernel change? How to do that? How to find documentation on doing that? Better/possible to back out all 106 changes and re-apply progressively? How to do that?

Another option given at launchpad bug 228624 is to change to the 2.6.27 kernel. A 2.6.27 kernel prepared for Hardy was used in Intrepid Alphas. How to find? How to try/backout? How to find documentation on doing that? This would be contrary to the philosophy of using a mature LTS version for stability? What is "stability" worth if the backups don't run reliably?!

Anything else to consider while managing (ha!) this problem?

Best

Charles

alan_ri · 02-09-2009, 08:06 AM

What's the output of

Code:

uname -a

Code:

ls -l /dev/cdr*

Did you tried to read files with the old kernel.There should be an option in the boot menu for it.Have you tried with

Code:

all_generic_dma=1

catkin · 02-09-2009, 01:42 PM

Thanks Alan

uname -a
Linux CW8 2.6.24-19-generic #1 SMP Wed Aug 20 22:56:21 UTC 2008 i686 GNU/Linux

ls -l /dev/cdr*
lrwxrwxrwx 1 root root 4 2009-02-09 18:06 /dev/cdrom1 -> scd0
lrwxrwxrwx 1 root root 4 2009-02-09 18:06 /dev/cdrw1 -> scd0

The old kernel is not in /boot/grub/menu.lst because it's not a full kernel, just a new initrd.img file. The only reason I know it was changed by the recent upgrade is the presence of a new initrd.img-2.6.24-19-generic file:

ls -lrt /boot/initrd*
-rw-r--r-- 1 root root 7.4M 2008-06-16 21:52 /boot/initrd.img-2.6.24-16-generic.bak
-rw-r--r-- 1 root root 7.7M 2008-06-16 22:15 /boot/initrd.img-2.6.24-16-generic
-rw-r--r-- 1 root root 7.8M 2008-12-08 21:25 /boot/initrd.img-2.6.24-19-generic.bak
-rw-r--r-- 1 root root 7.8M 2009-02-05 01:31 /boot/initrd.img-2.6.24-19-generic

The problem has "gone away" for the last 5 backups. It's been intermittent since it began so that's nothing special. When it comes back I'll try all_generic_dma=1

Best

Charles

alan_ri · 02-09-2009, 02:01 PM

OK, if you'll need to fix it again then you could try with this;

Code:

sudo chown username:username /media/cd*
sudo chmod 777 /media/cd*
sudo chown username:username /dev/cd*
sudo chmod 777 /dev/cd*
sudo chown username:username /dev/scd0
sudo chmod 777 /dev/scd0

You can do it now also.As a user you'll have better permissions and you'll be the owner.

catkin · 02-09-2009, 02:09 PM

Thanks again, Alan

I'll give the permissions a try but I'm not hopeful -- the backup is run as root and if it was a permissions problem wouldn't it be solid, not intermittent?

Best

Charles