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I did a kernel upgrade on my desktop system from 2.6.32-41 to 2.6.32-42 using apt-get dist-upgrade. I opted not to update /boot/grub/menu.lst and added the required lines myself, based on the previous version. (As I found from previous experience that the automatic update trashes the existing entires!) So the relevant lines for non-recovery mode read:

title    Ubuntu 10.04.4 LTS, kernel 2.6.32-42-generic
uuid     099b8ec7-c3b2-4f46-a52c-8e95d6a7b9de
kernel   /vmlinuz-2.6.32-42-generic root=/dev/smallvg-filesystemlv ro quiet splash
initrd   /initrd.img-2.6.32-42-generic

title    Ubuntu 10.04.4 LTS, kernel 2.6.32-41-generic
uuid     099b8ec7-c3b2-4f46-a52c-8e95d6a7b9de
kernel   /vmlinuz-2.6.32-41-generic root=/dev/mapper/smallvg-filesystemlv ro quiet splash 
initrd   /initrd.img-2.6.32-41-generic

2.6.32-41 boots normally; 2.6.32-42 fails because it can't find the root partition, as the logical volume isn't mounted. It drops me into busybox, from which (as suggested in answers to previous similar problems) I can use

lvm -vgscan


lvm vgchange -ay

to verify that lvm is present and the partitions are visible to it.

I have examined and compared the 2 /boot/initrd.img* files, and as far as I can tell the contained files and their contents are the same (apart from the version changes), and checked the 2 /boot/config* files, which again only differ by version numbers.

This seems to be a similar problem to this one, which doesn't yet appear to have been resolved, although baronKarza doesn't specify the kernel numbers involved.

So I am at a loss to work out where it is broken. Has anyone else experienced this? Can anyone help, please?

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up vote 1 down vote accepted

There is a typo in the kernel line for the new entry; it should be:

kernel   /vmlinuz-2.6.32-42-generic root=/dev/mapper/smallvg-filesystemlv ro quiet splash

You have omitted the bolded mapper part!

share|improve this answer
You're right. And that's what I had originally when it wouldn't boot. But, as there were no filesystems visible under /dev/mapper in busybox, I also tried it without mapper/, and that was the version I posted. I have now reinstated mapper/ and it boots OK, so I have no idea what was wrong on the first attempt. Thanks for your quick reply, izx. A fresh pair of eyes often helps solve a problem! – peterm Aug 18 '12 at 14:13
Thanks. I'm new to Ask Ubuntu, and I was wondering how to mark the question as answered. – peterm Aug 18 '12 at 16:44

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