Grub 2 and moved sytem (rant and question)

Rashkae ubuntu at
Thu Nov 18 19:32:55 UTC 2010

On 10-11-18 01:11 PM, Thierry de Coulon wrote:
> I've done it as I usually do, by copying the installation from one partition
> to another, in this case / went from sda6 to sda1 and /home from sda7 to sda2
> (using cp -r -v --preserve --no-dereference). No problem.
> I then edited /etc/fstab on the new root. Normaly, I would have
> edited /boot/grub/menu.lst but... we now have grub 2.
> First try: no luck. Grub fails with: Alert! /dev/disk/by-uuid/<some long and
> impossible to understand stuipd uuid>
This error cofuses, me since it's not really a grub error.  (grub 
doesn't have concept of /dev filesystem)  I'm guessing that grub 
succesfully loaded a kernel and initrd, but something must have gone 
wrong with the arguments that were given to that kernel.

> ************Rant 1****************************
> they say they must use uuid's because "if partition order changes one can not
> boot anymore". Well, when does partition order change without the user doing
> it? And it's easy to correct with /dev/sdx, not with uuid! And if you clone
> your disk _nothing_ works at all because _all_ uuid's change! Great! Now even
> when the partition order did not change you can't boot anymore...
> **********************************************
The /dev/sdx is very easy to change through no direct action from the 
user on systems with multiple hard drives, multiple i/o cotrollers. It 
was becoming a real problem.
> Now, luckily, I could still boot my old installation and search for
> information as to how get grub 2 to find out about the new uuid if my root
> partition, but I found none! update-grub did not do it. Grub 2 documentation
> is as easy to read as the darkest night and they should really have created
> tools to manage it before they use it as default boot loader.
  How exactly were you booting to your old installation?  update-grub 
should have been all you needed to run to make this work.  For 
troubleshooting something that went wrong, I would need the output of 
sudo blkid, the contents of your new fstab, as well the contents of 
/boot/grub/grub.cfg file after running update-grub.

Note: once booted to your new partition, you would also want to run 
grub-install, otherewise grub will still be loading it's own files from 
the old boot partition.

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