Booting from cd, how update grub2 to reflect changed uuid?

Question

I changed disks around now I get a message from grub (grub2) saying disk w/ uuid=XXXX does not exist.

I've booted from a usb flash drive now, but can't figure out how to run the grub update so that it targets the right grub installation. I gather it would just update the one associated with the current booted system. What am I missing?

To add to my confusion, the install I wish to recover is on an encrypted lvm volume, though the boot partition is not in lvm nor encrypted, but it makes it harder to just go around and reinstall. I do have a backup of the luks header if need be, hope to just get back to old install though.

Thank you!

Answer 1

Couple of steps to fix this:

• Use sudo fdisk -l to get a list of the current partitions. Output will be of the form:

  Device Boot      Start         End      Blocks   Id  System
  /dev/sda1   *        2048      391167      194560   83  Linux
  /dev/sda2          391168    40429567    20019200   83  Linux
  /dev/sda3        40431614    41940991      754689    5  Extended
  /dev/sda5        40431616    41940991      754688   82  Linux swap / Solaris
  

• Use sudo blkid device to get the UUID for your boot partition. Suppose it's sda1, then sudo blkid /dev/sda1 would give something like:

  /dev/sda1: UUID="b3855dc7-ab6e-4167-92a8-7679477e17c2" TYPE="ext3" 
  

• Edit your /etc/fstab to reflect the new UUID: