How do I permanently reset the UUID of an LVM partition?

Question

A (dd cloned) backup of my boot partition left me with duplicate UUIDs.

blkid shows:

/dev/sda1: UUID="32579810-0388-416d-bb49-7031ac2c2975" TYPE="ext4"
...
/dev/mapper/raidgroup-osbackup: UUID="32579810-0388-416d-bb49-7031ac2c2975" TYPE="ext4"
...

where /dev/mapper/raidgroup-osbackup is an LVM device.

I booted from a live Ubuntu image and tried:

sudo tune2fs -U random /dev/mapper/raidgroup-osbackup

This appeared to succeed and the target device showed a new UUID.

However, after reboot /dev/mapper/raidgroup-osbackup was remounted at / and blkid showed the original UUID.

I thought the change with tune2fs was supposed to be permanent, but this does not seem to be the case. How can I fix this?

Solution

I seem to have solved it now. I am not sure exactly which step solved the problem, but this time I did:

Generate new UUID:

uuidgen

This gave me a new UUID which I then copied into:

sudo tune2fs -U <insert here> /dev/mapper/raidgroup-osbackup

I then disabled the logical volume /dev/mapper/raidgroup-osbackup using:

sudo lvm lvchange -an /dev/mapper/raidgroup-osbackup

I disabled the other logical volumes on the same volume group and physical volume. I then disabled the underlying (software) RAID array in the "Disks" GUI. I re-enabled the RAID array in "Disks" which in turn automatically re-activated the logical volume whos file system I was messing with. Checking the UUID with blkid, I could now confirm that the UUID was still changed.

Just as an extra confirmation, I rebooted the Ubuntu live image and once again checked the UUID of /dev/mapper/raidgroup-osbackup with blkid. Still changed - so this part is solved now.

Along came a new problem... When rebooting the system from the ordinary install, the boot loader somehow still gets the wrong partition mounted at / despite the fact that the UUID is now different. I have posted this problem as a new question: Why does Ubuntu mount the wrong partition as root?

Comments

[Daniel B]

Are you perhaps cloning the entire filesystem? You might want to look into the “Skip Activation” flag for LVM.

[Thomas Arildsen]

I think the duplicate UUID indeed comes from cloning the entire file system with dd. It seems it should be easily solved by simply changing the UUID of the backed-up partition. But why does the UUID revert to its original value?

[Thomas Arildsen]

It is my impression that I should not need to modify the fstab. I want to retain the original UUID of the partition /dev/sda1 (which is the one I want to boot at /). So when this is still the UUID listed in fstab and I assign a new one to /dev/mapper/raidgroup-osbackup, I suppose I should not change the one in fstab?