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I have a fedora guest OS in VMware. I want to expand /boot partition, so I add another virtual disk to this VM, and try to clone the disk.

After dd if=/dev/sda1 of=/dev/sdb1, blkid report that /dev/sda1 and /dev/sdb1 have same UUID/GUID.

It's weird that there're 2 same UUIDs in the universe, how to change one of them to another UUID value?

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It's not weird at all. When you clone a partition with dd, of course the clone will have the same UUID as the original. The UUID is just metadata of the partition - not some inherent property of a physical disk. – Andrew Medico May 4 '11 at 3:08
Thank you Andrew, I thought UUID is a calculated value before when a new partition been created. Now I know it's just a metadata stuff. – LiuYan 刘研 May 4 '11 at 3:32
Thanks Andy, now I got a new UUID on /dev/sdb1 – LiuYan 刘研 May 4 '11 at 3:53

migrated from stackoverflow.com May 9 '11 at 2:18

2 Answers

up vote 6 down vote accepted

Assuming it is an ext2-family filesystem:

uuidgen
tune2fs -U <output of uuidgen> /dev/sdb1

Or if you're confident uuidgen is going to work:

tune2fs -U `uuidgen` /dev/sdb1

The UUID is stored in the superblock, so a byte-for-byte copy of the filesystem will have the same UUID.

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Thanks Andy, now I got a new UUID on /dev/sdb1 – LiuYan 刘研 May 4 '11 at 3:53
4  
Andy, you don't even need uuidgen command: "tune2fs -U random /dev/sdb1" should work fine – grzuy Mar 21 '12 at 2:58
up vote 2 down vote

For XFS, use: xfs_admin -U <uuid> <device>

Use xfs_admin -u <device> to view a UUID (note lower case option to view, versus upper case option to set). Another post on U&L pointed out the blkid command for viewing all or some of the UUIDs on the system.

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