Duplicated UUID’s can be a big problem on your machine. But luckily it is easy to change the UUID of a Linux partition and can be done in roughly 1-2 minutes!

The UUID of a Linux partition is the Universally Unique IDentifier of that partition. I would say with a fair bit of confidence that in this and most scenarios, the Linux partition UUID has more of a local machine scope.

This ID is used in a few places to identify the partition. The most notable being your /etc/fstab file, which manages the mounting of partitions at boot time. Here is a little snippet from mine…

# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    nodev,noexec,nosuid 0       0
# / was on /dev/sdc3 during installation
UUID=9467f4de-4231-401f-bcaa-fee718d49e85 /               ext4    errors=remount-ro 0       1
# swap was on /dev/sdb1 during installation
UUID=aabe7e48-2d11-421f-8609-7ea9d75e7f9b none            swap    sw              0       0

Why would you need to change a partition UUID?

The main reason being a clash of ID’s. Technically the likelihood of creating 2 identical UUID’s is very rare (read more on the Random UUID probability of duplicates). But there may be cases where you clone a partition using DD or Clonezilla and the clone resides on the same machine – different physical hard drive or partition.

Cloning using both the tools mentioned above will create an exact copy of the partition all the way down to the UUID – and now you have 2 partitions with the same UUID. From the example of my /etc/fstab above, the UUID is no longer unique and it will mount the first partition it finds with that UUID.

How do I change the UUID?

This isn’t hard at all.

First find the device path

You can find the device path using the following command:

sudo blkid

Your output will look something like this:

sudo blkid
/dev/sdb1: UUID="aabe7e48-2d11-421f-8609-7ea9d75e7f9b" TYPE="swap" 
/dev/sdc1: UUID="9467f4de-4231-401f-bcaa-fee718d49e85" TYPE="ext4" 
/dev/sdc3: UUID="93a54a4a-e0f5-4152-ae59-2245e8d16ee4" TYPE="ext4"
/dev/sde5: UUID="9467f4de-4231-401f-bcaa-fee718d49e85" TYPE="ext4" 
/dev/sde6: LABEL="var" UUID="30433f28-1b79-4b4d-9985-fef5b1c886b5" TYPE="ext4"

Here you can see that /dev/sdc1 and /dev/sde5 have the same UUID. The path of the partition I want to change is /dev/sde5

Secondly, generate a UUID

This is simple, the following command will output a UUID like below:

uuidgen
f0acce91-a416-474c-8a8c-43f3ed3768f9

Finally apply the new UUID to the partition

This is also another command, tune2fs, which will apply our new UUID to our device path:

sudo tune2fs /dev/sde5 -U f0acce91-a416-474c-8a8c-43f3ed3768f9

Done, now you can update your grub to include the correct UUID’s to reduce any risk of your system confusing the partitions.