Does it relate to UUIDs? (because blkid shows that both partitions have the same UUID)
Yes. If your intent is to create an independent OS, you need to assign a different UUID. GParted can do that for you. Right-click on the cloned partition, and choose
new UUID. A random UUID will be assigned to the partition.
How can I "separate" the two Ubuntus from each other? Make them 2 independent OSs.
- It's been a while since I did this. I remember having to change /etc/fstab and /boot/grub/grub.cfg of the cloned partition to reflect the new UUID. Be careful with grub.cfg coz there are multiple entries of the old UUID that needs to be edited. Make sure to get them all.
- Boot into the original partition, make sure the cloned partition is no longer being mounted upon boot, and do
sudo update-grub to create the new menu entries for the cloned partition.
- Reboot into the cloned partition to check if it works. I may have missed out on other entries that needs to be changed.
Is this a good idea?
If your intent is to make a back-up, then NO. There are better ways to back up your root partition without resorting to cloning and changing UUIDs.
If the intent is to make a separate, independent OS out of the original root partition, then maybe yes.