Changing the LUKS password can be done in several ways, through the system terminal or also from the Disk utility (gnome-disk-utility package).

Method 1: Terminal

The first thing is to know on which partition we have to act, because it can happen that we have several encrypted partitions and even with different passwords.

$ sudo cat /etc/crypttab

This file is the database of encrypted volumes, and in our case, we only have one partition.

To identify which partition of the disk is the one that shows us, we will look at the UUID and compare in another terminal with the  blkid command, which is the one that matches.

In our test it would be the partition /dev/nvme0n1p2

Next, we run the command that changes the password on the correct partition.

$ sudo cryptsetup luksChangeKey /dev/nvme0n1p2

Enter first the current password and then the new one.

Restart the system and check that the change has been made correctly.

Method 2: Disks (gnome-disk-utility)

This method can be useful for users who do not have much experience with the terminal and want to follow the steps graphically.

The first thing to do is to check if you have the Disks installed on your system. If you don't have it installed, you can do it with the following command.

$ sudo apt install gnome-disk-utility

Once inside, we place ourselves on the disk where we have the encrypted partition and look for the correct one.

Click on the settings circle and select Change Passphrase.

Type a new passphrase and click on the Change button.

Restart the system and check that the change has been made correctly.