I've been going through all of my stuff lately changing passwords. I like to do that periodically for security reasons. One of the things I needed to change recently was the Luks password on my Linux desktop which is running Xubuntu Linux.
There is an easy to use GUI for Gnome that you can use to do this. Just run the following from the terminal to install it:
sudo apt-get install gnome-disk-utilityOnce installed you can find it listed as "Disks" in your Settings manager:
Once open you can find the Luks portion of your drive. Select it and from the drop down menu you can select to change your password:
Next just enter your old password, then enter your new password in twice and click Change: