Change username for a Linux user

This is how I change my login username for my Linux (Debian) machine.

First I log out to make sure no processes are running for that user, then I log in as root.

Then make sure no processes are still running as the olduser

ps aux | grep olduser

kill any process still running as olduser before continue, renaming a user will fail if a process is still running.

Lets change the login name of the olduser account to the new raddinox login name

usermod -l raddinox olduser

and to change the olduser group to raddinox

groupmod -n raddinox olduser

Now it is possible to login and use my new raddinox user, but the home folder is still /home/olduser so to change that we need to rename the folder and change the home folder path for the user

First we change the user home folder path

usermod -d /home/raddinox raddinox

Now my new user has the /home/raddinox path just like I want to, but this path does not exist. I want all my old settings so lets just rename our old home folder to the new one

mv /home/olduser /home/raddinox

Finally done and I can now use my new raddinox user.