Unix-like operating systems decouple the user name from the user identity, so you may safely change the name without affecting the ID. All permissions, files, etc are tied to your identity (uid), not your username.
To manage every aspect of the user database, you use the
To change username and user's groupname (it is probably best to do this without being logged in):
sudo usermod -l newUsername oldUsername
sudo groupmod -n newUsername oldUsername
This however, doesn't rename the home folder.
To change home-folder, use
sudo usermod -d /home/newHomeDir -m newUsername
after you changed the username.
For instance, you could logout, drop to a console (Ctrl+Alt+F1), and
sudo su - to become true root (as opposed to
sudo -s, where $HOME is still /home/yourname.) Maybe you also have to kill some still running processes from this user first. To do so, enter
ps -u username, look for the matching PID and kill them by
Update: as arrange mentioned, some files may reference your old home directory. You can either keep a symlink for backward compatibility, e g
ln -s /home/newname /home/oldname or you can change the file contents with
sed -i.bak 's/*oldname*/*newname*/g' *list of files* It creates a backup for each file with a .bak extension.
Some additional information for not so experienced users like me:
As I only have ONE user account (administrator), it would not let me change the username ("you are already logged in" was the response in TTY1 (Ctrl+Alt+F1). To get around this:
Login with your old credentials and add a new user, e.g. "temporary" in TTY1:
sudo adduser temporary
set the password.
2. Allow the temporary user to run sudo by adding the user to sudo group:
sudo adduser temporary sudo
Log out with the command
Return to tty1: Login with the 'temporary' user account and password. Change your username and folder as mentioned above.
exit (until you get the login prompt)
Go back to TTY7 (Ctrl+Alt+F7) to login on the GUI/normal desktop screen and see if this works.
Delete temporary user and folder:
sudo deluser temporary
sudo rm -r /home/temporary