How to change username ubuntu with command line?

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 usermod tool.

To change username (it is probably best to do this without being logged in):

sudo usermod -l 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