How to safely change username and hostname?

Question

I installed a fresh Ubuntu Gnome 14.04.3 today, but I just notice that I reversed the username and hostname during installation.

To illustrate this, when I open a terminal, the prompt looks like :

myhost@myname:~$

instead of

myname@myhost:~$

It is the unique user (so it is the normal admin).

How can I fix this problem ?

Answer 1

To change the hostname

You need to edit the computer name in two files as root user:

/etc/hostname 

and

/etc/hosts

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

usermod -l newUsername oldUsername

This however, doesn't rename the home folder.

To change home-folder, use

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 kill PID-number.