How to Change Username in Linux

-l, –login NEW_LOGIN
The name of the user will be changed from LOGIN to NEW_LOGIN. Nothing else is changed. In particular, the user´s home directory name
should probably be changed manually to reflect the new login name.

Example:

Change existing username account from alice to tom:

usermod -l <new_login> <old_login>

[root@linux1]$ usermod -l alice tom

[root@linux1]$