Linux Change or Rename User Name and UID

Q. How do I change user name (rename user name) or UID under Linux operating system?

A. Use the usermod command to change user name under Linux. it modifies the system account files to reflect the changes that are specified on the command line.

Syntax is as follows

usermod -l login-name old-name

Where,

=> The name of the user will be changed from old-name to login_name. Nothing else is changed. In particular, the user's home directory name should probably be changed to
reflect the new login name.

usermod -u UID username

Where,

=> The numerical value of the user's ID (UID) . This value must be unique, unless the -o option is used. The value must be non-negative. Values between 0 and 99 are typically reserved for system accounts. Any files which the user owns and which are located in the directory tree rooted at the user's home directory will have the file user ID changed automatically. Files outside of the user's home directory must be altered
manually.