Q. How do I create username or user groups in upper case under Linux / *BSD / UNIX operating systems?
You can create username and groups in upper case but I don't recommend it for following problems:
(a) Confusion - Some user may get confused with username VIVEK and vivek.
(b) Compatibility issues - Many protocols and certain libraries may produced compatibility issues.
The use of upper case letters for usernames or group names should be avoided under Linux / UNIX like operating systems.