The following is for Linux. It may or may not work for Unix. Try it and see.
Method #1: if user already created
syntax:
Step 1. Type vi /etc/passwd
Step 2. Scroll down to username and change the following to a 0 (zero):
username:x:uid:gid::/etc/home:/bin/bash
Step 3. Hit the ESC button, then hit the key combination Shift:, then type wq!, then hit the enter button.
[size=18]"Note"[/size]
Be careful. If you make a mistake, just hit the ESC button, then hit the key combination Shift:, then type q!, then hit the enter button. Then begin at step 1 again.
Method #2: if user not yet created
syntax:
adduser -o -u 0 username
the letter o is for override and the number 0 is to set the uid to zero like the root's uid(user id).