Replace User's GID

• Check for Use of the new GID
  If used then replace this one first with its target.
• Update /etc/group and /etc/passwd
  • groupmod -g {newgid} {groupname}
  • usermod -g {groupname} {user}
• Check for Use of the old GID and fix
  • find / -gid {oldgid} -exec chgrp -h groupname {} \;