added more checks for username and groupname
added more checks for username and groupname

AdrianTM/mx-user,AdrianTM/mx-user,AdrianTM/mx-user,MX-Linux/mx-user,timkb4cq/mx-user,AdrianTM/mx-user,anticapitalista/mx-user,MX-Linux/mx-user,MX-Linux/mx-user,MX-Linux/mx-user