hmm did both xterm +ls -e su - postgres
xterm su - postgres
in terminal. They opened a xterminal window with same bash-2.05b$ prompt
tried both in that terminal window just in case that was what you meant and got
xlib: connection ro ":0.0" refused by server
xlib:no protocol specified.
Not a big deal just wondered why the prompt was different, apart from that everything works ok