You completely missed the point. The problem is not the missing DISPLAY (you can send your X packets to anywhere you like, including :0.0), the problem is the missing *AUTHORITY* to connect to the specified X server (in this case, :0.0). You can set DISPLAY until you're blue in the face if the X server tells you to get stuffed. And it will (on any decent setup).
You are absolutely correct. My response was quick and off the cuff. I wasn't thinking the problem through.
su only changes your effective user ID but doesn't deal at all with any X stuff. sux is designed to do an su *as well* as carrying over the X connection authority and setting your DISPLAY.
How handy. However RedHat doesn't come with sux. As Perry pointed out, RedHat uses pam_xauth instead to perform this function so it is transparent to the user. Regards -- Oliver Jones § Senior Software Engineer § Deeper Design Limited. oliver(a)deeper.co.nz § www.deeperdesign.com § +64 (21) 41-2238