I could have guessed I'd find the answer just after posting, but perhaps this will make it easier for the next googler. I had written:
Summary: After upgrade from Lenny to Squeeze, I can no longer execute X apps using sudo in an ssh session. Why not, and how can I restore this ability?
A careful reading of the manpage for the /etc/sudoers file (man 5 sudoers) yields this insight, under EXAMPLES: # Run X applications through sudo; HOME is used to find the # .Xauthority file. Note that other programs use HOME to find # configuration files and this may lead to privilege escalation! Defaults env_keep += "DISPLAY HOME" It looks like the newer version of sudo no longer preserves $HOME by default (although, the above notwithstanding, it does keep $DISPLAY). Adding the following line to my /etc/sudoers restored my ability to run X apps via sudo: Defaults env_keep += "HOME" Hope someone else finds this helpful. Ted Ruegsegger