Setting up X on a headless server

This was hard to figure out. I've had a little Debian fileserver for about a year, and after discovering Cygwin X, wanted to be able to use X applications on that machine, rather than boring old PuTTY sessions.

I configured an awful lot of X stuff on the machine, but nothing worked. Every time I tried to start xclock, there was no server running, the connection was refused, or various other problems ended up getting in the way. I finally figured out the problem had nothing to do with X. It was ssh: the X11Forwarding option in /etc/ssh/sshd_config was turned off. I turned that on, tried again, and it worked.

Keywords for others having the same problem: audit client rejected connection refused xlib display xauth localhost