I am trying to ssh with X11 forwarding into a host where I don't have a home directory. Because of that, xauth fails and X11 doesn't seem to work. I tried to specify a home-directory in advance but I guess it doesn't export env-vars to the host.

zeyer@demeter:~> HOME=/tmp ssh ares -XY
Password: 
Warning: No xauth data; using fake authentication data for X11 forwarding.
Last login: Mon Mar 28 11:52:57 2011 from demeter.matha.rwth-aachen.de
Have a lot of fun...
Could not chdir to home directory /home/zeyer: No such file or directory
/usr/bin/xauth:  error in locking authority file /home/zeyer/.Xauthority
zeyer@ares:/>

Is there any trick I can make the X11 forwarding work? I still have write access to /tmp. But I am not sure how to setup the xauth fake authentication data manually.