xauth on Mac OS X

The X11 package that comes with Mac OS X has been causing some kind of annoyances related to ssh -Y and X11 tunneling. It looks like this warning message:

[Powerbook:~] mjhsieh% ssh -Y localhost
Warning: No xauth data; using fake authentication data for X11 forwarding.

And I have been trying to tell xauth to work with me but failed all the time. Hooray! Finally this works:

[Powerbook:~] mjhsieh% xauth generate :0 .

Please be noted that this command should be used every time you gain a new IP....