That patent was filed back on March 25, 1987 by some folks at Xerox/PARC, which means that prior art dated before that date is helpful — and art dated before March 25, 1986 is the most useful. (That means art found in a Linux distribution may not help, seeing as how Linus Torvalds first began the Linux kernel in 1991.)
Red Hat has invited the community to join in the fight against the patent trolls by identifying prior art. They are coordinating efforts through the Post Issue Peer to Patent site, which is administered by the Center for Patent Innovations at the New York Law School, in conjunction with the US Patent and Trademark Office."
Link to Original Source