“Shortly after the release, an easily reproducible Oops was
reported from accessing a mounted NFS filesystem. Linus
acknowledged the bug, and decided to release a quick 2.6.8.1, ‘to
make it usable for people with NFS.’ When asked why it was named
this instead of 2.6.9 using the long-standing three-digit kernel
versioning, Linus explained:“‘Well, we’ve been discussing the 2.6.x.y format for a while, so
I see this as an opportunity to actually do it… Will it break
automated scripts? Maybe. But on the other hand, we’ll never even
find out unless we try it some time…'”