Source upgrade from 5.5 to 6.X not safe?

[Clint Olsen]

I just attempted a source upgrade from 5.5-STABLE to 6.3-PRERELEASE, and it
was a disaster, more than likely because I forgot to do something.
Normally I'm saved by the fact that the operations are not so scary as to
cause problems.

Well, in this case after running 'make installkernel' and rebooting, the
system did not come back up because it got kernel fatals on reboot (fatal
trap 12: page fault while in kernel mode).  It appears that my filesystems
got marked dirty in the reboot loop that ensued, and I had to manually fsck
them.  I figured after that it might boot, but alas problems remained, so
after grabbing a disc1 image of 6.2 on CDROM I moved kernel.old back and
kernel to kernel.bad.

Now, sometimes I work fast and loose with the rules of upgrading, but I was
surprised that I managed to royally screw up things.  Any pointers would be
appreciated before I shave off a few years of my life again.

Thanks,

-Clint