What's magic about "setup"?

[geaclib!lethe!dave at uunet.uu.net]

A follow-up to my question about the problem of getting the boot into the
right place for a sun rom to find it... (remember the site that copied
/boot to /usr?)

What is magic about the construction of the sun root filesystem?  Two
different individuals here in Tranna have had the doubtful pleasure of
building root filesystem with mkfs (or newfs), populating it with restore
or tar and having the system hang somewhere in the booting sequence.  Who
can tell me what "setup" knows that I don't?

--dave (now if it was a pdp-11, I'd know what to do.
        but if it **was** an 11, it would be too small) c-b