How do I boot off of a 2nd controller?

[Doug Alan]

I've been having some problems trying to boot a VAXstation-II from a
disk drive on a second disk controller.  I know that the kernal on the
root partition of the drive in question is good, because that is our
normal root partition.  I also know that the boot blocks are good
because they were copied (dd count=16 bs=1b) from the drive that is
currently being booted from, and both controllers are MSCP
controllers.

This is what I am doing:

	>>>b/3 dub0

The "u" meaning MSCP controller, the "b" meaing the second controller,
and the "0" meaning the first drive on that controller.  Well, all
this seems to work.  The drive whirs for a little while, and then I
get the Unix boot prompt:

	Boot
	:

To this I add the following:

	Boot
	:ra(4,0)vmunix

The "4" meaning ra4, which is what the drive I want to boot off of is
known as, and the "0" meaning the first partition on this drive.
Shortly after typing this, the machine halts, instead of booting, and
the ">>>" prompts have been output on top of any error message that
might have been there.  Anyone have any idea what I am doing wrong?
I've tried using "2" - "7" instead of "4", in case I'm just using the
wrong number, but none of them worked, either.

I'm also a little bit puzzled about how the boot program is supposed
to know what the two numbers in "ra(4,0)vmunix" mean.  According to
the man page for 'reboot(8)', the first number is the unit number and
the second number is the partition number.  I don't understand how the
boot program is supposed to know what unit number is where.  I can
configure the kernal so that any drive has any unit number I want it
to have.  Also, how does the boot program know where different
partitions begin?  I can configure the kernal so partitions begin
wherever I want them to.  How does the boot program know where I've
configured the various partitions to begin?

|>oug /\lan