And then he moved /boot to /usr ...

[Dale Carstensen]

(I think this is a better reply than the first one I sent to sun-spots.)
The question was whether the physical placement of /boot makes a
difference.  The answer, for SunOS 4.0, is yes.  You need to know this for
restoring a lost /boot, and to set up local disk drives that have boot
capability.

Read the 4.0 man page for installboot.  The boot program that is placed on
sector 1-whatever of your boot disk does have block addresses for the
/boot program.  It is patched by the installboot program, which is not a
"dd" script as the 3.5 installboot program was.  In response to your later
message, this knowledge is probably makes you think that setup (I thought
it's name is now suninstall) is smart.

You also need to know where the two boot programs are.  Bootfile is in
/usr/stand/boot.<arch>, where <arch> is the architecture (sun3, for instance),
or /export/exec/<arch>/stand/boot.<arch> for heterogeneous servers, typically.
Protobootblock is in /usr/mdec/boot<xx>, where <xx> is the disk type, or
/export/exec/<arch>/mdec/boot<xx> for heterogeneous servers, typically.

Two other directories that suninstall and setup_client use are (for
heterogeneous servers these may be /export/exec/<arch> instead of /usr):
/usr/etc/install/proto       (most of the / file-system)
/usr/boot                    (the /sbin directory and /vmunix)