I've upgraded an old system by installing over it and it looks like 1.6.2
has a new installboot.  Of course old manpages are in the way, so I removed
them.  Based on the new manpage I tried:
/usr/sbin/installboot /altroot/boot /usr/mdec/biosboot.sym
But that complains and doesn't work.  How am I supposed to make /altroot
a bootable file system?