Subject: Re: Why did it hang? (How to boot on second device?)
To: None <jfw@jfwhome.funhouse.com>
From: Charles M. Hannum <mycroft@ai.mit.edu>
List: current-users
Date: 07/02/1995 09:50:54 
   After putting a fresh set of binaries on the "a" partition of my
   second SCSI drive (sd1), I attempted to boot with that as the root.
   (i386; told the boot prompt "sd(1,a)/netbsd -s".  It gets through the
   autoconfiguration, says "changing root device to sd1", then "WARNING:
   no swap space found" (which is correct, there is no "b" partition on
   that drive), then it just sits there.

Sounds like you didn't populate /dev.