> I intended to net-boot a DECstation 5000/20, in order to install NetBSD,
> but I will only get this message:
> 
> KN02-CA V2.0m    (PC: 0xbfc00c78, SP: 0x801fffe8)
> Boot: 3/rz0/vmunix
> open(3/rz0/vmunix) failed: 19
> Can't boot '3/rz0/vmunix'
>
> This will be repeated continuously, without any boot-prompt visible...
> What could be wrong? 

Nothing seems wrong other than the PROM monitor variables are set for
"automatic boot after power-on" mode, and the SCSI ID #0 disk is not
available, or ULTRIX vmunix image is missing on the disk.

Try Ctrl-C several times after 'Boot: 3/rz0/vmunix' is displayed. You
should get PROM monitor prompt '>> '

Then check the PROM variable;

	>> printenv

You will see the variable 'haltaction' has value 'b'.  Then change the value

	>> setenv haltaction h

Make double checks the value of haltaction variable, do power-off-on cycle.

PROM variable 'boot' holds boot parameters.  After you complete
NetBSD/pmax installation, you should set a new value like;

	>> setenv boot "3/rz2/netbsd -a"   (double quotes are required)

This allows you to type just 'boot' command to bring the system up for
multiuser mode.   If you really want automatic boot after power-on, then
set the haltaction variable with 'b' again.

Tohru Nishimura
Nara Institute of Science and Technology