portable USB disk installation

[orr721 <orr721%gmail.com@localhost>]

hello,

I have a USB disk with an installed NetBSD 8.1 system. It works
perfectly on my laptop.

However I would like to use it also on my other computers, namely on
an old hp desktop. The problem is the disk is recognized as a
/dev/rsd0 on the laptop but as /dev/rsd4 on the hp.

The first part of the boot runs correctly but then the system
complains it can't find the disk (medium not present).. Please see the
screenshot:

https://i.postimg.cc/28VFHz0D/IMG-2527.jpg

Unfortunately I am not able to use sd0 on the hp. I have tried all the
usb ports on the computer, all of them report as sd4. I have tried to
search the documentation, wiki, the lists, but I have not found a
solution. Is there some way how to make the installation disk number
agnostic? Or is there some boot parameter I have to change?

I am sorry for my noob questions I am not too experienced with the
boot process. On the other hand I have been running NetBSD on old
low-power computers with great success for a while now..

Thank you very much..

orr721