dnl	$OpenBSD: prep,v 1.2 2013/10/15 13:28:07 miod Exp $
Data General AViiON systems do not require any specific preparation
steps to be able to run OpenBSD, unless you intend to share a disk between
DG/UX and OpenBSD.

    Sharing a disk between DG/UX and OpenBSD:

	Depending upon your DG/UX version, your disks will use either
	the older LDM partitioning, or the less old VDM partitioning.

	If you don't know what partitioning scheme is in use, check whether
	/usr/bin/admldisk or /usr/bin/admvdisk exist on your system. Only
	one of them will be found; if admldisk is found, your system is
	using LDM partitioning, while if admvdisk is found, your system
	is using VDM partitioning.

	OpenBSD currently doesn't recognize LDM partitioning at all,
	and will not be able to share an LDM-partitioned disk with DG/UX.

	VDM-partitioned disks are recognized to some extent: while the
	DG/UX partition themselves are not visible from OpenBSD, the
	kernel will recognize the partitioning information. If a VDM
	partition of `vdmpart' type (contiguous are), named `OpenBSD',
	is found on a VDM-partitioned disk, OpenBSD will limit itself
	to this area, leaving the remainder of the DG/UX data untouched.

	To create an `OpenBSD' vdmpart:
	- use `admpdisk -o list -p' to get a list of your current VDM
	  partitions are the areas they span on disk.
	- if there is not enough free space, consider shrinking some
	  DG/UX filesystems with
		admfilesystem -o shrink -b block_count /mount_point
	  until you have a large enough free area.
	- create a `vdmpart' named `OpenBSD' within the free space:
		admvdisk -o create -P disk_path:*:size OpenBSD
	  (the disk path, such as "sd(ncsc(0,7),0,0)" is the same as
	  reported by admpdisk).

    Booting a disk shared between DG/UX and OpenBSD:

	There can only be one set of boot blocks on a bootable disk.
	When the installer detects that the root disk is shared between
	DG/UX and OpenBSD, it will ask whether you want to install the
	OpenBSD boot blocks. If you accept, you will no longer be able to
	boot DG/UX from that disk.

	The reverse is also true: if you keep DG/UX boot blocks on the
	disk, you will not be able to boot OpenBSD automatically.

	However, the OpenBSD boot blocks can themselves be put in a
	DG/UX partition, and manually booted from there by the DG/UX
	bootblocks:
	- copy the OpenBSD boot blocks (`boot') to one of your DG/UX
	  partitions.
	- when you want to boot OpenBSD, halt your DG/UX system and,
	  at the SCM prompt, boot the OpenBSD boot blocks with the `-a'
	  option:
		SCM> b sd()boot -a
	- the bootblocks will load and prompt you for the device and
	  kernel to boot. Reply with the disk you want to load your
	  kernel from at the `boot:' prompt:
		boot: sd()bsd