NOTE: If you wish to install OpenBSD on your whole disk, i.e. you do
not want DOS or any other operating system to reside on your hard
disk, you can skip this section and go on to the section that
describes installation, below.  If you're upgrading your system from a
previous release of OpenBSD, you shouldn't have proceeded directly to
the section about upgrading; you need none of the information
presented here.

First and foremost, before beginning the installation process, MAKE
SURE YOU HAVE A RELIABLE BACKUP of any data on your hard disk that you
wish to keep.  Repartitioning your hard disk is an excellent way to
destroy important data.

Second, if you are using a disk controller which supports disk
geometry translation, be sure to use the same parameters for OpenBSD as
for DOS or the other operating systems installed on your disk.  If you
do not, it will be much harder to make OpenBSD properly coexist with
them.  Utilities exist which will print out the disk geometry which DOS
sees; some versions of DOS "fdisk" also do this.  If you have an "EIDE"
hard disk, DOS and OpenBSD probably won't see the same geometry, and you
must be careful to find out the DOS geometry and tell OpenBSD about it
during the installation.

Third (but related to the second point above), if you are using a hard
disk with more sectors than DOS or your controller's BIOS supports without
some kind of software translation utility or other kludge, you MUST
BE SURE that all partitions which you want to boot from must start below
cylinder 1024 by the BIOS's idea of the disk, and that all DOS partitions
MUST EXIST ENTIRELY BELOW cylinder 1024, or you will either not be able to
boot OpenBSD, not be able to boot DOS, or you may experience data loss or
filesystem corruption.  Be sure you aren't using geometry translation that
you don't know about, but that the DOS "fdisk" program does!

Fourth, use the DOS "fdisk" program or another partition editor to
repartition your hard disk.  Create a partition of at least 40M in
size (preferably much larger), and note its starting offset and its
length (preferably in units of disk sectors or cylinders).  You will
need that information when installing OpenBSD (and if the offset and
length are not in those units, you will have to convert them).  Once
you have created the new OpenBSD partition, mark it as having a
partition type of 0xA5 (165, in decimal).  If you used "fdisk" to
partition your disk, you will probably have to use a different
partition editor to mark the partition with the correct type.


Finally, do whatever is necessary to restore order to the partition
you took space away from.  If it was a DOS partition, you probably
will need to use "format" to create a new file system on it, and then
restore your important files from your backups.  Other operating
systems will have different needs; most will need to reformat the
partition, and if it was their "main" partition, will probably need
to be reinstalled.

Your hard disk is now prepared to have OpenBSD installed on it, and
you should proceed with the installation instructions.