xref: /src/distrib/notes/atari/prep

	$NetBSD: prep,v 1.4 1998/01/09 18:46:10 perry Exp $	

Note you will be modifying your HD's if you mess something up here you
could lose everything on all the drives that you mess with.  It is
therefore advised that you:

	Write down your current configurations.  Do this
	by writing down all partition info (especially their sizes).

	Back up the partitions you are keeping.

If NetBSD has a disk of it's own, you can delay the partitioning until
the installer requests you to do it. This means that you can safely skip
the rest of this section.

If NetBSD has to share the disk with another operating system, you must
take care of partitioning your harddisk before installing NetBSD; creating
space for at least root, swap and /usr partitions and possibly at
least one more for /local if you have the space.

Warning: The AHDI partioning function erases all partions on your harddisk
         even if they are not changed!
         I know this is rather stupid, but don't say I didn't warn you.

If you want to use an AHDI partitioning sceme and you want to be able to boot
directly into NetBSD, there are some constraints on the partition layout.

As you might know; every hard disk has a "root sector" that contains
information about the size of the hard disk and the partitions on the hard
disk. The root sector can only contain the neccessary data for four
partitions. Nobody thought that this limitation would cause any problems.
After all, 640 KByte should be enough.  As hard disk grew, it was neccessary
to define more than four partitions. In order to be more or less compatible
with the old format, a new type of partition entry was defined: XGM partions. 

An XGM partition is a "look over there" sign: Another root sector can be
found at the start of the XGM partition. This root sector contains the
remaining real partitions.  And this is the big mystery: Partitions defined
in the root sector of the hard disk are called "primary partitions",
partitions defined in the root sector of an XGM partition are called
"extended partitions".

The bootblock will only work if the first NBD partition is a primary
partition. This is not a limitation of NetBSD but a limitation of TOS/AHDI:
You can only boot from primary partitions.

If you are creating your partitions with HDX, you'll have to be very careful
to fulfill this rule. HDX has some very strange ideas when it comes to
extended partitions. Fortunately, you can edit this stuff: The
"Edit partition scheme of the unit" dialog box has a button label "expert".
This button is inactive unless you have defined more than four partitions.
Click on it *after* you have defined the sizes of the partitions.

A new dialog box appears on the screen. The left side contains two blocks of
partitions: The upper block always contains the first four partitions, the
lower block contains the last three partitions. If you have defined less than
7 partitions, some fields of the lower block will contain the string "unused".
Some of the partitions will be displayed in reverse video: These are the
extended partitions.

The right side contains six possible ranges for the extended partitions. It
is not possible to define your own range, you will have to use one of the
schemes offered by HDX. To quote from Ghostbusters: Choose and die.
The default scheme used by HDX is the first scheme: Extended partitions start
with the second partition and end with the second to last partition. If you
have defined 7 partitions, partitions #2 to #5 will be extended partitions,
while partitions #1, #6 and #7 will be primary partitions.

You can move the extended partition range by clicking on one of the buttons
on the right side of the dalog box. Try to find one where your first NetBSD
partition is a primary partition. Golden rules:
    * If the disk contains no GEMDOS partitions, don't use AHDI. Let NetBSD
      handle it alone.
    * If the disk contains one GEMDOS partition, make it partition #1 and
      start the extended partition range at partition #3. This allows you
      to boot from both the GEMDOS and the NetBSD partitions.
    * If the disk contains two GEMDOS partitions, use partitions #1 and #2
      for GEMDOS, partition #3 for NetBSD-root. Start the extended partition
      range with partition #4.
    * If your disks contains three or more GEMDOS partitions, you are in
      trouble. Try using partitions #1 and #2 as the first two GEMDOS
      partitions. Use partition #3 as the first NetBSD partition. Start the
      extended partition range with partition #4. Put the other NetBSD
      extended partition range.

Good luck, you'll need it...