Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cwjcc!tut.cis.ohio-state.edu!rutgers!att!lzaz!hcj
From: hcj@lzaz.ATT.COM (HC Johnson)
Newsgroups: comp.sys.atari.st
Subject: Re: Hard Disk Partitioning Tutorial
Summary: Yes, you can partition after the fact
	 IF you can read sector 0
Keywords: TOS SUPRA BMS Hard disk Partitioning
Message-ID: <474@lzaz.ATT.COM>
Date: 17 Mar 89 14:00:08 GMT
References: <457@lzaz.ATT.COM> <308@laas.laas.fr>
Organization: AT&T ISL Lincroft NJ USA
Lines: 36

In article <308@laas.laas.fr>, ralph@laas.laas.fr (Ralph P. Sobek) writes:
> 
> Howard C. Johnson's article ( <457@lzaz.ATT.COM> ) on partitioning was
> very interesting.  I have an SH204 with partitions C, D, and E.  I
> would very much like to split my 10 meg E partition into 2 smaller
> partitions, GEM and Mac.  Can it be done without destroying partitions
> C and D?  If so, how?
> 
The whole point of my article was that a partition is just numbers.
They are easily changed.

You will need a means to read, modify, and rewrite sector 0 of the hard disk.
This is easiest if you are using MINIX.  Otherwise look into the Abacus
books #13, ST Disk Drives, Inside and Out.  They have sample code to
read/write sector 0.

Then I would suggest you copy the 12 bytes for partition 2 (0,1,2) into 
the slot for partition 3.  Then change the size of partition 2 to N, a 
smaller than it was.  Then change the start of partition 3 to 
(start of partition 2 + size of partition 2).   Then change the size of 
partition 3 to (whats there - size of partition 2.

part 2: GEM 1 ORIG_START_2 ORIG_SIZE_2
copy to part 3
part 3: GEM 1 ORIG_START_2 ORIG_SIZE_2
let N be new size for part 2:
part 2: GEM 1 ORIG_START_2 ORIG_SIZE_2 - N  /* manually subtract */
part 3: GEM 1 ORIG_START_2 + N  ORIG_SIZE_2 - N /* manually add/subtract */

The Supra disk software includes a sector editor, also.


Howard C. Johnson
ATT Bell Labs
att!lzaz!hcj
hcj@lzaz.att.com