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From: geert@ahds.UUCP (Geert W.T. Jonkheer CCS/TS)
Newsgroups: comp.os.minix
Subject: Re: Booting minix (st) from a double sided floppy drive?
Message-ID: <1976@ahds.UUCP>
Date: 24 Apr 91 07:21:11 GMT
References: <51610@nigel.ee.udel.edu>
Organization: Ahold NV, Zaandam, Netherlands, EEC
Lines: 54

Thanks to all who respond to my message of booting minix from
a double sided disk. The solutions (summary) are given below:

 1) Type 2,8 for the current root device, when minix 
    asks for it  (Specify root dev). (Adam and many others). 

 2) Change include/minix/boot.h and compile de kernel. 

hange  DRAMIMAGEDEV in DEV_FD0 + 8 oid.
 is the minor device nummer of /dev/dd0
                            			(Frans)

 3) A solution to boot minix directly from one floppy: 
    (Direct copy from the letter I received from Adam David)
     
=================================================================
There are 2 distinct operations involved.
A) Modify the minix system to boot from rootFS on device 2,8 without asking.
   It is also necessary to modify the bootsector of the floppy to load the
   minix image from after the end of the rootFS on a DD disk.
B) Copy the new minix image to the correct place on the rootFS disk and replace
   the bootsector with the new version.

The modifications are to minix/config.h, tools/boot.s, tools/type.s (and also
tools/Makefile). Basically it's just a matter of setting
#define ASKDEV 0
#define BOOTDEV <changed>
I think there was also one more #define to change, possibly related to 
bootdrive it could have been in another header file. I'm telling you this from
memory, so I might be wrong. It's really easy, all you need is to get the 
idea of how it's done and you can figure it out for yourself (honest).
In the assembler code there is a 'clr.w d6' which needs to be changed to
'move.w #startsec,d6' where you have already equated startsec to the correct
sector offset on the disk. For instance, I have a 360k rootFS and I use 
the next available sector number 720 as the start of the minix image 
(exactly as produced starting with a boot sector).

To get the minix image onto the rootFS (again using my figures for example):
dd if=minix.imx of=/dev/dd0 seek=720
dd if=minix.imx of=/dev/dd0 count=1

If you've done it right then you can boot direct from the same floppy.

At present the minixFS makes no use of the bootblock on floppies. In case this
ever changes I defined a bootFS entry in type.s so that the actual boot code
(after the first bra.s instruction) starts at offset $80 on the disk sector.
Due to irregularities in the assembler the 'bra.s *+$80' instruction had to be
coded as '.data2 0x607E'

-Adam David-
adamd@rhi.hi.is
=================================================================

Geert.