> So the idea would be to splat the ISO image onto FBA disk and then
> define a minidisk to cover just the extents used by the image, and
> then treat the image from Linux as a raw FBA device with an iso9660
> filesystem on it.
I've done this. Works.
Been thinking about it for YEARS, and finally got it done.
The way it turned out was easier than I originally imagined.
The result is an ISO formatted CD which can be eyeballed on a
Windows PC (or any Linux machine) and can also be byte-for-byte
copied to FBA media and IPLed. If Hercules would map a CD-ROM
to a 9336 or 3370, Herc could boot directly from the CD.
(But at this time, Herc requires a byte-for-byte copy of
the CD into an ordinary disk file, then boot.) [sigh]
It uses FBA IPL, rather than SCSI/SAN IPL. (I do not know
if SCSI/SAN IPL would render FBA IPL unusable, but hope to see.)
I found that the ISO filesystem reserves some 32K at the start.
(maybe 64K; ran empirical checks twice with different results;
then too, I may have messed up my octal kon-ver-zhuns)
I sized an FBA disk to look like a CD (about 600M) and defined
a partition starting after 64K and running up to the 512M line.
(Wrestling with 'fdisk', the nearest start boundary was 1M.)
Then defined the boot partition there (starting at 512M).
I put an EXT2 FS into that main partition just for work space.
THIS is where things got easier than I originally imagined.
With EXT2 "root" in the big partition and EXT2 "boot" in the
after 512 partition, you get a bootable FBA disk. Duh!
So I now have two of these, and copy parts of the bootable
EXT2-on-FBA over to the ISO-on-FBA, along with the .iso file
created by 'mkisofs'. It looks like this:
0CD1 600M ..................... 0CD2 600M
IPL text at 0 ................. IPL text at 0
part 2 at 1M .................. part 2 at 1M
part 1 at 512M ................ part 1 at 512M
In this case, the partition numbers are out of order.
Ignore 'fdisk' if it complains about that.
CD1 gets two EXT2 FS, "root" in part 2 and /boot in part 1.
Run 'zipl' and the IPL text gets laid down at offset zero
rendering the disk perfectly bootable. Next, make an ISO FS
of that root filesystem (I kept boot mounted under it,
but you don't strictly have to), then copy
first 64K of CD1 to same range on CD2
resulting .iso file, SKIPPING 64K!, to offset 64K of CD2
part 1 of CD1 to part 1 of CD2
To summarize: take the working IPL text from CD1
and the physical content of its "partition 1",
then combine with the .iso file. Voi-la! Bootable CD.
-- R;
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