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cdrom boot for sgi

i played around with booting an Indy/I2 from CDRom. I created an small
debian netinst iso filesystem containing the "boot-floppies" and the
stuff needed to put on a base system. Then i create a "fake" volume
header with tool [1]. I replaced the very first 512 bytes of the iso
with the fake volume header. The fake volume header contains no
partition (Except the volume header itself) and the volume header
spans the whole disk with all the iso9660 filesystem in it. 
Decoding the volume header with [2] shows some reasonable results
very much like the IRIX cd-roms.

Setting the SystemPartition to 
scsi(0)cdrom(6)rdisk(0)partition(8) and typeing "ls" shows the
only file "linux" which is the tftpboot.img in the usual boot-floppies

Booting the file with "linux" on the prompt gives an:

>> setenv SystemPartition scsi(0)cdrom(6)rdisk(0)partition(8)
>> ls
>> linux
2027520error on vh read

Cannot load scsi(0)cdrom(6)rdisk(0)partition(8)/linux
Error reading text section: start 0x880020000, size 0x1ef000.
Unable to execute linux

Which shows that the principle of booting from an iso image should
work but something goes wrong. I expected the files on an iso9660 image
to be contigues which i have to verify. Also the 512 vs. 2048 blocking
might be an issue. I wrote the iso with 2048 byte blocking as an iso
filesystem needs to be. In the volume header i have a blocksize of
the device mentioned as 0x200 which is 512byte - I am unshure whether 
the prom is able to read 2048 byte blocked media - I'll try once i have
a CD/RW media - Burning a CDR for every try might get a bit to expensive

[1] http://www.fall-tot-um.org/homes/flo/software/genisovh.tgz 
[2] http://www.fall-tot-um.org/homes/flo/software/decodevh.tgz

Florian Lohoff                  flo@rfc822.org             +49-5201-669912
Nine nineth on september the 9th              Welcome to the new billenium

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