Re: Doubts about Debian8.1 DVD ppc64el image

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

> > debian-8.1.0-ppc64el-CD-1.iso 
> debian-7.8.0-powerpc-CD-1.iso

So your algorithm is missing the Apple Partition Map and possibly
the HFS to which it points.

The bootability of debian-8.1.0-ppc64el-CD-1.iso is indicated by
fulfilling the CHRP demands:
- value 0x96 at byte offset 450 (MBR partition type)
- values {0,0,0,0} at byte offset 454 (partition 1 start LBA)
- values {0x55, 0xaa} at byte offset 510 (MBR signature)
- the four bytes at offset 458 as little endian number should tell
  the size of the ISO image file divided by 512 (partition 1
  block count).

The "powerpc" ISOs fulfill these criteria too. Overwrite their
first two bytes by zeros and check whether they still boot. If so
then your firmware does not need HFS.

My notes about CHRP say:
"The firmware looks up a file /ppc/bootinfo.txt which in SGML-ish tag
<boot-script> contains firmware commands.
E.g. to execute the binary /boot/grub/powerpc.elf as first stage of GRUB2:
  <boot-script>boot &device;:\boot\grub\powerpc.elf</boot-script> 
"
(Learned from Vladimir Serbinenko ,
http://stuff.mit.edu/afs/sipb/contrib/doc/specs/protocol/chrp/chrp1_7a.pdf ,
https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/W51a7ffcf4dfd_4b40_9d82_446ebc23c550/page/PowerLinux%20Boot%20howto)


Have a nice day :)

Thomas