[syslinux] How is a isohybrid --partok image to be used ?

[Thomas Schmitt]

Hi,

i am trying to document the MBR selection by isohybrid option --partok.

I assume it is related to "altmbr.bin" as described in
http://www.syslinux.org/wiki/index.php/Mbr
But there i read
"altmbr.bin [...] boots from a partition with fixed number, see below."

The "see below" probably refers to
"The altmbr.bin (all 3 variants) is only 439 bytes long, -- one extra
 byte should be set to the number of partition to boot from."

I do not see in isohybrid.c any provisions to write that number.
There is option -e to choose a partition entry, but this only
causes a particular partition table entry to mark the overall
ISO filesystem. It does not cause special manipulation of the MBR.

Do i get it right that the MBR of a --partok isohybridized image
shall become the VBR of a partition, which the user has to create
by other means before copying the ISO image into it ?

If yes, how should the MBR of the overall disk be created resp.
manipulated to boot the ISO ?

Are there examples known of bootable ISOs which where treated
with isohybrid --partok ?


Have a nice day :)

Thomas