[syslinux] isohybrid boot from logical partition

Thomas Schmitt
Thu, 29 Dec 2016 08:35:07 -0000

Hi,

Duncan Elliot wrote:
> As far as I can see, this essentially trims off the first 3 bytes of the
> custom isohybrid MBR image before applying it to the ISO.

You probably mean this line:

        memcpy(mbr, &isohdpfx[hd0 + 3 * partok], MBRSIZE);

The indize do not apply to bytes but to byte arrays of size MBRSIZE.

    extern unsigned char isohdpfx[][MBRSIZE];

(hd0 + 3 * partok) selects a particular MBR template from an array of
six MBRs. See also
  http://www.syslinux.org/wiki/index.php?title=Isohybrid#MBR_selection

It tells which isohd*.bin file is selected by which combination of options.


> does anyone have suggestions for what modification I'd need to look at
> to support this on a logical parttion?

Sorry, not me. One will probably have to analyze the code of MBR and/or
isolinux.bin to find out why it is not working with your situation.

(Did you already tell which partitions exist and in which one do you want
 to put your ISO ?)


Have a nice day :)

Thomas