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

[H. Peter Anvin]

On 06/27/2014 12:22 AM, Thomas Schmitt wrote:
> Hi,
> 
> H. Peter Anvin:
>> It means that the .iso can be booted from a partition using any of the
>> standard MBRs (not necessarily altmbr),
> 
> But the --partok MBRs (isohdpp*) stem from altmbr ?
> 

No.  They are just slightly modified versions of the isohybrid
(isohdpf*) prefix code.

> If so: don't they need the partition number patched in ?

No.

> (If not: i have to rethink the link to article "Mbr" at
>   http://www.syslinux.org/wiki/index.php/Isohybrid#MBR_selection
> )
> 
> 
>> One of the main uses is for backup partitions -- often distros want a
>> filesystem that cannot be written for that, and iso9660 fits the bill.
> 
> Are examples known ?
> 
> Up to now i have to stay quite vague in
>   http://www.syslinux.org/wiki/index.php/Isohybrid#Images_prepared_with_--partok
> 
> "==Images prepared with --partok==
>  ISO images, which were prepared by --partok resp. with
>  MBR isohdppx*.bin, have to be copied to a partition device.
>  E.g. /dev/sdb1 rather than /dev/sdb.
>  Such an ISO partition may then be booted by chainloading or
>  by a suitable MBR at the start of the base disk device.
> "
> 
> I hope this is at least not wrong.
> Whatever, it would not suffice for myself to really create such
> a disk or USB stick. (Courageous experimenters wanted.)
> 
> ---------------------------------------------------------------
> 
> Further i wonder how --partok does play with --gpt.
> Afaik, there is no equivalent to VBR in GPT.
> So can it be that GPT in the ISO image is useless if the image is
> put into a partition ?
> Does the installing user have to compute an own GPT entry from a
> listing of the GPT in the image ? (Or from the MBR patition table
> in the image.)

You can have a VBR in GPT if you are booting BIOS.

	-hpa