Re: Chainloading isolinux.bin

[Jordan Uggla]

On Wed, Feb 3, 2016 at 11:20 PM, Andrei Borzenkov <address@hidden> wrote:
> On Wed, Feb 3, 2016 at 10:26 PM, 4javier <address@hidden> wrote:
>> Ok. Forget my last message. 2 KB was the actual dimension of the file, ls
>> shows that on my filesystem the file correctly takes 4 KB.
>>
>> Back to topic, as far as I understand, there's no way to chainload isolinux
>> bootloader from grub. Some days ago I tried the procedure through loopback
>> device, with the same result. I think the created loop device is not exactly
>> an iso filesystem, right?
>>
>
> Created loop device is exactly what is in file it is created from. The
> main problem is, once you leave GRUB this "device" is no more present.
> You would need to implement something like syslinux memdisk to hook
> into INT13 and emulate BIOS device. This is not impossible (GRUB
> already has INT13 handler to implement partition remapping).
>
> Secondary consideration remains - chanloader is not really suitable
> for it. CD-ROM boot protocol is sufficiently different from standard
> HDD handover. This again is not impossible, but someone will need to
> implement it.

And on top of that, there is the tertiary consideration that almost
any operating system that you boot this way will fail to find its root
filesystem once the bootloader hands over control to the kernel and
its native hardware access.

http://www.supergrubdisk.org/wiki/Loopback.cfg is a standard that
tries to solve this type of problem in a different way, and even
worked with older versions of System Rescue CD. (They removed the
loopback.cfg from their images for reasons that no longer apply, so I
should ask them to add it back again).

-- 
Jordan Uggla (Jordan_U on irc.freenode.net)