On 01.09.2012 08:06, Brendan Trotter wrote: > Hi, > > On Fri, Aug 31, 2012 at 11:59 PM, Lennart Sorensen > <[email protected]> wrote: >> On Fri, Aug 31, 2012 at 09:19:43AM +1000, Philip Rhoades wrote: >>> Ivo, >>> >>> Interesting idea - I particularly like the idea of booting from >>> arbitrary isos. >> >> Too bad that accessing an iso on a usb key is nothing like an actual cd >> or dvd and the sytem you boot must have support for the fact you put the >> iso on the usb key rather than as a real disc. Nothing the boot loader >> can do to change that. >> >> If it was really that simple, someone would already have made such a >> boot loader for use on usb keys. The reason it doesn't exist yet is >> that it can't exist. > > For "PC BIOS", having a USB with multiple ISO images would actually be > relatively easy. > > The USB's boot code would need to hook Int 0x15 to steal some memory, > then install code that emulates a CD (and El Torito) into the stolen memory. > Obviously you'd also hook "Int 0x13" so that the BIOS disk services are > redirected to your CD emulation code. > > I'd expect that similar would be possible for UEFI (e.g. create a special > UEFI driver that emulates CD/s). > > The main problem is after the OS on the ISO tries to take control of hardware > and fails to find its (emulated) CD. For some OSs this may not be a problem - > e.g. MS-DOS and FreeDOS (which continue to use the BIOS services > and don't take control of hardware), Linux (as long as the root > partition isn't on > the emulated CD), etc. For other OS's (Windows) it can't work. > > However, someone that wants to create a USB like this might not care about > those "unsupportable" OSs anyway. > > Finally; I'm not sure how a scheme like this would involve GRUB - you'd want > relatively specialised USB boot code (not GRUB). GRUB could (potentially) > be installed inside one or more of the ISOs, but this would be a normal > "El Torito" (or UEFI) boot as far as GRUB would know. >
This is something that can be included in GRUB. Just the amount of needed work isn't comparable with the number of additional scenarios supported (namely mostly only *DOS on ISO). > > Cheers, > > Brendan > > _______________________________________________ > Grub-devel mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/grub-devel > -- Regards Vladimir 'φ-coder/phcoder' Serbinenko
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