Re: Cannot boot from dual bios/uefi boot CD

[Andrei Borzenkov]

В Wed, 11 Feb 2015 19:12:54 +0400
John Frankish <address@hidden> пишет:

> > > > > > >> >> >> > On Wed, Jan 28, 2015 at 10:30 AM, John Frankish 
> > > > > > >> >> >> > <address@hidden> wrote:
> > > > > >> > >> >> > Hi,
> > > > >> > > >> >> >
> > > > >> > >> > >> > I'm trying the create a dual bios/uefi boot iso to 
> > > > >> > >> > >> > burn
> > > > >> >> > > >> > to CD/DVD and boot both bios and uefi.
> > > > >> >> > >> > >
> > > > > >> >> > >> And your grub version is?
> > > > > >> >> >> >
> > > > > > >> >> > 2.00
> > > > > > >> >> >
> > > > >> > >> Current is 2.02~beta2.
> > > > > > grub-mkrescue creates ISO that is bootable by all platforms for 
> > > > > > which grub support is installed. If your system has grub for 
> > > > > > i386-pc and > x86_64-efi (and may be i386-efi) installed under 
> > > > > > standard directory, grub-mkrescue will build ISO that includes 
> > > > > > support for all three and is bootable on all three platforms. If 
> > > > > > not, this is a bug. Which is one more reason to use it :)
> > > > > >
> > > How do I compile grub for both efi and i386-pc?
> > > 
> > > It seems like I can have --platform-efi or --platform=pc (and 
> > > --target=x86_64), but not both?
> > > 
> >
> > You can't build two platforms at the same time. Build two times and install 
> > under common prefix, like
> >
> >./configure --prefix=/usr/local/grub-test --with-platform=efi make ; make 
> >install ; make distclean ./configure --prefix=/usr/local/grub-test 
> >--with-platform=pc make ; make install 
> >/usr/local/grub-test/bin/grub-mkrescue ...
> >
> > May be we should extend grub-mkrescue to take a list of directories so it 
> > could build multi-platform image directly.
> 
> Grub-mkrescue does indeed make a legacy bios/efi boot cd that works (I note 
> that it invokes grub-mkimage) :)

You can now start with this invocation and extend it; at least you have
something that is known to work.

> 
> The trouble is that it copies all of the pc and efi modules to the iso making 
> it larger than necessary.

All modules take ~2M, so for two platforms it will be ca. 4MB if you
skip all fonts, locales and themes. What are you going to do with this
image if 4MB is too much?

> 
> I presume I can use "--modules=" to embed only the modules required to boot a 
> CD. To avoid burning another 20 coasters:
> 
> 1. What are the minimum modules required to boot only from CD/DVD and load a 
> linux OS?
> 

I do not know. Seriously :)  I would tentatively presume iso9660,
biosdisk (for PC BIOS), part_msdos, part_gpt, normal, linux and whatever
dependencies it pulls in. Basically it is whatever grub-mkrescue puts
into core.img + normal + loader for your OS.

> 2. Can I then delete all the modules from the iso and rebuild it with 
> mkisofs/xorriso or is there a way to prevent grub-mkrescue copying the 
> modules?
> 

Did you try grub-mkrescue --help?

grub-mkrescue --install-modules