RE: Cannot boot from dual bios/uefi boot CD

[John Frankish]

> > > > > >> >> >> > 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) :)

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

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?

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?