Re: Cannot boot from dual bios/uefi boot CD

[Andrei Borzenkov]

В Sun, 1 Mar 2015 15:03:20 +0400
John Frankish <address@hidden> пишет:

> > > 
> > > 2. modified grub.cfg with "set root=(cd0)" and (perhaps not required) 
> > > "set prefix=($root)/EFI/BOOT/grub"
> >
> > This may fail if there are several CD present and grub is not booted from 
> > the first one (in firmware scan order).
> > On EFI you can set prefix to ()/path (grub-mkimage ... -p "()/boot/grub"); 
> > "()" as disk designation means "set root to
> > whatever device I was booted from" and path is taken from prefix then.
> 
> Sorry, but I'm not sure I figured that out correctly. Taking my example 
> above, should I use:
> 
> set root=()
> set prefix=($root)/EFI/BOOT/grub
> 

No. '()' is magical only when used as initial prefix (grub-image
--prefix). Once grub is past initialization those commands are taken
verbatim and the first one likely results in error.

If you use grub-mkimage --prefix='()/EFI/BOOT/grub' you do not need
to set it later in grub.cfg - grub should automatically set $root to
the device (e.g. cd0) it was booted from and prefix will be changed
accordingly (e.g. to (cd0)/EFI/BOOT/grub).