Window 8 in efi mode and Ubuntu in legacy bios mode

[Jim Byrnes]

On 10/22/2013 09:38 AM, Colin Watson wrote:
> On Mon, Oct 21, 2013 at 08:16:32PM -0500, Jim Byrnes wrote:
>> I am again trying to dual boot Win 8 and Ubuntu 13.10 on a Toshiba
>> laptop, though a different one this time.
>>
>> The only way I can get the live DVD to boot to a usable desktop is
>> to turn off the efi boot and put nomodeset in grub.
>>
>> I've done a lot of googling on dual booting and find many references
>> that basically say that both OS's must use the same scheme, ie both
>> efi or both bios.  What I can't find is the consequences of not
>> doing that. If it means to boot Win 8 I must enable efi and to boot
>> to Ubuntu I must disable it, that would be ok, but I doubt it is
>> that simple.
>
> In principle this sort of scheme should be possible.  The main gotchas I
> can think of would be:
>
>   * Your BIOS needs to support the GPT partitioning scheme.  Contrary to
>     popular belief, GPT isn't intrinsically UEFI-specific (though I'd
>     argue it's the best thing to have come out of the UEFI committee);
>     but some of them do more parsing of the partition table than they
>     need to and claim that no operating system is installed.  I've been
>     meaning to incorporate a workaround for this into Ubuntu for a while
>     but haven't yet got round to it; in the meantime
>     http://mjg59.dreamwidth.org/8035.html suggests an fdisk-based
>     workaround which ought to help.

Thanks for the link.

>   * In theory the BIOS calls that read data from disk ought to be able to
>     cope with offsets above the 2 terabyte limit (2^32 512-byte sectors).
>     In practice they often appear not to, so it's best not to install
>     Ubuntu above 2TiB if you plan to boot it in BIOS mode.  This probably
>     isn't a problem on a laptop.

Correct it is only 500 GB.

>   * If you install this way then you won't get a Windows entry in the
>     Ubuntu boot loader, or if you do then it won't work.  They should
>     still both be bootable, in that Windows' initial boot code will
>     reside in the EFI System Partition while Ubuntu's will reside in the
>     MBR and the sectors immediately after it, but you might need to keep
>     a fairly clear head during partitioning and similar operations to
>     make sure you don't break this.
>

Right now gpartd from the live dvd says the HD looks like this:

sda1 - ntfs - system - hidden,diag
sda2 - fat32 -       - boot
sda3 - ntfs -        - nsftres
sda4 - ntfs - Tl10664800H - msftdata
unallocated - (created using Win 8 to shrink sda4)
sda5 - ntfs - recovery - hidden,diag

What would you suggest for partitioning is this case?

Thanks,  Jim