On Fri, Jun 09, 2017 at 11:36:04PM -0400, fsmithred wrote:
> On 06/08/2017 09:07 AM, Hendrik Boom wrote:
> >
> > I have a machine with both old-style MBR (fdisk) partitioned and
> > gpt-style (needs gdisk) partitioned disks. It boots using grub or
> > lilo.
> >
>
> >
> > How would booting from the GPT drives work? It's an old machine whose
> > BIOS looks for an MBR. I may well be forced to do this is my legacy
> > disk drives fail.
> >
> > If I were to transplant my GPT-formatted drives into a modern machine
> > that expects an EFI boot, would it just work? Or would I have to do
> > something major -- like repartition -- that puts my data at risk?
> >
> > -- hendrik
> > _______________________________________________
>
>
> Your old machine may or may not boot from a gpt drive. It is possible to
> put an mbr bootloader on a gpt drive. I've done that a couple of times,
> and one of the times it (or I) messed things up and had to repartition the
> drive.

There is the so-called protective MBR.. I suppose that could be the
start of a boot procedure.

>
> To boot your gpt drives on uefi hardware, you would need an efi partition
> with a bootloader. The efi partition is usually the first partition of the
> first hard drive. I haven't tried putting it in a different location. An
> easy solution would be to add a hard drive (or even a usb) and install
> enough of a system to use it to boot and add your existing system to the
> boot menu.

I have a old laptop with an EFI partition, but it has the old-style
MBR partitioning structure. The EFI partition was there when it was
new, together with a Windows XP system (which is no longer there).

As far as I've been able to tell, the contents of that partition is
garbage. It wasn't even a valid FAT-style file system, as is (or
used to be?) required by specs.

>
> Read this before you play with uefi -
> http://www.rodsbooks.com/efi-bootloaders/index.html

That looks like a very useful set of pages.

-- hendrik