Re: changing from BIOS to GPT
On 06/06/15 06:23 PM, Pascal Hambourg wrote:
Gary Dale a écrit :
I have a computer that was set up with an the older style partition
table and wanted to convert it to GPT.
May I ask why ?
Yes you may. GPT is the superior partition table, especially when
dual-booting, as it allows more partitions without getting into the
extended partition kludge.
Since the first partition started
at 2048, I figured this wouldn't be a problem. Just use gdisk to write a
new partition table after stealing some space from swap for an EFI boot
partition. Then reconfigure grub...
If you changed the disk format you must reinstall GRUB's boot loader
with grub-install so that the new core image includes the GPT module,
not just reconfigure it with update-grub.
Yes. I figured that out when it didn't boot. Unfortunately reinstalling
grub, even after purging it, didn't fix the problem.
>From the subject of your post, you seem to be confusing the boot mode
and the disk format.
The boot mode is either BIOS/legacy or (U)EFI.
The disk format is either MBR/MSDOS or GPT.
Linux and GRUB accept any combination, provided the proper version of
GRUB is installed (grub-pc for BIOS/legacy, grub-efi-amd64 for UEFI).
If you want to make a big thing out of it. :)
The HD originally had all 250G dedicated to Windows 7/Pro 64 (the way I
got it - not my choice). I shrunk that down to the smallest Windows
would allow - 137G - and created new Linux and Swap partitions that I
installed Jessie to.
Note that unlike GRUB and Linux, Windows 7 can only boot from a GPT disk
in UEFI mode or from a MBR disk in BIOS mode. If you change the
partition table format, then Windows won't be able to boot any more. If
you were able to boot Windows before converting the disk to GPT, then
the boot mode was BIOS/legacy with grub-pc.
I don't actually want to boot into Windows. I want to convert the
existing Windows install to a virtual machine on a different box at some
point. For now I just want to get a bootable Linux system.
Now I don't even to get a grub rescue prompt. I've tried reinstalling
grub in a chroot after booting with system rescue cd but that didn't
work. I've reinstalled grub to /dev/sda but again without success.
Update-grub sees the partitions but doesn't give me a bootable system.
BTW: Grub is the grub-efi-amd64 package.
Was it grub-efi-amd64 already before converting the disk to GPT or did
you install it afterwards, replacing grub-pc ?
If, the system was previously booted from grub-efi-amd64 in UEFI mode,
then an EFI system partition must have been already present and mounted
on /boot/efi. This partition is mandatory for booting in UEFI mode.
Please clarify the original situation and changes done.
Arno gave you a tip about the default EFI boot loader. The Debian
installer is also bootable in EFI mode.
As I said in a different reply, I didn't explicitly install grub-efi. I
actually wasn't even aware of its existence until I ran into the boot
problem after changing to GPT. I discovered the grub-efi-amd64
bootloader was installed when I went to reinstall grub to fix the boot
problem (reinstalling or reconfiguring is usually the easiest way to get
the system to boot again).
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