[ML-General] linux dual boot win 8.1?

[WebDawg]

On Fri, Oct 9, 2015 at 6:30 AM, Michael Patton <pattoma at gmail.com> wrote:

>
> Once I get to GRUB, the system boots like the good old days..  If I do
> nothing when the computer is powered on, UEFI starts and goes to the menu
> that looks for the Windoze bootloader and boots to Win 10..
>
> ^^ This is basically what's going on here. Like Hunter said too. If I
> catch it in time I can change the boot menu and essentially select UEFI or
> the alternative. I don't necessarily mind toggling that each time, but if
> there's a way to make that not be the case, I'd love to figure that out.
>
> Since this machine came pre-loaded with windows, I suppose I can make a
> recovery CD and wipe out both OS's and reinstall them both?
>
> thx
>
>
You do need to make the decision between UEFI and MBR.  MBR reads the first
few sectors on the disk via the bios, and starts the boot process the
classic way.  With UEFI firmware, it reads a file off of a disk and
executes this file.  This file can be a lot of different things, even just
a simple shell:
https://wiki.archlinux.org/index.php/Unified_Extensible_Firmware_Interface#UEFI_Shell

If I remember correctly UEFI shells can be signed and the BIOS can be
locked to only execute certain signed UEFI shells/bootloaders.  This was a
fear when UEFI came out that MS would lock BIOS's to boot only MS signed
UEFI applications and shells with the OEM computers their software was
preinstalled on.

I think in the end they made it so you could disable the secure boot
instead of locking users out of their own OS decisions.  I have only had to
boot a UEFI shell once to flash some LSI raid cards.

The reason your USB stick would not boot is because most likely it had a
MBR and legacy partition style on it.  A machine looking for a UEFI
application/etc to boot most likely would not boot a MBR based bootstick.

With UEFI and GPT their is not MBR.  At least not in the conventional sense.

To do UEFI style booting the first requirement is a GPT partition table. (
https://wiki.archlinux.org/index.php/GUID_Partition_Table#UEFI_systems)

The second requirement is to create a special bootable EFI System
Partition.  This is simple.  It is a fat32 partition with boot set to on (I
do not know what the ESP means).  (
https://wiki.archlinux.org/index.php/Beginners'_guide#UEFI.2FGPT_examples)
You can find more information about it here too:
https://wiki.archlinux.org/index.php/Unified_Extensible_Firmware_Interface#EFI_System_Partition

I think, and please someone correct me if I am wrong, that the placement
(where) of the GPT bootable partition on the GPT partitioned disk does not
matter anymore.  It used to be MBR boot loaders could only reach out so
far.  So if you were to place a bootable partition past a certain point it
would not boot.  Anyways....

I assume since your system boots via UEFI that your disk is partitioned
GPT.  GPT is pretty cool and so many times I have been told to read about
it here:  https://en.wikipedia.org/wiki/GUID_Partition_Table  I plan on
reading it fully after this.  The one thing to pay attention to is the two
GPT headers on the disk.  If you have a disk that is GPT partitioned and
you erase the first GPT header like you used to erase an mbr and partition
table, it will not work.  GPT likes to recover from these erasures and you
have to erase the beginning and the end of the disk.

You can see attempts to erase a GPT table here:
https://moodjbow.wordpress.com/2011/08/19/erasing-gpt-disk-with-dd/

You erase the beginning of the disk and then you erase the end of the disk.

GPT also creates a protective MBR. That is so tools like fdisk see the
protective MBR and report the entire drive (or first partition if you will)
is GPT. The real partition table is the gpt table. Do not use fdisk or
legacy partition tools with GPT.

They have something out there called hybrid MBR which allows a system to
boot a legacy MBR and then push into the GPT and UEFI stuff.  It is called
a hybrid partition table.  (
https://wiki.gentoo.org/wiki/Hybrid_partition_table)  Do not do this, it is
not recommended and alot of utilities will complain about how bad this is
because it can become corrupt.

If I were you, I would backup my windows data and start fresh with UEFI
boot stuff and GPT partition styles.   I think I would disable the Secure
boot stuff which will only boot signed bootloaders too.  If this is too
complicated ( I have never done it) I would then recommend you disable UEFI
like you have spoke about doing, erase your main disk or at least the
beginning and end and install the old fashioned way with a MBR bootloader,
boot partition, linux partition, and windows partition.

You have a nice new UEFI capable system, I think I would try to UEFI boot.
It it what everyone is going to use in the future anyways.

With the UEFI stuff look at this first:
https://wiki.archlinux.org/index.php/Windows_and_Arch_dual_boot#Windows_UEFI_vs_BIOS_limitations

I would read a lot of that page because it tells you a lot about the
details between the windows and Linux UEFI boot loaders and how Grub and
stuff like that would handle it.

I think the only problem with a MBR on a modern system was large disk
support and I think that it was anything over 2TB should really use UEFI.
I can't remember the exact size.

Here is a guide that had to do with Ubuntu:
http://askubuntu.com/questions/221835/installing-ubuntu-on-a-pre-installed-windows-with-uefi

I know what you should do no matter what, if you have some data on that
disk, you need to back it up before you do anything and prepare for this to
take a while.  Also, if you do not have install media for windows 8, get it
or create it.  One of the problems that I come up against working with GPT
and UEFI is that things change and no one updates old information.

I have also seen a lot of instances when setting up things like fake raid
with intel stuff where people were taking shortcuts just to make it work.
They would manually edit grub cfg files and such instead of modifying the
grub conf files that tell grub what to look for and how to generate the
correct boot configuration.

In the end, if your linux mint updates grub to version whatever, you want
grub to be able to find both OSes and reinstall the new bootloader with the
proper config automatically.
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