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Booting 2 Windows partitions on Single HDD; One via UEFI vs One via CSM BIOS - Possible?


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#1 crashnburn

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Posted 2 weeks ago

**Booting 2 Windows partitions on Single HDD; One via UEFI vs One via CSM BIOS - Possible?**

I'd like to be able to copy/ clone a Win 8.1 BIOS-MBR booting partition from a Hard drive 1 to the HDD 2 of a GPT formatted Win 8.1 UEFI booting drive.  

The target machine is a Dell with UEFI as well as CSM BIOS so it's easy to switch the boot mode via F2 (Setup) or quickly switch via Boot Menu (F12) - Allows both UEFI / Legacy BIOS booting.   

I have just used the above switching between HDD 1 and HDD 2. But, I am wondering how it would be possible to boot OS 1 from HDD2.  

Would I have to change something in the final BCD Boot Menu of HDD 2 and/ or OS 1 partition once / after it has been cloned from HDD 1 on to HDD 2?

PS:

- I can use Paragon HDM / Acronis or Macrium to clone the partition, but I am wondering if it's possible to boot

- I have used BCDBoot, BCDEdit, EasyBCD and Visual BCD etc tools before, so specifics would be great.



#2 Wonko the Sane

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Posted 2 weeks ago

What do you mean "switching HDD 1 and HDD 2"?

Changing disk order in BIOS?

Or physically swapping disk/ports?

 

The general idea of a "plain" multiboot system (BIOS only) is that there is one "boot hard disk" or "first hard disk", the firmware (BIOS) loads at boot time (through the MBR and PBR, etc.) a bootmanager/OS loader (still residing on the "first hard disk" ) which in turn loads the operating system (that can reside on another hard disk alright).

 

With UEFI the MBR code is ignored and the firmware passes control to either a loader registered in the NVRam of the firmware or to a loader within a partition (needs normally to be FAT formatted, need a particular type if on GPT) with a "default" position/name.

 

I don't understand the "boot OS1 from HDD2".

 

If "HDD2" is GPT it won't ever boot from BIOS (unless you use a BIOS on GPT method, hybrid MBR, etc.) but even then it needs to be first disk in BIOS boot order (or however you need an intermediate step, like grub4dos to remap the disks in BIOS).

 

Can you explain what is the actual reason why you want to boot a "same" (or clone) Windows 8.1 install in BIOS and UEFI?

 

I mean, as soon as the system is actually booted, the OS will behave the same, so what is the need for this?

 

:duff:

Wonko



#3 crashnburn

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Posted 2 weeks ago

I should attach the visual so its easier to understand.

 

- Let's break it into 2 parts..

 

- GPT and MBR partitioning are different, but within the partitions, the File Systems/ Partition do remain as they are right?

i.e. Inter Partition v/s Intra Partition

e.g. An NTFS partition under an MBR scheme when > converted or copied into an existing GPT - There would/ should not be much "internal changes" i.e. Intra remains, but Inter may change?

 

- Is there an easy way to quickly change/ switch a Windows OS back & forth from a BIOS < to > UEFI booting?



#4 Wonko the Sane

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Posted A week ago

Yes, a volume is always a volume, and it corresponds  to what on MBR is usually a primary partition but that can also be a logical volume inside extended and to what on GPT is always a primary partition.

 

Technically there is a small difference between volume and partition on NTFS volumes (on both MBR and GPT style disks), because the partition is actually one single sector larger than the volume to allow a copy of the first sector of the VBR (while on all other filesystems the partition and the volume are exactly the same size).

 

The boot sequence is very different between MBR and GPT (actually between BIOS and UEFI)

 

The BIOS one (normally):

BIOS->MBR (code and data, i.e.partition table)->VBR of active partition (code and data)-> boot manager (for recent Windows BOOTMGR in root of active partition)->choice in \boot\BCD on active partition->\windows\system32\Winload.exe on *any* volume->Windows install on that volume

 

The UEFI one (also normally):

UEFI->protective MBR (data only, i.e. first entry in partition table spanning the WHOLE disk)->GPT table->a loader BOOTMGR.EFI or bootmgfw.efi  or bootx64.efi either in \boot\efi\ or \EFI\Microsoft\boot\ (or in both places) of the ESP partition (that is normally FAT formatted and NOT mounted to a drive letter)->choice in \efi\microsoft\boot\BCD on the ESP partition ->\windows\system32\Winload.efi on *any* volume BUT the ESP one->Windows install on that volume

 

There already solutions (with a few limitations) to have a GPT style disk boot from BIOS (besides from UEFI), aka "BIOS on GPT" , but until I don't understand what you are after (final goal) cannot say if it suitable to your question.

 

Also this:

 

 

- Is there an easy way to quickly change/ switch a Windows OS back & forth from a BIOS < to > UEFI booting?

is not a clear question, sure there are ways, whether they are easy is to be seen.

There is BIOS on GPT, there are Hybrid MBR's (with the usual 2.2 Tb limit), there is the possibility of re-writing the MBR (also with the usual 2.2 Tb limit), it depends on what you are after which solution may be suitable (or more suitable)

 

:duff:

Wonko


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#5 crashnburn

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Posted A week ago

I can easily press F12 at boot and choose between
- Legacy BIOS Options and
- UEFI Options - namely Windows Boot Manager - Probably points to the ESP FAT partition on HDD2 - GPT

HDD & Partition layout as shown in Paragon HDM


https://goo.gl/photo...K4CBWgv6rR9RfK8

Now, I am cloning

- W81_SP_CP2 (BIOS booting) - From HDD 1 - MBR

- To - Unallocated Space - on HDD 2 - GPT

HDD 2 already has OS_W81 (UEFI Booting) - Preinstalled

Now, given "boot mechanisms" of Legacy CSM BIOS as well as UEFI,
I believe there may be no way to boot the copy of W81 (.. Let me call it W81_BIOS) from HDD 2 until it becomes W81_EFI.

https://goo.gl/photo...MCGfPkG2ZX5CpZ6
PS - Paragon HDM does give me an option (Wizard UI link) to do/ convert/ add an EFI booting post cloning, but given its wording I am concerned/ wondering if it will "replace" / damange the existing entry for Preloaded OS_W81

I'd rather add a boot entry for W81_BIOS > EFI myself, using BCD/ EasyBCD or Easy UEFI etc type of stuff in a known controlled manner rather than Paragon HDM doing something.

Now, if I have to convert the clone W81_BIOS booting into EFI booting,
what can I do easily, so that if I ever wish to clone it back elsewhere
I can Switch back to BIOS booting?

In general:

Is there an easy way to Switch a Windows OS between EFI <> Legacy booting modes on a HDD without having to go through an extensive HDD type conversion?



#6 Wonko the Sane

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Posted A week ago

In general: 
 
Is there an easy way to Switch a Windows OS between EFI <> Legacy booting modes on a HDD without having to go through an extensive HDD type conversion?

In general, yes (or maybe no):
 
 

Also this:
 

- Is there an easy way to quickly change/ switch a Windows OS back & forth from a BIOS < to > UEFI booting?

 
is not a clear question, sure there are ways, whether they are easy is to be seen.
There is BIOS on GPT, there are Hybrid MBR's (with the usual 2.2 Tb limit), there is the possibility of re-writing the MBR (also with the usual 2.2 Tb limit), it depends on what you are after which solution may be suitable (or more suitable)

 


JFYI, in your topic title you talk of a single HDD (HDD is a common acronym for Hard Disk Drive), then you talk of two HDD's, and you ignored the questions I asked to try and understand what you are after, nor you manage to provide a clearer description of what you have, what you want to do, etc.

 

I have to conclude that - for *whatever* reasons - there is not communication between us, and as such I will declare the matter a SEP:
https://en.wikipedia..._else's_problem

 

:duff:
Wonko



#7 crashnburn

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Posted A week ago

In general, yes (or maybe no):
 
 


JFYI, in your topic title you talk of a single HDD (HDD is a common acronym for Hard Disk Drive), then you talk of two HDD's, and you ignored the questions I asked to try and understand what you are after, nor you manage to provide a clearer description of what you have, what you want to do, etc.

 

I have to conclude that - for *whatever* reasons - there is not communication between us, and as such I will declare the matter a SEP:
https://en.wikipedia..._else's_problem

 

:duff:
Wonko

C'mon Wonko dont be upset, you know we love you :) .

 

I would've rather have posted the Screenshot first (easier for me to describe and you to understand), but those drives were disconnected and I was on another machine when posting the thread. :) 

 

It is a problem of single HDD having:

- one Preloaded UEFI Win 8.1 and 

- newly cloned BIOS Win 8.1

 

It's just that the source of the clone is a BIOS Win 8.1 from another HDD. 

 

I posted the images of the pre Clone step - It's currently cloning so may take a few hours and I can upload a post-cloning scenario. 

 

Essentially I have to find some way to boot the Cloned W81_BIOS - Wondering what's the best way to do so. 



#8 Wonko the Sane

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Posted A week ago

Essentially I have to find some way to boot the Cloned W81_BIOS - Wondering what's the best way to do so. 

But the machine is UEFI and the disk is GPT, is it not? :unsure:

 

Then simply add the Cloned Windows 8.1 install to the \efi\microsoft\boot\BCD on the ESP partition.

 

How exactly you "cloned" (the double quotes are intentional) may make a difference, though, it is well possible that some adjustments are needed anyway.

 

:duff:

Wonko



#9 crashnburn

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Posted A week ago

But the machine is UEFI and the disk is GPT, is it not? :unsure:

 

Then simply add the Cloned Windows 8.1 install to the \efi\microsoft\boot\BCD on the ESP partition.

 

How exactly you "cloned" (the double quotes are intentional) may make a difference, though, it is well possible that some adjustments are needed anyway.

 

:duff:

Wonko

 

Yes. M/c has EFI and Legacy. HDD 2 is GPT. 

 

EFI Boot Entry: How do I do that? Using bcdboot? or EasyUEFI/ BCD type of tool? Recommendation? 

 

How I cloned it? (Using Paragon HDM > Copy Partition Wizard).

Do I have to make any changes/ adjustments to the "cloned" Windows ?



#10 Wonko the Sane

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Posted A week ago

Yes. M/c has EFI and Legacy. HDD 2 is GPT. 

 

EFI Boot Entry: How do I do that? Using bcdboot? or EasyUEFI/ BCD type of tool? Recommendation? 

 

How I cloned it? (Using Paragon HDM > Copy Partition Wizard).

Do I have to make any changes/ adjustments to the "cloned" Windows ?

Yes, if you didn't use a "specific cloning tool", surely you need to change the \Dosdevices drive letter assignments in the Registry, so that the partition where the "cloned" Windows has been put takes the same drive letter (I have to presume the "C:") it had originally.

 

And yes again, BCDboot might do - though I cannot say if using it might affect the "current" Windows install - I would rather use BCDedit.

Misty has written a very good guide about the BCD and how to modify its settings:

http://www.mistyrebo...Edit/index.html

but if I recall correctly has not expanded it to examples in UEFI setups.

 

I would try using either Visual BCD editor:
https://www.boyans.net/

that includes a "dual boot fix" feature (that may just work in your case) or BootIce:

http://www.ipauly.co.../11/15/bootice/

 

Making a backup of the BCD AND having a working PE to boot alternatively in case of issues is mandatory, of course.

 

:duff:

Wonko


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