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Windows 7: Windows 7 & Centos 7 Dual Boot Issues - Grub2 BOOTMGR missing message

04 Feb 2017   #11
Megahertz07

Windows 7 HP 64
 
 

The default partitions on Windows depends if you have a Legacy - MBR or a UEFI-GPT system.

On a Legacy - MBR you will have a MSR -120M - RAW partition and a big NTFS where OS is installed + Linux partitions.
On a Legacy - MBR, on boot, BIOS takes to the MBR on the disk that will point to a master boot loader. This boot loader can have an option to take to another boot loader.
In your case, the boot sequence can be:
- BIOS - MBR - Linux boot loader (Grub) - options = Centos or Win boot loader- Windows
- BIOS - MBR - Win boot loader - Options = Windows or Linux boot loader (Grub) - Centos

On a UEFI - GPT you will have a UEFI 100M Fat32, MSR -120M - RAW partition and a big NTFS where OS is installed + Linux partitions.
On a UEFI - GPT, BIOS takes to the UEFI partition where can be many boot loaders. You don't have a master boot loader (Grub or win), you have both. Once you choose with one you want to boot from, it takes to the partition where the OS is.

As Grub (the master boot loader) isn't loading an option to take the sequence to windows boot loader, I suggest you to boot from a Win installation disk and do a boot repair. It will change the MBR to point to windows OS. Then, under Windows, with Easy BCD you can add an option to boot Centos.


My System SpecsSystem Spec
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05 Feb 2017   #12
os7tensed

Windows 32 bit / Centos 7 64 Bit
 
 

Thanks Mega,

Your valuable inputs kept me going and i was able to solve it eventually.

Background:
- Had 2 NTFS partition (1 System and 1 Data)
- 1 linux boot partition
- and 1 LVM

Now Path i took was
1. Decided to create Win 7 boot partition but i already had 4 partition.
2. I deleted Data NTFS partition.
3. Created 100MB Win7 Boot Partition.
4. Used bcdboot C:\Windows /s D: where D was newly created WIN7 boot partition. which became /dev/hda1 in my disk.
5. Added /dev/hda1 as menuentry in grub.d/40_custom file
6. re-run grub2-mkconfig again.
7. This time grub identified Windows boot loader, and there i was back again.
8. Left over space due to deletion of NTFS partition was added to LVM via linux. That space was then used to extend Unix partitions in LVM.

(Off course i did all this using Win 7 Recovery Disk. You will need to browse through different drives i.e. X: to find what is loaded where. Diskpart and its commands will help you in identifying drive letters)

Thanks to all of you, I was able to learn and decide just by reading so many suggestions in the forum. It was very difficult for me to take decisions, as i had lost my centos couple of times while trying out.

Cheers!
My System SpecsSystem Spec
15 Feb 2017   #13
Schrade

Windows XP
 
 

Papaya - why run OP off to another forum?

I'm sure there's someone I here, who sees and I can see the entire problem in the thread title, and fixed it many times.

Solution posted in the am here OP (did you mean MBR ??? )


edit: In fact, I don't need to get to the other pc for this one.
Insert your W7 CD / DVD, 'option repair your computer' - you need to get to a CLI (command prompt), then enter the repair command for your error (google search will give you the command).

THEN, you'll have to reinstall the GRUBLoader to correct partition because W7 repair will jam Grub.

You familiar with GRUB reinstall? And do you know the GRUB version on your Linux CD?
My System SpecsSystem Spec
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 Windows 7 & Centos 7 Dual Boot Issues - Grub2 BOOTMGR missing message




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