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Dual boot - LOST GRUB

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Vsat
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Dual boot - LOST GRUB

#1 Post by Vsat »

Hi, I'm running Win7 & Debian11 on a desktop PC.
It was working fine, accessing both OS via Grub.

Then I removed some older Windows installations on other drives, and this messed up Windows boot, so had to run BOOTREC from Win install media.
This fixed Win7 but no longer see the Grub menu.

I know that the EXT partition is SDC5
I cannot access Debian at all.

Repair mode from Debian install CD fails to load. (fails to copy win32loader/linux)

Thanks!
Last edited by Vsat on 2021-12-06 02:31, edited 1 time in total.

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Re: Dual boot - LOST GRUB

#2 Post by Vsat »

correction- SDC5

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quixote
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Re: Dual boot - LOST GRUB

#3 Post by quixote »

It's been a long time since I've dealt with this, so I'll have to look it up before providing any actual help. But I just wanted to say, like in the Hitchhiker's Guide to the Galaxy: Don't panic. Your Debian is still there and grub can be rebuilt.

The problem is that Windows refuses to see anything except Windows, so grub has to be rebuilt from outside it. In a situation like yours, if I remember right, that'll involve booting from a USB thumbdrive or sdcard and then doing a bunch of tedious command line stuff. But you'll get it set back up.

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Re: Dual boot - LOST GRUB

#4 Post by pcalvert »

Boot with Super GRUB2 Disk and use it to boot your Debian system. Once you are back in Debian again, reinstall GRUB. There are other ways to repair GRUB, but this way is one of the easiest.
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Re: Dual boot - LOST GRUB

#5 Post by p.H »

Vsat wrote: 2021-12-06 02:20 Repair mode from Debian install CD fails to load. (fails to copy win32loader/linux)
How are you trying to launch the Debian installer ? Not from Windows, I hope ? You must boot it from the BIOS, select advanced > rescue, follow the steps, select the root partition and select reinstall GRUB.

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Re: Dual boot - LOST GRUB

#6 Post by Vsat »

pcalvert wrote: 2021-12-06 11:38 Boot with Super GRUB2 Disk and use it to boot your Debian system. Once you are back in Debian again, reinstall GRUB. There are other ways to repair GRUB, but this way is one of the easiest.
Hi pcalvert, many thanks for the super grub suggestion, that's new to me, will give it a go.
I'm new to Linux so simple is good!
thanks!!

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Re: Dual boot - LOST GRUB

#7 Post by Vsat »

p.H wrote: 2021-12-06 12:52
Vsat wrote: 2021-12-06 02:20 Repair mode from Debian install CD fails to load. (fails to copy win32loader/linux)
How are you trying to launch the Debian installer ? Not from Windows, I hope ? You must boot it from the BIOS, select advanced > rescue, follow the steps, select the root partition and select reinstall GRUB.
Hi PH, I put the installation CD in the drive, and tried to get to command line from there, but I think its sand boxed.
I don't know how to boot it from BIOS?
I'm going to try super grub2 first, then'll post back.
thanks for your help!

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Re: Dual boot - LOST GRUB

#8 Post by p.H »

Vsat wrote: 2021-12-06 17:20 tried to get to command line
This is not what I suggested.
Vsat wrote: 2021-12-06 17:20 but I think its sand boxed.
What do you mean ? What is "it" ?
Vsat wrote: 2021-12-06 17:20 I don't know how to boot it from BIOS?
How then did you boot the installer and install Debian ?

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Re: Dual boot - LOST GRUB

#9 Post by Vsat »

pcalvert wrote: 2021-12-06 11:38 Boot with Super GRUB2 Disk and use it to boot your Debian system. Once you are back in Debian again, reinstall GRUB. There are other ways to repair GRUB, but this way is one of the easiest.
Hi Pcalvert,
I successfully created a supergrubdisk and booted to that, and could immediately access Linux Debian again.
But supergrub didnt have an option to repair the grub menu (as far as I can see).
But having accessed Debian, I was able to repair grub
sudo update-grub feedback told me the partition to use
sudo grub-install /dev/sdc then fixed it.

So thank you everyone for your suggestions, a great relief to be fixed!!

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Re: Dual boot - LOST GRUB

#10 Post by Legion99 »

I have had this problem trying to dual boot UEFI Win 10 and MINT. Can't see why the solution isn't going to work which was to abandon Grub altogether.
I think GRUB is well past it's use by date anyway.
So, boot with whatever Debian live CD you prefer. Install rEFInd bootloader -->https://www.rodsbooks.com/refind/ then reboot to rEFInd menu. It certainly worked for me.

Once boot is sorted the boot menu can be edited how you want it.

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