Broken GRUB bootloader from Windows 10 Update? Here's what fixed it for me

[Lister]

I just completed my Windows 10 update, only to realize that it broke my GRUB bootloader on the first restart. It would take me to a black screen, with a command prompt and a error message...

rror: unknown filesystem
Entering rescue mode...
<grub rescue> _

Yes, "error" is misspelled.

I Googled online and found out it is a very common problem for anyone using dual-booting PCs (Mac + Windows, Linux + Windows, etc.), because apparently some Windows updates rewrite the partition tables or something. I am not a experienced Linux user but I hope that at least trying this bit could save all of you the wasted time and lost files from a reformat and reinstallation of both OSes. GRUB is apparently "lost", and needs help finding your Linux and Windows installs to continue on apparently. After following these steps, my Windows update proceeded normally.

I took these instructions and adapted them to today's commands. Since it is not referred to as "grub2" anymore and I do not use Fedora. http://www.legendiary.at/2016/01/04/...d-breaks-grub/
And this other one: https://www.linux.com/learn/how-resc...g-grub-2-linux

1. Anyways, I started by typing "ls", and taking note of all of the partitions that it listed.
2. Then I followed up by typing ls (hd#,gpt#), as how it was listed on my machine. Where "#" stands for the number. The goal is to find out where your operating systems are installed. For me, I discovered that "ls (hd0,gpt8)" returns the "ext2 filesystem".
3. I typed the following commands without quotes "set prefix=(hd0,gpt8)/boot/grub" and then "set root=(hd0,gpt8)".
4. Then I followed up with "insmod normal" and "normal", which automatically brought up our familiar bootloader. However, booting back into Kali normally is only temporary until the next reboot, where you have to once again help GRUB find your OS installs.
5. In the terminal, I typed "update-grub" and then "grub-install /dev/sda", without a number pointing to any "sda". Just "sda". It completed in a few seconds, and after rebooting my GRUB is back and working again. Something about updating the GRUB configuration and then pointing it to the correct location of our operating system installs.

Anyways, I got my Kali working again. But unfortunately, some Windows updates are more extreme, and would go as far as to delete your partitions. http://www.omgubuntu.co.uk/2016/08/w...lete-partition I don't know how to deal with THAT. I am sure, that means a forced reinstall of everything.

[m4dman]

Thank you sir. I had same problem. Hoping this will fix it.

[iojymbo]

I think the only way to mitigate this, is to install Kali on an other HDD and pointing GRUB installation on it.

[m4dman]

Fails for me at the insmod normal

Say unable to locate. Think my install is tanked and I have to start over.

[Lister]

Fails for me at the insmod normal

Say unable to locate. Think my install is tanked and I have to start over.

For EVERY partition that showed when you typed "ls" at grub rescue mode?

Out of the results I had when I typed "ls", and typing "ls (hd#,gpt#)", there were TWO partitions that showed me two promising returns. I simply tried to set prefix and set root to the other one (which would return filesystem is ext2) and then tried again which worked.

When you typed "insmod normal" and "normal", and it does not find the grub bootloader, that means that the partition doesn't contain the grub configuration files. Try setting prefix and root to the next one that you think has the grub configuration files.

[m4dman]

For EVERY partition that showed when you typed "ls" at grub rescue mode?

Out of the results I had when I typed "ls", and typing "ls (hd#,gpt#)", there were TWO partitions that showed me two promising returns. I simply tried to set prefix and set root to the other one (which would return filesystem is ext2) and then tried again which worked.

When you typed "insmod normal" and "normal", and it does not find the grub bootloader, that means that the partition doesn't contain the grub configuration files. Try setting prefix and root to the next one that you think has the grub configuration files.

Yup you were correct. I must have missed running "ls" on a partition. Loaded up. Thanks a lot sir !!!

[Lister]

Yep np.

So iojymbo was saying something about just buying another HDD and putting Kali on it, and then telling GRUB that the install is there?

Unfortunately, I am currently running a laptop, however I do have a broken internal optical drive that I can swap out, and then put in a caddy + SSD in there to complement my 750GB internal hard drive.

But I was also thinking, since I have a broken Desktop ATX box that came back from the shop, that I should convert it into a Ubuntu + Kali server. Since I have a pile of outdated hard drives with miniscule space, less than 500 GB and usually only with IDE ribbon cables attached, how do I make this thing work?

I just need a new PSU for my 9 year old Desktop. I already have two hard drives in that old thing, and a pile of even more outdated HDDs that I can use.

Can I put BOTH Kali and Ubuntu server on one of the hard drives, and then put Windows 10 on the other one?

I am also planning to install OCLHashcat, so I need the real estate for a ATI Radeon R9. The crappy cheapo motherboard is fine, it still has a working PCI-e 2.0x slot, full sized, and the replacement PSU will provide all the juice it needs. Graphics performance is not a actual concern, but utilization of as many working cores out of the video card is critical.

I just saw this news article, where some guy in a research lab, put down money for 25 GPUs into a single server box, and turned it into some sort of serious password-cracking machine. And apparently he makes money back through renting the machine to third parties to audit their passwords.

[Lister]

Ok you guys, new possible issue, probably due to the recent Windows Update.

I regularly switch between the Kali installation and Windows 10 so that I can use the best applications for both. I tried to "Copy To" a few text documents from my LInux partition over to my Windows partition, only to be confronted with the "The ____ Partition is Read-Only" error. However, I tried to fix it with altering the directory permissions on my WIndows partition (from the Linux side), as well as dragging and dropping into the root directory of the Windows partition. Same issue.

I am not certain what Microsoft had done with this new update, because copying and moving files over to my Windows installation is now being blocked. Anyhow, this isn't that big of a issue, since I can just move it into a flash drive and transfer it over from there.

Update: Dear lord. MS must have made all of the updated Windows partitions read-only. All of it. I have never seen this happen before the update.

Update: That's strange. Unmounting and remounting my Windows partitions through the Linux side makes it accessible to copying files over. Before this, attempting to "cd" over to the affected partitions and then "chmod 775 partition or folder" would still return "Read Only Filesystem" errors.