Unknown Filesystem - grub rescue after Windows 10 update?

Question

About a week ago Windows 10 ran its automatic updates and after that I'm unable to boot to ubuntu the way I was doing it (pressing f12 and manually selecting Ubuntu partition). Now it takes me to a black screen saying Unknown Filesystem grub rescue when I try to access it that way.

The partition isn't wiped out and Ubuntu works just fine, but I have to enter a few commands as shown in this video(Non-English) to access it. Would anyone mind helping me to "revert" whatever windows did so I can keep booting to ubuntu manually when I want to with f12 key?

Additional info - I asked this question on Reddit and I was asked

"what is the output of 'fdisk -l' in the terminal?"

This is what shows up:

Disk /dev/sda: 465,8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 7DCE2DB6-E1A6-4A44-9EC2-96460D5449EB

Device         Start       End   Sectors   Size Type
/dev/sda1       2048    923647    921600   450M Windows recovery environment
/dev/sda2     923648   1128447    204800   100M EFI System
/dev/sda3    1128448   1161215     32768    16M Microsoft reserved
/dev/sda4    1161216 244113228 242952013 115,9G Microsoft basic data
/dev/sda5  244113408 245759999   1646592   804M Windows recovery environment
/dev/sda6  245762048 830351359 584589312 278,8G Microsoft basic data
/dev/sda7  830351360 838543359   8192000   3,9G Microsoft basic data
/dev/sda8  838543360 976773119 138229760  65,9G Linux filesystem

Thank you very much in advance :)

  [1]: https://www.youtube.com/watch?v=NMMdNke-gkY

Answer 1

SOLVED for me. same exact problem here. i got a single ssd hd partitioned with a WIN10 on /dev/sda1, ubuntu server 16.04 LTS / under /dev/sda2 and swap under /dev/sda3. after updating my windows 10 got into this problem. i have just booted into ubuntu server usb stick, chose repair > repair grub, and then i chose the MBR as /dev/sda, NOT /dev/sda1!. seemed it was going to reinstall ubuntu server but nope, it just corrected fine and preserved my grub config and everything in less than 2 minutes. Just dont know why WIN10 update messed arround my MBR and cant state it wont happen again, but so far so excelent. hope it helps.

BTW i am not using EFI and my note is a Dell Vostro 3500

Answer 2

In theory, a Windows update should not have affected GRUB's ability to load its configuration file, which is what appears to have happened. I have two ideas about what has happened, and fixing one of them might correct the problem:

• Changed partition table -- If Windows modified the partition table, then that might have invalidated some partition references in GRUB. If so, you'll need to re-install GRUB, or at least adjust its configuration file, as described shortly.
• (Re-)enablement of Fast Startup and/or Hibernate -- These features can cause filesystem corruption, which might prevent GRUB from reading its first-stage grub.cfg file on the ESP. If so, disabling these features might fix the problem. I therefore recommend you start by doing precisely this. See this page for information on disabling Fast Startup and this one for information on disabling Hibernate.

I recommend you look into Fast Startup and Hibernate first. If disabling those features doesn't help, then you'll have to look into more radical solutions. These include, in order of radicalness:

• Update your GRUB configuration -- Perhaps updating your GRUB configuration will help. Since you're able to boot, you can do this by typing sudo update-grub in a Terminal window in Ubuntu.
• Re-install GRUB -- Typing sudo grub-install will re-install the main GRUB EFI binary, which might fix the problem if it's the source of the problem.
• Use Boot Repair -- The Boot Repair tool is an automated tool that helps with re-installing GRUB. It's unlikely to do any better than re-installing GRUB with grub-install, but if the problem lies in a narrow range of issues beyond what grub-install can handle, Boot Repair might do the trick.
• Switch to another boot loader -- Other boot loaders exist, and some of them are more reliable than GRUB in some cases. My own rEFInd boot manager, for instance, is less reliant on configuration files, and so is less likely to be thrown by problems related to them. You can test rEFInd on a CD-R or USB flash drive (images for both are available on its downloads page) and install the PPA or Debian package (or from the Ubuntu repository, if you're running Ubuntu 17.04) if you like it.

I recommend starting with updating your GRUB configuration file and moving to more radical solutions later, on the off chance that something drastic (Boot Repair, in particular) could cause serious problems. rEFInd run from a USB flash drive or CD-R is unlikely to create new problems because it changes nothing on your disk when run in this way; only if you install it on your hard disk will it make any permanent changes.