Problem with GRUB and possibly Ubuntu

Question

I used to have just Windows 10 installed, but quite recently I decided to dual boot it with Ubuntu. This worked just fine. Yesterday I had an annoying issue where GRUB wouldn't show me the usual OS selection screen, only a GRUB terminal. I've had this once before and I believe it went away after a restart that time, however this time it didn't go away. So I tried to boot into one of the operating systems manually by spamming F8 during startup. I managed to get into Windows, but with Ubuntu I was out of luck. It gave me an error when trying to boot saying there was a security issue and that this could be resolved by disabling Secure Boot. Later I found out this didn't work either; it would just send me to the same GRUB terminal.

I tried using an Ubuntu live USB stick to run Boot-Repair. When I did, it said that the boot repair was successful, but there was still no GRUB boot menu. I checked under Advanced options and all the tabs that mentioned GRUB were gray.

I then checked the disks in the live Ubuntu environment using sudo fdisk -l and sudo blkid. When I did this I saw that none of the partitions matched the properties of Ubuntu that are mentioned in this article under the terminal section.

I will include some information about versions, etc. at the end.

In conclusion I can use the F8 key to get into Windows 10 with no problem, but when I don't press F8 I see a GRUB terminal. Using F8 to get to Ubuntu doesn't work. Boot-Repair doesn't work, and I don't see the partition Ubuntu was on. How do I get Ubuntu back, and if it's gone, how do I make sure that everything works like it used to (the dual boot setup) with or without a fresh Ubuntu install? I don't mind losing the files on the Ubuntu part, but the files on Windows 10 are quite important.

• GRUB version (shown in GRUB terminal): 2.02
• Windows version: Windows 10 Home version 1803 build 17134.765
• Ubuntu version: I don't know the exact version but I've updated Ubuntu last week (writing on 5-6-2019) but there was a new Ubuntu update that I didn't install before this issue.
• Live Ubuntu version: Ubuntu 18.04

Spamming F8 let's me choose between:

• Windows Boot Manager (P0: WDC ...)
• UEFI OS (P0: WDC ...)
• ubuntu
• ubuntu (P0: WDC ...)

One ubuntu option doesn't have the (P0: WDC ...) bit and the part in dots matches between the different options. Either ubuntu option brings me the GRUB terminal, and so does not pressing the F8 key.

fdisk and blkid results:

Note: the sdb1 drive that says Ubuntu is just the Ubuntu live USB.

sudo parted -l result:

Windows Disk Management:

^{(Click image to enlarge)}

Answer 1

The minimum disk space required to install Ubuntu is 10GB, and the recommended disk space is at least 25GB. If the information in the screenshots is correct, you do not have much of an alternative except to do a fresh installation of Ubuntu. Furthermore all the information in the 4 screenshots can't be correct, because the results of Windows Disk Management and Ubuntu terminal programs are contradictory.

The unallocated disk space in Windows Disk Management is split into two 9.77GB partitions which is not the ideal way of allocating space on the disk from the standpoint of recycling the unallocated disk space to install Ubuntu. Furthermore Windows Disk Management recognizes a different partition layout than sudo fdisk -l and sudo parted -l. This raises the question of whether anything that you do in Windows Disk Management to further change the partition layout of disk /dev/sda will be recognized by the Ubuntu installer or whether it will just add new problems to the problems that you already have. Your C: partition has 859.60GB, 41% of which is free. 60GB (or more depending on how much disk space you need to store files in your home directory) from this partition could be used to install Ubuntu on. sudo parted -l identifies this partition as partition 5 of size 923GB.

Before you make any changes to the partitioning, it would be wise to consider that your first priority should be to ensure the integrity of your files on the Windows partitions. This would be a good time to back up these files, if you have not already done so. You have a 1TB external hard drive that can be used to save backups.