I had dual-booted my system with Kubuntu 18.04 and Windows 10, and had to reinstall Windows 10 because I was messing around with the system.
During the installation, I chose the manual partition selection on where to install Windows and deleted all the partitions except for the Kubuntu and swap partitions. Meaning I inadvertently deleted the EFI partition that housed GRUB2.
I booted up a Live-USB and was able to find that the EFI partition is now on sda2, and I believe it was on sda1 before, so I'm guessing I'll have to edit the fstab file on my current Kubuntu partition as well.
I'm not entirely sure what the best route would be to reinstall GRUB2 now, since I actually deleted the partition and Windows 10 created a new EFI partition. I can't access my Kubuntu install at all as grub doesn't exist on my system any longer.
Edit:
So here is my sudo fdisk -l
Disk /dev/loop0: 1.5 GiB, 1564921856 bytes, 3056488 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/sda: 978.1 GiB, 1050214588416 bytes, 2051200368 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: D62B32DE-63E8-4C2C-9BA7-6C17B7B8120B
Device Start End Sectors Size Type
/dev/sda1 2048 1023999 1021952 499M Windows recovery environment
/dev/sda2 1024000 1228799 204800 100M EFI System
/dev/sda3 1228800 1261567 32768 16M Microsoft reserved
/dev/sda4 1261568 1048578047 1047316480 499.4G Microsoft basic data
/dev/sda5 1048578048 1468006399 419428352 200G Microsoft basic data
/dev/sda6 1468008448 2011199487 543191040 259G Linux filesystem
/dev/sda7 2011199488 2051198975 39999488 19.1G Linux swap
Disk /dev/sdb: 931.5 GiB, 1000204886016 bytes, 1953525168 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: 2A813941-89E0-495E-8B3E-A99F0578EFD3
Device Start End Sectors Size Type
/dev/sdb1 2048 1953521632 1953519585 931.5G Microsoft basic data
I mounted my sda2 to /mnt and then tried to bind mount using:
for i in /sys /proc /run /dev; do sudo mount --bind "$i" "/mnt$i"; done
This is the error I get:
mount: mount point /mnt/sys does not exist
mount: mount point /mnt/proc does not exist
mount: mount point /mnt/run does not exist
mount: mount point /mnt/dev does not exist