Hey,
I just installed KDE Neon with via an USB stick on my computer. I have two disks, on my first disk is Windows 10 and on my other disk, bought a week ago, is now KDE Neon.
So I booted from my USB stick and was able to install KDE Neon without any problems. I selected my new disk for the installation, since there is nothing else on it. When the installation was done and Neon wanted to reboot the system, I opened the boot menu in UEFI to select the correct partition. I had three options: Windows disk, Linux disk and a partition called neon. I chose neon and the GRUB console would show up, so I started Neon from there. The next day, after the PC was shut down, the neon partition wasn't there anymore, so I tried to choose the Linux disk, but this won't boot up correctly without GRUB.

I already try to repair GRUB. I deactivated Windows 10 fast boot, UEFI secure boot.

Since I don't know much about the booting process, I would really appreciate some help.

Are you sure it was a Neon partition and not possibly the USB drive still in the slot?

Not too much to go on here but your BIOS should show two hard drives. If it doesn't, start from the wall, i.e. check the plugs again. If your BIOS doesn't see them, the computer won't know they are there. Once you've fixed that can you boot with the stick again and run the command

Code: Select all

fdisk -l

It will show you details on your two hard drives /dev/sda and /dev/sdb and which one has an NTFS partition and which is the Linux drive (ext4?).

Now chroot into your Neon install (excellent howto: https://wiki.archlinux.org/index.php/Change_root) and reinstall grub.

HTH

EDIT:
There is of course nspawn as well instead of chroot. For more info: https://wiki.archlinux.org/index.php/Systemd-nspawn