GRUB No longer shows up

edit

Sounds to me like the the boot-order in NVRAM has reverted to Windows by default. This happens sometimes on my HP laptop as well. The simplest solution is to boot Fedora and run efibootmgr which looks like this:

$ efibootmgr
BootCurrent: 0001
BootOrder: 0002,0001,2001,2002,2004
Boot0000* USB Hard Drive (UEFI) - Samsung Flash Drive
Boot0001* Fedora
Boot0002* Windows Boot Manager

You might see some extra items. On my computer, BootCurrent is 0001, which is a reference to Boot0001, which is the Fedora entry. The Boot0002 entry is for Windows. Note though that the BootOrder says Windows first, Fedora second. You probably see that too but maybe with different number assignments. To change the order, using my numbers as an example:

$ sudo efibootmgr --bootorder 1,2

And confirm it.

$ efibootmgr
BootCurrent: 0001
BootOrder: 0001,0002
Boot0000* USB Hard Drive (UEFI) - Samsung Flash Drive
Boot0001* Fedora
Boot0002* Windows Boot Manager

Now the order is 0001 (Fedora) first, and 0002 (Windows) second. Note, you can either include or exclude the prefix zeros. And you don't even have to include each boot entry.

All that normally matters is what's first in the bootorder because as long as that is a working entry, that's what boots. So what's the point of having something listed second and third? It's just a fallback. Now if in your case the BootOrder is already correct but it still boots Windows first, that means something else is wrong. The first step to figure that out is for you to post what you get for efibootmgr -v but for now I'm just going to assume BootOrder switched back to Windows being first.

The first time you boot up, grub2 will appear on your first hard disk, so you should check the disk for confirmation and status. If the grub values are modified and set incorrectly, serious problems may occur.

Changing from BIOS Legacy Mode to UEFI will cause boot problems, and will force booting of GRUB2 on a system running in UEFI mode.

Perhaps if you have two disks and you use a different operating system, use grub2 on Linux to update the boot state as follows:

First, grub2 will work on the first hard disk without changing the state set in the BIOS.

[Case1. 1Disk - 2 OS or 2Disk 2 OS]

 Check the disk status. [fdisk /dev/sdX] p Enter  q Enter
 # fdisk /dev/sda             [MS-Windows System]
 # fdisk /dev/sdb             [Linux- Fedora System]
or
 # fdisk /dev/sda1            [MS-Windows System]
 # fdisk /dev/sda2            [Linux- Fedora System]

[Case 2. grub2 update and re-install for MBR(Master Boot Record) System]

 # grub2-mkconfig -o /boot/grub2/grub.cfg 
 or
 # grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg

Sometimes the location of grub.cfg may be different. [/boot/efi/EFI/fedora/grub.cfg ]

 # grub2-install /dev/sda

Do NOT run grub2-install if you intend to boot in UEFI mode. [ @villykruse ]. Use disk to distinguish between mbr and gpt. If UEFI is supported, check gpt when checking the fdisk status.

if the boot settings are correct, you can get new the boot status and will be update for grub2 in boot process

After boot linux, logging in to linux, update grub2 with the command, and let me know the progress so that you can better troubleshoot the problem. Please let me know your results and i will be update further.

It sounds like your BIOS is set up to boot the wrong disk. Check your BIOS settings to see if you can change the boot order to be the Fedora drive first. I have had the same problem and this fixed my issue. Your Fedora grub should include an entry for the Windows install also.