{{tag>[linux fedora grub2 efi]}}

=====Fedora - reinstall / fix grub2 UEFI====
~~NOTOC~~

Some hints to fix booting your favourite OS. Tested with Fedora 25 and Windows 10.
====Fedora====
  * Boot from live USB
  * Switch to root and mount the needed filesystems:<code>
sudo -i

mkdir -p /mnt/sysimage
mount /dev/fedora/root /mnt/sysimage

mount --bind /dev /mnt/sysimage/dev
mount --bind /run /mnt/sysimage/run
mount -t devpts pts /mnt/sysimage/dev/pts
mount -t proc proc /mnt/sysimage/proc
mount -t sysfs sys /mnt/sysimage/sys 

modprobe efivarfs
mount -t efivarfs efivarfs /mnt/sysimage/sys/firmware/efi/efivars
</code>
  * Copy the resolv.conf to have some networking in the chroot:<code>
mkdir -p /mnt/sysimage/var/run/NetworkManager
cp /var/run/NetworkManager/resolv.conf /mnt/sysimage/var/run/NetworkManager
</code>

  * Enter the chroot and mount /boot and /boot/efi filesystems:<code>
chroot /mnt/sysimage

mount /boot
mount /boot/efi</code>

  * Reinstall grub2:<code>
dnf -y reinstall grub2 grub2-efi grub2-efi-modules shim
grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
</code>
  * Check if entry exists in EFI menu:<code>efibootmgr</code>
  * Add entry if it is missing:<code>
grep efibootmgr /var/log/anaconda/program.log 
22:47:35,458 INFO program: Running... efibootmgr
22:47:35,477 INFO program: Running... efibootmgr -c -w -L Fedora -d /dev/nvme0n1 -p 2 -l \EFI\fedora\shim.efi

#Run the command found above:
efibootmgr -c -w -L Fedora -d /dev/nvme0n1 -p 2 -l '\EFI\fedora\shim.efi'
</code>
  * (optional) Add another OS for example:<code>efibootmgr -c -w -L Windows -d /dev/nvme0n1 -p 2 -l '\EFI\Microsoft\Boot\bootmgfw.efi'</code>
  * (optional) Change the boot order:<code>efibootmgr -o 1,0</code>
  * (optional) Delete entry:<code>efibootmgr -b 0 -B</code>
  * (optional) Change timeout:<code>efibootmgr -t 2</code>
  * Unmount filesystems and reboot:<code>
umount /boot/efi
umount /boot
exit
umount /mnt/sysimage/sys/firmware/efi/efivars
umount /mnt/sysimage/sys
umount /mnt/sysimage/run
umount /mnt/sysimage/proc
umount /mnt/sysimage/dev/pts
umount /mnt/sysimage/dev
umount /mnt/sysimage

reboot
</code>

====Windows 10====
  * Modify the path for the Windows boot manager to Fedora:<code>bcdedit /set {bootmgr} path \EFI\fedora\shim.efi</code>
  * Alternatively you can use EasyUEFI to edit the entries.