On Wed, Jan 18, 2017 at 10:57 PM, Scott Sullivan via talk <talk@gtalug.org> wrote:

I was recently issue an new laptop from work. Of course, being in a sysadmin position, and giving the latitude to use the tools I deem necessary, I replaced the disk and installed Fedora 25.

I felt it was also time to take the plunge with UEFI booting.

The Problem ===========

After installation, the first boot was successful. After applying updates, boot failed.

This was repeatable after a second re-install, and following updates.

Symptoms ========

System boots, and goes to a blue and white UI called 'MokManager.efi'.

Research revealed this to be a UI for enrolling encryption keys for secure boot.

http://www.rodsbooks.com/efi-bootloaders/secureboot.html MOKs—A Machine Owner Key (MOK) is a type of key that a user generates and uses to sign an EFI binary. The point of a MOK is to give users the ability to run locally-compiled kernels, boot loaders not delivered by the distribution maintainer, and so on.

Trouble Shooting ================

Firstly, I confirmed that secure boot was disabled in the laptops firmware.

Next, I booted a rescue image. Mounted the EFI partition and investigated.

mkdir /mnt/boot mount /dev/sda2 /mnt/boot # grub2 boot partition mount /dev/sda1 /mnt/boot/efi # EFI partition

We then find the MokManager.efi under the following path in our rescue environment. /mnt/boot/efi/EFI/fedora/MokManager.efi

I removed this executable to see what I could discover from the boot process.

Upon reboot, I was greeted with message of grub2-x64.efi listed as being corrupt, failing through to MokManager.efi that was now missing, and another optional efi executable that was also missing.

Repair ======

fsck.vfat /dev/sda1 - preformed removal of dirtybit> - FATs didn't agreed, selected the first one at random. Going to restore firmware anyways.

mkdir /mnt/chroot mount /dev/sda3 /mnt/chroot # root filesystem mount /dev/sda2 /mnt/chroot/boot # grub2 boot partition mount /dev/sda1 /mnt/chroot/boot/efi # EFI partition

# Make devices and process table avaliable for j in /dev /dev/pts /sys /proc; do mount -B $j /mnt/chroot$j; done

# Make DNS avaliable inside the chroot cp /etc/resolve.conf /mnt/chroot/etc/resolve.conf

chroot /mnt/chroot

# re-install grub2 EFI executables yum reinstall grub2-efi shim

# leave the chroot exit

umount /mnt/chroot/boot/efi

fsck.vfat /dev/sda1 # just to sanity check that it's still clean.

reboot

Success =======

Machine booted normally with the latest kernel form updates.

Notes =====

1) I've simplified my device names for convince of conveying the process followed. Adjust appropriately for your circumstances and disk layout.

2) In Fedora 25 is a symylink, /etc/resolv.conf -> /var/run/NetworkManager/resolv.conf, I had to copy this instead, your distro may vary.

3) There was no left over EFI partition from a previous system. This was all done on a blank hard drive.

4) Frankly, I found all of this far simpler to manage then a classical MBR based boot loader. I was able to use standard tools to investigate and repair the boot chain. No special gurb-install commands or dinking with config files.

5) None of this explains why a normal update left the boot partition in a unclean state to being with. But if it happens again, it's an easy enough repair, just a little time consuming.

-- Scott Sullivan

Thank you Mr Scott for your cogent and detailed description of both the problem and the solution you found. Wished I had had such to guide me when I set up my system on uefi 4 years ago. Thanks muchly!! Dee