package shim-signed 1.34.4+13-0ubuntu2 failed to install/upgrade: installed shim-signed package post-installation script subprocess returned error exit status 1

The error in your log is:

Processing triggers for shim-signed (1.34.4+13-0ubuntu2) ...
No MOK found.
dpkg: error processing package shim-signed (--configure):
 installed shim-signed package post-installation script subprocess returned error exit status 1

I cannot see anything in your log which explains why shim-signed is being triggered. What are the contents of /var/lib/dkms on your system?

This may be fixed by dkms 2.3-3ubuntu9 which has just been accepted into bionic-proposed. It may or may not be the cause of your failure. Having once been triggered, however, the fixed dkms package will not automatically fix your upgrade problem.

Please do paste the contents of /var/lib/dkms on your system.

My bug #1766637, regarding recent MAAS deployments of Bionic, has been marked a duplicate of this one. The MAAS logs in that bug seem to indicate that there's a problem accessing /sys/firmware/efi:

Setting up shim (13-0ubuntu2) ...
Setting up libefivar1:amd64 (34-1) ...
Processing triggers for libc-bin (2.27-3ubuntu1) ...
Setting up sbsigntool (0.6-3.2ubuntu2) ...
Setting up libefiboot1:amd64 (34-1) ...
Processing triggers for man-db (2.8.3-2) ...
Setting up mokutil (0.3.0-0ubuntu5) ...
Setting up secureboot-db (1.1) ...
Can't access efivars filesystem at /sys/firmware/efi/efivars, aborting

For me, the problem is recent -- deployments done a week ago succeeded fine, but today they're failing. (I've done no deployments in the past few days, so I'm not sure exactly when the problem began.)

This last passed our vmtest on April 19th, using shim-signed 1.33.13-0ubuntu2

[ 247.040363] cloud-init[993]: ['install-grub', '--uefi', '--update-nvram', '/tmp/tmpfx83n0fv/target']
[ 247.044415] cloud-init[993]: moved etc/default/grub.d/50-cloudimg-settings.cfg out of the way
[ 247.047645] cloud-init[993]: carryover command line params: console=ttyS0
[ 247.051047] cloud-init[993]: curtin uefi: installing grub-efi-amd64 to: /boot/efi
[ 247.054015] cloud-init[993]: + echo before grub-install efiboot settings
[ 247.057152] cloud-init[993]: before grub-install efiboot settings
[ 247.058732] cloud-init[993]: + efibootmgr
[ 247.061410] cloud-init[993]: Timeout: 0 seconds
[ 247.064404] cloud-init[993]: No BootOrder is set; firmware will attempt recovery
[ 247.068672] cloud-init[993]: + dpkg-reconfigure grub-efi-amd64
[ 247.072156] cloud-init[993]: Replacing config file /etc/default/grub with new version
[ 247.079448] cloud-init[993]: Processing triggers for shim-signed (1.33.1+13-0ubuntu2) ...
[ 247.085449] cloud-init[993]: No DKMS packages installed: not changing Secure Boot validation state.
[ 247.087634] cloud-init[993]: + update-grub
[ 247.090150] cloud-init[993]: Generating grub configuration file ...
[ 247.098979] cloud-init[993]: Warning: Setting GRUB_TIMEOUT to a non-zero value when GRUB_HIDDEN_TIMEOUT is set is no longer supported.
[ 247.104824] cloud-init[993]: Found linux image: /boot/vmlinuz-4.15.0-15-generic
[ 247.108435] cloud-init[993]: Found initrd image: /boot/initrd.img-4.15.0-15-generic
[ 247.112684] cloud-init[993]: Adding boot menu entry for EFI firmware configuration
[ 247.114281] cloud-init[993]: done

<snip>

[ 248.537884] cloud-init[993]: + grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu --recheck
[ 248.541008] cloud-init[993]: Installing for x86_64-efi platform.
[ 248.543631] cloud-init[993]: Installation finished. No error reported.
[ 248.546292] cloud-init[993]: + echo after grub-install efiboot settings
[ 248.548636] cloud-init[993]: after grub-install efiboot settings
[ 248.551045] cloud-init[993]: + efibootmgr
[ 248.551977] cloud-init[993]: Timeout: 0 seconds
[ 248.554185] cloud-init[993]: BootOrder: 0000
[ 248.556021] cloud-init[993]: Boot0000* ubuntu

This started to affect our solutions-qa test runs yesterday/last night at some point - we can no longer deploy bionic on uefi systems:

We're not using dkms packages at all; here is the failed install log from maas:

http://paste.ubuntu.com/p/NVdV4tZvJW/

Status changed to 'Confirmed' because the bug affects multiple users.

This would be a duplicate of bug 1766627.