Could not delete variable: Interrupted system call (package shim-signed 1.34.9+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:

Setting up shim-signed (1.34.9+13-0ubuntu2) ...
Installing for x86_64-efi platform.
Could not delete variable: Interrupted system call
grub-install: error: efibootmgr failed to register the boot entry: Block device required.
dpkg: error processing package shim-signed (--configure):
 installed shim-signed package post-installation script subprocess returned error exit status 1

This appears to indicate there is a problem trying to update the bootloader settings in your nvram. Is it possible you were affected by https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1734147 ? Do you know of any other reason that your firmware may be read-only?

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

Go to the hyperlink which Steve has mentioned and install the kernel. Then boot choosing the newly installed kernel option and go to recovery mode and upgrade your grub. Again reboot but choose the 4.15 kernel. And update. the shim package is installed.

I dont know the technical details as to what was the problem but my 18.04 ubuntu is working fine now.

The apt-get upgrade option does not mention the error code.

I was in fact affected by this bug, which is definitely a duplicate of https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1734147 as the fix worked great for me. I installed the first kernel, booted into it, had dpkg try again and everything worked. Booting back into the regular kernel was a snap and I purged the temporary kernel and fixed up the /vmlinuz and /initrd.img symlinks and rebooted cleanly.

The bug does mention that if you have trouble there is a second kernel to try. I had no issues using the first linked kernel http://people.canonical.com/~ypwong/lp1734147/linux-image-4.15.0-041500rc6-generic_4.15.0-041500rc6.201712312330+20170103+1_amd64.deb

found a solution at https://askubuntu.com/a/1032156 and it works...

I know of no reason that moving around the Ubuntu directory on your ESP would solve an efibootmgr failure. If the cause of this wrote for you is that your firmware has been marked read-only by the previous kernel bug in Ubuntu 17.10, this will definitely not correct that problem.

I am also affected by this, and the solution posted by Venkatesh R works for me.

for me this started happening after last upgrade to 18.04

.b

I have the same issue, Venkatesh's solution works for me but every time i do an upgrade it return.

I upgraded to 18.04 from 17.10