Comment 3 for bug 2023771

Thank you for taking the time to report this bug and helping to make Ubuntu better. The relevant dpkg terminal log says:

E: /usr/share/initramfs-tools/hooks/zz-busybox-initramfs failed with return 1.

Can you modify this file (sudo nano /usr/share/initramfs-tools/hooks/zz-busybox-initramfs) and change the line "set -e" to "set -ex"? Then run:

sudo update-initramfs -u

This should print everything that zz-busybox-initramfs executes and will help understanding which parts failed there.