Comment 18 for bug 1536810

Unpacking linux-generic (4.3.0.7.8) ...
Processing triggers for man-db (2.7.5-1) ...
Setting up linux-image-4.3.0-7-generic (4.3.0-7.18) ...
Running depmod.
update-initramfs: deferring update (hook will be called later)
/bin/cp: cannot stat '/boot/initrd.img-4.3.0-7-generic': No such file or directory
Failed to copy /boot/initrd.img-4.3.0-7-generic to /boot/initrd.img at /var/lib/dpkg/info/linux-image-4.3.0-7-generic.postinst line 745.

Implies that, update-initramfs was called, yet it decided to defer.
No initrds created.
None possible to copy.
Boom.