Comment 13 for bug 1501884

The kernel linux-image-extras-* package intentionally calls postinst scripts even when it is rmeoved. This is required because after its removal you have still have the kernel installed though in a very slimmed down form; one which is valid for booting in a VM for instance. The postrm for the linux-image-* package will call the required postrm when and if the whole kernel is removed. We have to call all of the postinst (not just update-initramfs as we cannot know what else needs to care that the initramfs has changed; typically the bootloader which is informed of the kernel change via the /etc/kernel/* hooks. Without this the initramfs can get built without the contents of the -extras package, bootloaders can consume _that_ version and you have an unbootable system even though you subsequently installed linux-image-extra-*.

All of the scripts in the /etc/kernel/* hook directories need to be careful to view the world in the context of the installed system and idempotent against rerunning as they are part of postinst/postrm which has this requirement. If they are breaking in the face of this occuring the hooks are broken and we need to fix them.

It sounds like apt-auto-remove was incorrectly calculating the list of kernels in the past, but I understand that is fixed. Is there any other hook known to cause issues.