Control: found -1 2.8.4-1 I've encountered a similar issue today:
Setting up linux-image-5.10.0-2-amd64 (5.10.9-1) ... I: /vmlinuz.old is now a symlink to boot/vmlinuz-5.10.0-1-amd64 I: /initrd.img.old is now a symlink to boot/initrd.img-5.10.0-1-amd64 I: /vmlinuz is now a symlink to boot/vmlinuz-5.10.0-2-amd64 I: /initrd.img is now a symlink to boot/initrd.img-5.10.0-2-amd64 /etc/kernel/postinst.d/dkms: dkms: WARNING: Linux headers are missing, which may explain the above failures. please install the linux-headers-5.10.0-2-amd64 package to fix this. There are no "above failures", so reading this warning message is somewhat misleading. Of course, if dkms needs some extra package, it should ideally depend on it in some way, but this seems to be nontrivial and is already covered by other bug reports, such as #762061 and #951404. But perhaps it is possible to make the above warning conditional and only print it if there actually were any errors?