Package: grub-pc Version: 2.02+dfsg1-11 Severity: normal >From logs, the following events seem to have happened:
grub-pc was upgraded under unattended-upgrades. This was when the udev bug changed disk path. Grub-pc appears to have tried installing in the old nonexistent path; I assume this part depended on unattended- upgrades not allowing it to use debconf to ask for a new path. Apt logs only show "grub-install: error: cannot find a GRUB drive for ...". After this, no core.img file existed on the machine. grub-pc.postinst uses the existence of a core.img file to determine the kind of installation the machine has; with it absent, the package entered a permanently broken state where further upgrades or dpkg-reconfigure did nothing. There are at least two things here which can be considered bugs: 1. If there is no interactive debconf frontend available, the package goes ahead and calls grub-install with known incorrect arguments. 2. Using the existence of core.img to determine the type of install is too fragile when this file can be erased by a failed grub-install call, and after this happens the package state can not be recovered by normal means (I used a manual grub-install call to restore the file). I haven't tried reproducing problem 1. Bug 2 can be mostly reproduced by manually running "grub-install /dev/wtf"; after running that, you can see that "dpkg-reconfigure grub-pc" no longer works. BTW the grub-install manual page lists most options, then repeats the "Install GRUB on your drive." description, and lists the same options again.