I dare reopen this, since the bug actually exists. Lowering severity, because this only occurs for a special cases.
In summary, if the root filesystem was created with no resize inode, and is then resized, resize2fs adds meta_bg feature to it (the same can happen in some other cases, see ext4(5) manpage). After that, grub cannot recognize the filesystem, and thus cannot boot. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org