Hello Colin Looks like my partition does use block lists as the --force option did restore grub MBR.
I must admit that I was sidtracked by the warning about gpt. After many experimentations with bios_grub flag (then with system-rescue-cd and fsck :-/ ), I was reluctant to try another "dangerous" option. Indeed, this whole situation begun with -20. The postinst script of -21 did not fix the problem. I'll let you decide whether that's a bug or an accidental feature. Feel free to close this bug. Thanks for the help Dominique -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org