Thanks for the http://sourceforge.net/projects/bootinfoscript/ suggestion.
Today I made quite few experiments, and the result in brief is: no reboot problem after "dpkg-reconfigure grub-pc" and neither after the other two boot-tampering, in the 3 cases below: /boot/ tree is in a separated ext4 filesystem, root is xfs /boot/ tree is in a separated xfs filesystem, root is xfs /boot/ tree is in the root filesystem, which is ext4 deterministically appearing reboot problem in the original case: /boot/ tree is in the root filesystem, which is xfs However I can not predict the prospective reboot error, today I saw additional 2 new kind of error messeges: "error: attempt to read or write outside of partition." "error: file `/boot/grub/i386-pc/normal.mod' not found." At grub rescue prompt the command "ls /boot/grub/i386-pc/normal.mod" tend to give various error messages, like "error: not a correct XFS node." sometimes even the /boot/grub appears to be empty, or one can see the entry i386-pc in it, but it can't be listed by ls /boot/grub/i386-pc, and so on. While at the earlier missing initrd.img problem I could boot by hand, this reboot error gives no opportunity to boot by hand. However if I boot by SYSRESCCD, and I do nothing else (or work for a while) and I reboot, than this second reboot is guaranted to be successful. SYSRESCCD I think does not tamper the boot system, at least the bootinfoscript has an identical output before the unsuccessful boot, and after the successful boot. Now I try to attach the 4 results.txt files, corresponding the 4 cases, according to whether the /boot/ tree is in separate partition, and whether the partition containing the /boot/ tree is xfs or ext4. Comment: for testing the case of when /boot is in the root partition of type ext4, I installed a new Ubuntu on an other drive replaced into my linux box. ** Attachment added: "tar bzip2 of the 4 RESULTS.txt" https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1103187/+attachment/3499254/+files/results.tbz -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1103187 Title: automatic updates tend to reboot and die into grub rescue To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1103187/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs