It looks like your system crashed while installing a new kernel or regenerating the initramfs. Try choosing an older kernel from the grub menu and see if that works. If it does, then run sudo apt-get install -f to try and fix it.
** Changed in: grub2 (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1396583 Title: when update grub-pc using update-manager,system can not login To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1396583/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs