Hmm this seems related to GRUB trying to find something on a NFS (or other network mounted) disk.
However Ubuntu 16.04 is in ESM support only, please report a new bug if you are still experiencing similar issues on modern Ubuntu ** Changed in: grub2 (Ubuntu) Status: New => Won't Fix -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1575588 Title: package memtest86+ 5.01-3ubuntu2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1. Installation was made in process update of diskless station from 15.10 to 16.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1575588/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs