Recently I had same problem.Version of grub is 2.02~beta2-22+deb8u1.I'm using debian,not ubuntu,sorry.After googled about it and found this, https://serverfault.com/questions/818600/pxe-boot-with-grub-root-variable-unset Remaking core.0 solved the problem.
$grub-mkimage -O i386-pc-pxe --output core.0 --prefix='(tftp,192.168.3.101)/boot/grub' pxe tftp '192.168.3.101' is IP address of tftp server. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1604496 Title: TFTP boot: error: time out opening '/grub/i386-pc/normal.mod' To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1604496/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
