I recently installed a unix system with virtualbox and after reboot it woudnt start at all – no output..
I started a live cd and reinstalled grub. worked like a charm.
link for reinstallation of grub: link
in case some crazy error pops up (
Warning:Failed to connect to lvmetad. Falling back to device scanning.), I also made some host-run directory available in the chroot. just follow this link: link