NixOS/nixpkgs — pull request #2456 by shlevy (2014-04-30 19:59:06+00:00)
Title: grub: Allow setting the boot root explicitly

If /boot is a btrfs subvolume, it will be on a different device than / but not be
at the root from grub's perspective. This should be fixed in a nicer way by #2449,
but that won't make it into 14.04