[root@nixos:~]# nixos-install
building the configuration in /mnt/etc/nixos/configuration.nix...
copying channel...
installing the boot loader...
setting up /etc...
updating GRUB 2 menu...
installing the GRUB 2 boot loader on /dev/vda...
Installing for i386-pc platform.
/nix/store/r4s1icl6nsqi1ck92wclrvgnl0ld2316-grub-2.02/sbin/grub-install: error: cannot find a device for /boot/grub (is /dev mounted?).
/nix/store/vx15jkfgdsdhqjdl5cmbrm9b6v3gdd1d-install-grub.pl: installation of GRUB on /dev/vda failed