configuration.nix

{ config, pkgs, ... }:

{
  imports =
    [ # Include the results of the hardware scan.
      ./hardware-configuration.nix
    ];

  # Use the GRUB 2 boot loader.
  boot.loader.grub.enable = true;
  boot.loader.grub.version = 2;
  
  boot.loader.grub.device = "/dev/sda"; # or "nodev" for efi only

  boot.kernelParams = [ "net.ifnames=0" ];  # Don't rename interfaces
      networking = {
        defaultGateway = "172.31.1.1";
        defaultGateway6 = {
          address = "fe80::1";
          interface = "eth0";
        };
        nameservers = [ "8.8.8.8" "8.8.4.4" ];
        interfaces.eth0 = {
          ipv4.addresses = [
            {
              address = "95.216.152.211";
              prefixLength = 27;
            }
          ];
          ipv6.addresses = [
            {
              address = "2a01:4f9:c010:1043::";
              prefixLength = 64;
            }
          ];
        };
  };

  system.stateVersion = "18.09"; 

}

install.log

root@kexec:/mnt/etc/nixos]# nixos-install
building the configuration in /mnt/etc/nixos/configuration.nix...
GC Warning: Bad initial heap size 100000 - ignoring it.
[167 built, 373 copied (1188.0 MiB), 75.0 MiB DL]
GC Warning: Bad initial heap size 100000 - ignoring it.
copying channel...
GC Warning: Bad initial heap size 100000 - ignoring it.
installing the boot loader...
setting up /etc...
Initializing machine ID from KVM UUID.
updating GRUB 2 menu...
installing the GRUB 2 boot loader on /dev/sda...
Installing for i386-pc platform.
/nix/store/j5h48r8biwznxwlhyq3hi5mk5cj026k8-grub-2.02/sbin/grub-install: warning: File system `ext2' doesn't support embedding.
/nix/store/j5h48r8biwznxwlhyq3hi5mk5cj026k8-grub-2.02/sbin/grub-install: warning: Embedding is not possible.  GRUB can only be installed in this setup by using blocklists.  However, blocklists are UNRELIABLE and their use is discouraged..
/nix/store/j5h48r8biwznxwlhyq3hi5mk5cj026k8-grub-2.02/sbin/grub-install: error: will not proceed with blocklists.
/nix/store/cbs8gnyjs164wwcmz1yv7mszy7p37nr1-install-grub.pl: installation of GRUB on /dev/sda failed