Set convenience variables: 

export veid=777
export mountPoint=/mnt

Download NixOS minimal install archive.

Extract the archive: 

mkdir /vz/private/$veid
tar -xjf nixos-install-archive.tar.bz2 -C /vz/private/$veid

Prepare for installation: 

mount -o bind /vz/private/$veid $mountPoint
bash $mountPoint/nix/store/nixos-prepare-install checkout-sources copy-nix

Configure NixOS: 

nano $mountPoint/etc/nixos/configuration.nix

This is the minimal working nixos config(don't forget to replace $IP with the IP you're going to assign to the guest): 

{pkgs, config, ...}:
{
  boot.loader.initScript.enable = true;

# fake root since nixos requires this to be set
  fileSystems = [ {
    mountPoint = "/";
    label = "nixos";
    options ="noauto";
  } ];

  networking = {
    defaultGateway = "$IP";
    interfaces = [ {
      name = "venet0";
      ipAddress = "$IP";
    } ];
  };
}

Install: 

bash $mountPoint/nix/store/run-in-chroot "/nix/store/nixos-bootstrap --install --no-grub"

Configure OpenVZ: 

vzctl set $veid --applyconfig vps.basic --save
vzctl set $veid --ipadd $IP --save

Edit /etc/vz/conf/$veid.conf to increase ram and disk space available. NixOs occasionally needs more than 256M of RAM for nixos-rebuild.

Known issues:

  • df is broken unless you symlink /proc/mounts to /etc/mtab, it is overwritten on every reboot.
  • stopping container takes a lot of time
  • openvz can't change the IP of the container, you need to change it by hand in nixos config in addition to openvz settings.
  • Sometimes tty services keep restarting over and over. They can safely be stopped by "stop ttyX", X = 1 to 6.
Retrieved from "http://nixos.org/wiki/Install_NixOS_as_OpenVZ_guest"