nixpkgs/nixos/modules/virtualisation/nova-image.nix

# Usage:
# $ NIXOS_CONFIG=`pwd`/nixos/modules/virtualisation/nova-image.nix nix-build '<nixpkgs/nixos>' -A config.system.build.novaImage

{ config, lib, pkgs, ... }:

with lib;

{
  system.build.novaImage = import ../../lib/make-disk-image.nix {
    inherit pkgs lib config;
    partitioned = true;
    diskSize = 1 * 1024;
    configFile = pkgs.writeText "configuration.nix"
      ''
        {
          imports = [ <nixpkgs/nixos/modules/virtualisation/nova-image.nix> ];
        }
      '';
  };

  imports = [
    ../profiles/qemu-guest.nix
    ../profiles/headless.nix
  ];

  fileSystems."/".device = "/dev/disk/by-label/nixos";

  boot.kernelParams = [ "console=ttyS0" ];
  boot.loader.grub.device = "/dev/vda";
  boot.loader.grub.timeout = 0;

  # Allow root logins
  services.openssh.enable = true;
  services.openssh.permitRootLogin = "without-password";

  # Put /tmp and /var on /ephemeral0, which has a lot more space.
  # Unfortunately we can't do this with the `fileSystems' option
  # because it has no support for creating the source of a bind
  # mount.  Also, "move" /nix to /ephemeral0 by layering a unionfs-fuse
  # mount on top of it so we have a lot more space for Nix operations.

  /*
  boot.initrd.postMountCommands =
    ''
      mkdir -m 1777 -p $targetRoot/ephemeral0/tmp
      mkdir -m 1777 -p $targetRoot/tmp
      mount --bind $targetRoot/ephemeral0/tmp $targetRoot/tmp

      mkdir -m 755 -p $targetRoot/ephemeral0/var
      mkdir -m 755 -p $targetRoot/var
      mount --bind $targetRoot/ephemeral0/var $targetRoot/var

      mkdir -p /unionfs-chroot/ro-nix
      mount --rbind $targetRoot/nix /unionfs-chroot/ro-nix

      mkdir -p /unionfs-chroot/rw-nix
      mkdir -m 755 -p $targetRoot/ephemeral0/nix
      mount --rbind $targetRoot/ephemeral0/nix /unionfs-chroot/rw-nix
      unionfs -o allow_other,cow,nonempty,chroot=/unionfs-chroot,max_files=32768 /rw-nix=RW:/ro-nix=RO $targetRoot/nix
    '';

    boot.initrd.supportedFilesystems = [ "unionfs-fuse" ];
  */

}