nixos/cloudstack-image: initial import

Cloudstack images are simply using cloud-init. They are not headless
as a user usually have access to a console. Otherwise, the difference
with Openstack are mostly handled by cloud-init.

This is still some minor issues. Notably, there is no non-root user.
Other cloud images usually come with a user named after the
distribution and with sudo. Would it make sense for NixOS?

Cloudstack gives the user the ability to change the password.
Cloud-init support for this is imperfect and the set-passwords module
should be declared as `- [set-passwords, always]` for this to work. I
don't know if there is an easy way to "patch" default cloud-init
configuration. However, without a non-root user, this is of no use.

Similarly, hostname is usually set through cloud-init using
`set_hostname` and `update_hostname` modules. While the patch to
declare nixos to cloud-init contains some code to set hostname, the
previously mentioned modules are not enabled.

nixos/maintainers/scripts/cloudstack/cloudstack-image.nix

@@ -0,0 +1,23 @@
+# nix-build '<nixpkgs/nixos>' -A config.system.build.cloudstackImage --arg configuration "{ imports = [ ./nixos/maintainers/scripts/cloudstack/cloudstack-image.nix ]; }"
+
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  imports =
+    [ ../../../modules/virtualisation/cloudstack-config.nix ];
+
+  system.build.cloudstackImage = import ../../../lib/make-disk-image.nix {
+    inherit lib config pkgs;
+    diskSize = 8192;
+    format = "qcow2";
+    configFile = pkgs.writeText "configuration.nix"
+      ''
+        {
+          imports = [ <nixpkgs/nixos/modules/virtualisation/cloudstack-config.nix> ];
+        }
+      '';
+  };
+
+}

nixos/modules/virtualisation/cloudstack-config.nix

@@ -0,0 +1,40 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  imports = [
+    ../profiles/qemu-guest.nix
+  ];
+
+  config = {
+    fileSystems."/" = {
+      device = "/dev/disk/by-label/nixos";
+      autoResize = true;
+    };
+
+    boot.growPartition = true;
+    boot.kernelParams = [ "console=tty0" ];
+    boot.loader.grub.device = "/dev/vda";
+    boot.loader.timeout = 0;
+
+    # Allow root logins
+    services.openssh = {
+      enable = true;
+      permitRootLogin = "prohibit-password";
+    };
+
+    # Cloud-init configuration.
+    services.cloud-init.enable = true;
+    # Wget is needed for setting password. This is of little use as
+    # root password login is disabled above.
+    environment.systemPackages = [ pkgs.wget ];
+    # Only enable CloudStack datasource for faster boot speed.
+    environment.etc."cloud/cloud.cfg.d/99_cloudstack.cfg".text = ''
+      datasource:
+        CloudStack: {}
+        None: {}
+      datasource_list: ["CloudStack"]
+    '';
+  };
+}