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+# Provide a basic configuration for installation devices like CDs.
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+{
+  imports =
+    [ # Enable devices which are usually scanned, because we don't know the
+      # target system.
+      ../installer/scan/detected.nix
+      ../installer/scan/not-detected.nix
+
+      # Allow "nixos-rebuild" to work properly by providing
+      # /etc/nixos/configuration.nix.
+      ./clone-config.nix
+
+      # Include a copy of Nixpkgs so that nixos-install works out of
+      # the box.
+      ../installer/cd-dvd/channel.nix
+    ];
+
+  config = {
+
+    # Enable in installer, even if the minimal profile disables it.
+    documentation.enable = mkForce true;
+
+    # Show the manual.
+    documentation.nixos.enable = mkForce true;
+
+    # Use less privileged nixos user
+    users.users.nixos = {
+      isNormalUser = true;
+      extraGroups = [ "wheel" "networkmanager" "video" ];
+      # Allow the graphical user to login without password
+      initialHashedPassword = "";
+    };
+
+    # Allow the user to log in as root without a password.
+    users.users.root.initialHashedPassword = "";
+
+    # Allow passwordless sudo from nixos user
+    security.sudo = {
+      enable = mkDefault true;
+      wheelNeedsPassword = mkForce false;
+    };
+
+    # Automatically log in at the virtual consoles.
+    services.getty.autologinUser = "nixos";
+
+    # Some more help text.
+    services.getty.helpLine = ''
+      The "nixos" and "root" accounts have empty passwords.
+
+      An ssh daemon is running. You then must set a password
+      for either "root" or "nixos" with `passwd` or add an ssh key
+      to /home/nixos/.ssh/authorized_keys be able to login.
+
+      If you need a wireless connection, type
+      `sudo systemctl start wpa_supplicant` and configure a
+      network using `wpa_cli`. See the NixOS manual for details.
+    '' + optionalString config.services.xserver.enable ''
+
+      Type `sudo systemctl start display-manager' to
+      start the graphical user interface.
+    '';
+
+    # We run sshd by default. Login via root is only possible after adding a
+    # password via "passwd" or by adding a ssh key to /home/nixos/.ssh/authorized_keys.
+    # The latter one is particular useful if keys are manually added to
+    # installation device for head-less systems i.e. arm boards by manually
+    # mounting the storage in a different system.
+    services.openssh = {
+      enable = true;
+      permitRootLogin = "yes";
+    };
+
+    # Enable wpa_supplicant, but don't start it by default.
+    networking.wireless.enable = mkDefault true;
+    networking.wireless.userControlled.enable = true;
+    systemd.services.wpa_supplicant.wantedBy = mkOverride 50 [];
+
+    # Tell the Nix evaluator to garbage collect more aggressively.
+    # This is desirable in memory-constrained environments that don't
+    # (yet) have swap set up.
+    environment.variables.GC_INITIAL_HEAP_SIZE = "1M";
+
+    # Make the installer more likely to succeed in low memory
+    # environments.  The kernel's overcommit heustistics bite us
+    # fairly often, preventing processes such as nix-worker or
+    # download-using-manifests.pl from forking even if there is
+    # plenty of free memory.
+    boot.kernel.sysctl."vm.overcommit_memory" = "1";
+
+    # To speed up installation a little bit, include the complete
+    # stdenv in the Nix store on the CD.
+    system.extraDependencies = with pkgs;
+      [
+        stdenv
+        stdenvNoCC # for runCommand
+        busybox
+        jq # for closureInfo
+      ];
+
+    # Show all debug messages from the kernel but don't log refused packets
+    # because we have the firewall enabled. This makes installs from the
+    # console less cumbersome if the machine has a public IP.
+    networking.firewall.logRefusedConnections = mkDefault false;
+
+    # Prevent installation media from evacuating persistent storage, as their
+    # var directory is not persistent and it would thus result in deletion of
+    # those entries.
+    environment.etc."systemd/pstore.conf".text = ''
+      [PStore]
+      Unlink=no
+    '';
+  };
+}