Add a host for testing i_only_boot_zfs.

nix/configuration/hosts/i_only_boot_zfs/default.nix

@@ -0,0 +1,63 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+{
+  imports = [
+    ./hardware-configuration.nix
+    ./wrapped-disk-config.nix
+    ./distributed_build.nix
+    ./power_management.nix
+  ];
+
+  config = {
+    # Generate with `head -c4 /dev/urandom | od -A none -t x4`
+    networking.hostId = "6a05d86e";
+
+    networking.hostName = "i_only_boot_zfs"; # Define your hostname.
+
+    time.timeZone = "America/New_York";
+    i18n.defaultLocale = "en_US.UTF-8";
+
+    me.boot.enable = true;
+    me.boot.secure = false;
+    me.mountPersistence = true;
+
+    # Toggle to start writing the extlinux config which will be used by zfsbootmenu
+    # boot.loader.generic-extlinux-compatible.enable = true;
+    # boot.loader.systemd-boot.enable = lib.mkForce false;
+
+    me.optimizations = {
+      # enable = true;
+      arch = "kabylake";
+      # build_arch = "x86-64-v3";
+      system_features = [
+        "gccarch-kabylake"
+        "gccarch-x86-64-v3"
+        "benchmark"
+        "big-parallel"
+        "kvm"
+        "nixos-test"
+      ];
+    };
+
+    # Early KMS
+    # boot.initrd.kernelModules = [ "amdgpu" ];
+
+    # Mount tmpfs at /tmp
+    boot.tmp.useTmpfs = true;
+
+    # Enable TRIM
+    # services.fstrim.enable = lib.mkDefault true;
+
+    # Even when installed, we want to dhcp because this is for a VM.
+    networking.dhcpcd.enable = true;
+    networking.useDHCP = true;
+
+    me.build_in_ram.enable = true;
+    me.dont_use_substituters.enable = true;
+    me.minimal_base.enable = true;
+  };
+}