nixos/tests/systemd-initrd-networkd-ssh: Test with backdoor not LUKS

nixos/tests/systemd-initrd-networkd-ssh.nix

···
 
   nodes = {
     server = { config, pkgs, ... }: {
-      environment.systemPackages = [ pkgs.cryptsetup ];
-      boot.loader.systemd-boot.enable = true;
-      boot.loader.timeout = 0;
-      virtualisation = {
-        emptyDiskImages = [ 4096 ];
-        useBootLoader = true;
-        # Booting off the encrypted disk requires an available init script from
-        # the Nix store
-        mountHostNixStore = true;
-        useEFIBoot = true;
-      };
-
-      specialisation.encrypted-root.configuration = {
-        virtualisation.rootDevice = "/dev/mapper/root";
-        virtualisation.fileSystems."/".autoFormat = true;
-        boot.initrd.luks.devices = lib.mkVMOverride {
-          root.device = "/dev/vdb";
-        };
-        boot.initrd.systemd.enable = true;
-        boot.initrd.network = {
+      testing.initrdBackdoor = true;
+      boot.initrd.systemd.enable = true;
+      boot.initrd.systemd.contents."/etc/msg".text = "foo";
+      boot.initrd.network = {
+        enable = true;
+        ssh = {
           enable = true;
-          ssh = {
-            enable = true;
-            authorizedKeys = [ (lib.readFile ./initrd-network-ssh/id_ed25519.pub) ];
-            port = 22;
-            # Terrible hack so it works with useBootLoader
-            hostKeys = [ { outPath = "${./initrd-network-ssh/ssh_host_ed25519_key}"; } ];
-          };
+          authorizedKeys = [ (lib.readFile ./initrd-network-ssh/id_ed25519.pub) ];
+          port = 22;
+          hostKeys = [ ./initrd-network-ssh/ssh_host_ed25519_key ];
         };
       };
     };
···
         status, _ = client.execute("nc -z server 22")
         return status == 0
 
-    server.wait_for_unit("multi-user.target")
-    server.succeed(
-        "echo somepass | cryptsetup luksFormat --type=luks2 /dev/vdb",
-        "bootctl set-default nixos-generation-1-specialisation-encrypted-root.conf",
-        "sync",
-    )
-    server.shutdown()
-    server.start()
-
     client.wait_for_unit("network.target")
     with client.nested("waiting for SSH server to come up"):
         retry(ssh_is_up)
 
-    client.succeed(
-        "echo somepass | ssh -i /etc/sshKey -o UserKnownHostsFile=/etc/knownHosts server 'systemd-tty-ask-password-agent' & exit"
+    msg = client.succeed(
+        "ssh -i /etc/sshKey -o UserKnownHostsFile=/etc/knownHosts server 'cat /etc/msg'"
     )
+    assert "foo" in msg
 
+    server.switch_root()
     server.wait_for_unit("multi-user.target")
-    server.succeed("mount | grep '/dev/mapper/root on /'")
   '';
 })