Remove unnecessary loop in stc-ng (#348668)

Author: ElvishJerricco

nixos/tests/amazon-init-shell.nix

@@ -18,16 +18,21 @@ makeTest {
   meta = with maintainers; {
     maintainers = [ urbas ];
   };
-  nodes.machine = { ... }:
+  nodes.machine = { lib, pkgs, ... }:
   {
     imports = [ ../modules/profiles/headless.nix ../modules/virtualisation/amazon-init.nix ];
     services.openssh.enable = true;
+    system.switch.enable = true;
     networking.hostName = "";
     environment.etc."ec2-metadata/user-data" = {
       text = ''
         #!/usr/bin/bash
 
         echo successful > /tmp/evidence
+
+        # Emulate running nixos-rebuild switch, just without any building.
+        # https://github.com/nixos/nixpkgs/blob/4c62505847d88f16df11eff3c81bf9a453a4979e/nixos/modules/virtualisation/amazon-init.nix#L55
+        /run/current-system/bin/switch-to-configuration test
       '';
     };
   };

pkgs/by-name/sw/switch-to-configuration-ng/src/src/main.rs

@@ -1082,22 +1082,6 @@ won't take effect until you reboot the system.
         .subscribe()
         .context("Failed to subscribe to systemd dbus messages")?;
 
-    // Wait for the system to have finished booting.
-    loop {
-        let system_state: String = systemd
-            .get("org.freedesktop.systemd1.Manager", "SystemState")
-            .context("Failed to get system state")?;
-
-        match system_state.as_str() {
-            "running" | "degraded" | "maintenance" => break,
-            _ => {
-                _ = dbus_conn
-                    .process(Duration::from_millis(500))
-                    .context("Failed to process dbus messages")?
-            }
-        }
-    }
-
     let _systemd_reload_status = systemd_reload_status.clone();
     let reloading_token = systemd
         .match_signal(