make sure we only have fresh systems

flake.nix

@@ -21,11 +21,21 @@
       writeCommand = krops.packages.${system}.writeCommand;
     in
     {
-      # deploy like this:
+      # deployment
+      apps.${system} = {
         #  nix run ".#deploy.sterni"
-      apps.${system}.deploy = pkgs.callPackage ./nixos/krops.nix {
+        deploy = pkgs.callPackage ./nixos/krops.nix {
           inherit writeCommand secrets;
           lib = krops.lib;
         };
+
+        #  nix run ".#test.sterni"
+        test = pkgs.callPackage ./nixos/krops.nix {
+          inherit writeCommand secrets;
+          lib = krops.lib;
+          nixosRebuildCommand = "test";
+        };
+      };
+
     };
 }

nixos/krops.nix

@@ -1,10 +1,10 @@
-{ pkgs, writeCommand, lib, secrets }:
+{ pkgs, writeCommand, lib, secrets, nixosRebuildCommand ? "switch" }:
 let
 
   # command that ensures we use flake.nix during switch
   command = targetPath:
     let
-      commandLine = "TMPDIR=/tmp nixos-rebuild switch --flake ${targetPath} -L --keep-going";
+      commandLine = "TMPDIR=/tmp nixos-rebuild ${nixosRebuildCommand} --flake ${targetPath} -L --keep-going";
     in
     ''
       echo '${commandLine}'

nixos/system/all/default.nix

@@ -28,6 +28,9 @@
 
   ];
 
+  # how much configurations should be kept?
+  boot.loader.systemd-boot.configurationLimit = lib.mkDefault 5;
+
   # default backup excludes
   backup.exclude = [ ".git" ".stfolder" ".stversions" ];