server10: add znapzend backups of microvms to server8

hosts/server10/default.nix

@@ -4,6 +4,7 @@
   imports = [
     ./hardware-configuration.nix
     ./microvm-staging.nix
+    ./znapzend.nix
   ];
 
   c3d2 = {

hosts/server10/znapzend.nix

@@ -0,0 +1,27 @@
+# Quick full backups of all service MicroVM datasets.
+# server10 runs services, server8+9 have the storage.
+{
+  services.znapzend = {
+    enable = true;
+    logLevel = "info";
+    autoCreation = true;
+    # override preexisting zetups
+    pure = true;
+    zetup = {
+      "server10/vm" = {
+        recursive = true;
+        # keep a day of hourly snapshots locally on server10
+        plan = "24h => 1h";
+        destinations = {
+          server8 = rec {
+            dataset = "server8_hdd/backups/server10/vm";
+            host = "server8.cluster.zentralwerk.org";
+            plan = "2h => 1h, 7d => 24h";
+            # just always work
+            presend = "ssh-keygen -F ${host} >/dev/null || ssh-keyscan ${host} >> .ssh/known_hosts";
+          };
+        };
+      };
+    };
+  };
+}