migrate to impermanence?

machines/109-199-104-83/configuration.nix

@@ -4,6 +4,10 @@
   machine,
   ...
 }: {
+  imports = [
+    ./impermanence.nix
+    (modulesPath + "/profiles/qemu-guest.nix")
+  ];
   # roundcube config
   services.roundcube = {
     enable = true;
@@ -46,8 +50,12 @@
   # system config
   system.stateVersion = "25.11";
   nix.settings.experimental-features = ["flakes" "nix-command"];
-  imports = [(modulesPath + "/profiles/qemu-guest.nix")];
   fileSystems."/" = {
+    device = "none";
+    fsType = "tmpfs";
+    options = ["defaults" "size=60%" "mode=755"];
+  };
+  fileSystems."/nix" = {
     device = "/dev/sda1";
     fsType = "ext4";
   };

machines/109-199-104-83/impermanence.nix

@@ -0,0 +1,30 @@
+{
+  environment.persistence."/nix/persist" = {
+    enable = true;
+    hideMounts = true;
+    directories = [
+      # logs
+      "/var/log"
+      "/var/lib/systemd/coredump"
+
+      # users
+      "/var/lib/nixos"
+
+      # private ssh keys
+      "/etc/ssh"
+
+      # mailserver
+      "/var/vmail"
+      "/var/dkim"
+      "/var/lib/dovecot"
+      "/var/lib/postfix"
+      "/var/lib/postgresql"
+      "/var/lib/redis-rspamd"
+      "/var/lib/roundcube"
+      "/var/lib/secrets"
+    ];
+    files = [
+      "/etc/machine-id"
+    ];
+  };
+}