feat: enable impermanence

hosts/common/core/default.nix

@@ -8,6 +8,7 @@
 }: {
   imports = [
     ./inputrc.nix
+    ./impermanence.nix
     ./issue.nix
     ./net.nix
     ./nix.nix

hosts/common/core/impermanence.nix

@@ -0,0 +1,28 @@
+{
+  # State that should be kept across reboots, but is otherwise
+  # NOT important information in any way that needs to be backed up.
+  #environment.persistence."/nix/state" = {
+  #  hideMounts = true;
+  #  files = [
+  #    "/etc/machine-id"
+  #    "/etc/ssh/ssh_host_ed25519_key"
+  #    "/etc/ssh/ssh_host_ed25519_key.pub"
+  #  ];
+  #  directories = [
+  #    "/var/log"
+  #  ];
+  #};
+
+  # State that should be kept forever, and backed up accordingly.
+  environment.persistence."/persist" = {
+    hideMounts = true;
+    files = [
+      "/etc/machine-id"
+      "/etc/ssh/ssh_host_ed25519_key"
+      "/etc/ssh/ssh_host_ed25519_key.pub"
+    ];
+    directories = [
+      "/var/log"
+    ];
+  };
+}

hosts/ward/fs.nix

@@ -1,4 +1,5 @@
 {
+  lib,
   extraLib,
   nodeSecrets,
   pkgs,
@@ -39,6 +40,8 @@
     };
   };
 
+  fileSystems."/persist".neededForBoot = true;
+
   #environment.persistence."/persist".directories = [
   #  { directory = "/var/lib/acme"; user = "acme"; group = "acme"; }
   #];