From b0a8874a93d73e0719e8376bd280278cfe2757e4 Mon Sep 17 00:00:00 2001
From: Jan-Bulthuis <git@bulthuis.dev>
Date: Thu, 29 May 2025 16:34:24 +0200
Subject: [PATCH] Set up impermanence

---
 modules/home/utilities/impermanence.nix | 34 ++++++++++++++++++++
 modules/nixos/impermanence.nix          | 42 +++++++++++++++++++++++++
 profiles/nixos/vm.nix                   |  8 +++++
 3 files changed, 84 insertions(+)
 create mode 100644 modules/home/utilities/impermanence.nix
 create mode 100644 modules/nixos/impermanence.nix

diff --git a/modules/home/utilities/impermanence.nix b/modules/home/utilities/impermanence.nix
new file mode 100644
index 0000000..a7bb2a7
--- /dev/null
+++ b/modules/home/utilities/impermanence.nix
@@ -0,0 +1,34 @@
+{ lib, config, ... }:
+
+with lib;
+let
+  cfg = config.modules.impermanence;
+in
+{
+  options.modules.impermanence = {
+    enable = mkEnableOption "Impermanence";
+    directories = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      description = ''
+        Directories that should be stored in persistent storage.
+      '';
+    };
+    files = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      description = ''
+        Files that should be stored in persistent storage.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    home.persistence."/persist/home" = {
+      enable = true;
+      hideMounts = true;
+      directories = cfg.directories;
+      files = cfg.files;
+    };
+  };
+}
diff --git a/modules/nixos/impermanence.nix b/modules/nixos/impermanence.nix
new file mode 100644
index 0000000..b0ff42f
--- /dev/null
+++ b/modules/nixos/impermanence.nix
@@ -0,0 +1,42 @@
+{ lib, config, ... }:
+
+with lib;
+let
+  cfg = config.modules.impermanence;
+in
+{
+  options.modules.impermanence = {
+    enable = mkEnableOption "Impermanence";
+    directories = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      description = ''
+        Directories that should be stored in persistent storage.
+      '';
+    };
+    files = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      description = ''
+        Files that should be stored in persistent storage.
+      '';
+    };
+    resetScript = mkOption {
+      type = types.lines;
+      description = ''
+        Script to run on boot that resets the root partition.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    boot.initrd.postResumeCommands = mkAfter cfg.resetScript;
+
+    environment.persistence."/persist/system" = {
+      enable = true;
+      hideMounts = true;
+      directories = cfg.directories;
+      files = cfg.files;
+    };
+  };
+}
diff --git a/profiles/nixos/vm.nix b/profiles/nixos/vm.nix
index c07cd0c..341a139 100644
--- a/profiles/nixos/vm.nix
+++ b/profiles/nixos/vm.nix
@@ -23,6 +23,14 @@ in
         enable = true;
         profile = "vm";
       };
+      impermanence = {
+        enable = true;
+        directories = [ "/var/lib/nixos" ];
+        resetScript = ''
+          # Revert to the blank state for the root directory
+          zfs rollback -r tank/root@blank
+        '';
+      };
       ssh.enable = true;
     };