Persist nix-index cache

home/default.nix

@@ -29,8 +29,10 @@ in
       # These imports will be scoped under this key so all settings
       # in them will be added to `home-manager.users.${username}`..
       imports = [
+        ./misc
         ./packages
         ./programs
+        ./impermanence
       ];
 
       config = {

home/impermanence/default.nix

@@ -0,0 +1,29 @@
+{
+  lib,
+  osConfig,
+  inputs,
+  ...
+}: let
+  inherit (lib) mkIf;
+  cfg = osConfig.myOptions.system.impermanence.home;
+in {
+  imports = [ inputs.impermanence.nixosModules.home-manager.impermanence ];
+
+  config = mkIf cfg.enable {
+    home.persistence."${cfg.persistentMountPoint}" = {
+      directories = [
+        ".cache/nix"
+        ".cache/nix-index"
+      ] ++ cfg.extraDirectories;
+
+      files = [
+
+      ] ++ cfg.extraFiles;
+
+      # Allow other users (such as root), to access files through the bind
+      # mounted directories listed in `directories`. Useful for `sudo` operations,
+      # Docker, etc. Requires NixOS configuration programs.fuse.userAllowOther = true;
+      allowOther = true;
+    };
+  };
+}

home/misc/dconf.nix

@@ -0,0 +1,10 @@
+{
+  dconf.settings = {
+    # This is like a system-wide dark mode swithc that some apps respect
+    # Equivalent of the following dconf command:
+    # `conf write /org/gnome/desktop/interface/color-scheme "'prefer-dark'"`
+    "org/gnome/desktop/interface" = {
+      color-scheme = "prefer-dark";
+    };
+  };
+}

home/misc/default.nix

@@ -0,0 +1,5 @@
+{
+  imports = [
+    ./dconf.nix
+  ];
+}

hosts/voyager/default.nix

@@ -37,7 +37,47 @@
       sound.enable = true;
       bluetooth.enable = true;
 
-      # TODO: Impermanence
+      impermanence = {
+        root = {
+          enable = true;
+
+          # Some people use /nix/persist/system for this, leaving persistent files in /nix subvolume
+          # I much prefer using a standalone subvolume for this though.
+          persistentMountPoint = "/persist";
+
+          extraDirectories = [
+            "/var/log"
+          ];
+        };
+
+        home = {
+          enable = true;
+          persistentMountPoint = "/persist/home";
+          extraDirectories = [
+            "Downloads"
+            "Personal"
+            "Media"
+            "dots"
+
+            ".local/share/gnupg"
+            ".local/share/wakatime"
+            ".local/share/nvim"
+            ".local/state/nvim"
+            ".local/share/zsh"
+            ".local/cargo"
+            ".local/go"
+          ];
+          extraFiles = [
+            ".config/git/git-credentials"
+          ];
+        };
+
+        # Configure automatic root subvolume wiping on boot from initrd
+        autoWipeBtrfs = {
+          enable = true;
+          devices."/dev/disk/by-label/NIXOS-FS".subvolumes = [ "root" ];
+        };
+      };
     };
 
     device = {

hosts/voyager/hardware-configuration.nix

@@ -34,12 +34,6 @@
       neededForBoot = true;
     };
 
-  fileSystems."/home" =
-    { device = "/dev/disk/by-label/NIXOS-FS";
-      fsType = "btrfs";
-      options = [ "subvol=home" "noatime" "compress=zstd:3" ];
-    };
-
   fileSystems."/data" =
     { device = "/dev/disk/by-label/NIXOS-FS";
       fsType = "btrfs";

options/system/impermanence.nix

@@ -34,6 +34,47 @@ in
           Path to a persistent directory (usually a mount point to a
           standalone partition / subvolume), which will hold the persistent
           system state files.
+
+          This should point to the entire persistent partition, this setup
+          then expects this directory to contain `passwords` and `system` subdirectories.
+        '';
+      };
+    };
+
+    home = {
+      enable = mkEnableOption ''
+        the Impermanence module for persisting important state directories.
+
+        This requires home-manager.
+      '';
+
+      extraFiles = mkOption {
+        default = [];
+        type = types.listOf types.str;
+        example = literalExpression ''[".zshrc"]'';
+        description = ''
+          Additional files in home to link to persistent storage.
+        '';
+      };
+
+      extraDirectories = mkOption {
+        default = [];
+        type = types.listOf types.str;
+        example = literalExpression ''["Downloads"]'';
+        description = ''
+          Additional directories in home to link to persistent storage.
+        '';
+      };
+
+      persistentMountPoint = mkOption {
+        default = "/persist/home";
+        description = ''
+          Path to a persistent directory (usually a mount point to a
+          standalone partition / subvolume), which will hold the persistent
+          system state files.
+
+          This does not expect any subdirectories, all of the persistent home files
+          will be put directly in here. The user should be the owner of this direcotry.
         '';
       };
     };

system/roles/workstation/programs/misc.nix

@@ -16,6 +16,9 @@ in {
 
       # gnome's keyring manager
       seahorse.enable = true;
+
+      # registry for linux (thanks to Gnome)
+      dconf.enable = true;
     };
   };
 }

system/shared/impermanence/root.nix

@@ -32,6 +32,9 @@ in
         "/etc/nixos" # NixOS configuration source
         "/etc/NetworkManager/system-connections" # saved network connections
         "/var/db/sudo" # keeps track of who got the sudo lecture already
+        # "/var/log" # I sometimes use a subvolume for this, added manually if not
+        "/var/lib/nixos"
+        "/var/lib/bluetooth"
         "/var/lib/systemd/coredump" # captured coredumps 
       ] ++ cfg.extraDirectories;