treewide: drop impermanence in favor of preservation

flake.lock

@@ -251,21 +251,6 @@
         "type": "github"
       }
     },
-    "impermanence": {
-      "locked": {
-        "lastModified": 1734772301,
-        "narHash": "sha256-mQEQQzCTUlDiEw/EbblB510P/GQOmIPtKoJrqDqeGVc=",
-        "owner": "nix-community",
-        "repo": "impermanence",
-        "rev": "0ab2f858dfefe73402eb53fbe6a3bad4f6702d5f",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-community",
-        "repo": "impermanence",
-        "type": "github"
-      }
-    },
     "lanzaboote": {
       "inputs": {
         "crane": "crane",
@@ -397,6 +382,21 @@
         "type": "github"
       }
     },
+    "preservation": {
+      "locked": {
+        "lastModified": 1734453061,
+        "narHash": "sha256-FfHXIRuyTmv9/U3ioOu3jnij1NPA6ywk7GdC3A+FMAA=",
+        "owner": "WilliButz",
+        "repo": "preservation",
+        "rev": "9ee89d71475c0f4a6e97ed4a9169e377222ea8d6",
+        "type": "github"
+      },
+      "original": {
+        "owner": "WilliButz",
+        "repo": "preservation",
+        "type": "github"
+      }
+    },
     "rebmit": {
       "inputs": {
         "devshell": "devshell",
@@ -449,7 +449,6 @@
           "git-hooks-nix"
         ],
         "home-manager": "home-manager",
-        "impermanence": "impermanence",
         "lanzaboote": "lanzaboote",
         "niri-flake": "niri-flake",
         "nixpkgs": [
@@ -461,6 +460,7 @@
           "rebmit",
           "nixpkgs-unstable"
         ],
+        "preservation": "preservation",
         "rebmit": "rebmit",
         "sops-nix": "sops-nix",
         "treefmt-nix": [

flake.nix

@@ -31,7 +31,7 @@
 
     # nixos modules
 
-    impermanence.url = "github:nix-community/impermanence";
+    preservation.url = "github:WilliButz/preservation";
     home-manager = {
       url = "github:nix-community/home-manager";
       inputs.nixpkgs.follows = "nixpkgs";

flake/home-manager.nix

@@ -18,6 +18,7 @@ let
         applications.base
         fish
         helix
+        preservation
         tmux
         yazi
         # keep-sorted end

flake/hosts.nix

@@ -49,7 +49,7 @@ let
     name:
     nixosModules
     ++ [
-      inputs.impermanence.nixosModules.impermanence
+      inputs.preservation.nixosModules.preservation
       inputs.home-manager.nixosModules.home-manager
       inputs.sops-nix.nixosModules.sops
       inputs.disko.nixosModules.disko

flake/nixos.nix

@@ -28,11 +28,11 @@ let
         system.boot.kernel.latest
         system.boot.systemd-initrd
         system.common
-        system.global-persistence
         system.nix.gc
         system.nix.registry
         system.nix.settings
         system.nix.version
+        system.preservation
         users.root
         # keep-sorted end
       ];

home-manager/modules/home/global-persistence.nix

@@ -1,53 +0,0 @@
-# Portions of this file are sourced from
-# https://github.com/linyinfeng/dotfiles/blob/b618b0fd16fb9c79ab7199ed51c4c0f98a392cea/home-manager/modules/home/global-persistence.nix
-{
-  config,
-  lib,
-  osConfig,
-  ...
-}:
-with lib;
-let
-  cfg = config.home.globalPersistence;
-  sysCfg = osConfig.environment.globalPersistence;
-in
-{
-  options.home.globalPersistence = {
-    enable = mkEnableOption "global presistence storage";
-    home = mkOption {
-      type = types.str;
-      description = ''
-        Home directory.
-      '';
-    };
-    directories = mkOption {
-      type = with types; listOf str;
-      default = [ ];
-      description = ''
-        A list of directories in your home directory that you want to link to persistent storage.
-      '';
-    };
-    files = mkOption {
-      type = with types; listOf str;
-      default = [ ];
-      description = ''
-        A list of files in your home directory you want to link to persistent storage.
-      '';
-    };
-    enabled = mkOption {
-      type = types.bool;
-      default = false;
-      description = ''
-        Is global home persistence storage enabled.
-      '';
-    };
-  };
-
-  config = mkIf (osConfig != null && sysCfg.enable) {
-    home.globalPersistence = {
-      inherit (sysCfg.user) directories;
-      inherit (sysCfg.user) files;
-      enabled = cfg.enable;
-    };
-  };
-}

home-manager/modules/preservation.nix

@@ -0,0 +1,57 @@
+{
+  config,
+  lib,
+  osConfig,
+  ...
+}:
+with lib;
+let
+  cfg = config.preservation;
+  sysCfg = osConfig.preservation;
+in
+{
+  options.preservation = {
+    enable = mkEnableOption "the preservation module";
+    preserveAt = mkOption {
+      type = types.attrsOf (
+        types.submodule (
+          { ... }:
+          {
+            options = {
+              directories = mkOption {
+                type = with types; listOf (coercedTo str (d: { directory = d; }) anything);
+                default = [ ];
+                description = ''
+                  Specify a list of directories that should be preserved for this user.
+                  The paths are interpreted relative to the user's home directory.
+                '';
+              };
+              files = mkOption {
+                type = with types; listOf (coercedTo str (f: { file = f; }) anything);
+                default = [ ];
+                description = ''
+                  Specify a list of files that should be preserved for this user.
+                  The paths are interpreted relative to the user's home directory.
+                '';
+              };
+            };
+          }
+        )
+      );
+      default = { };
+      description = ''
+        Specify a set of locations and the corresponding state that
+        should be preserved for this user.
+      '';
+    };
+  };
+
+  config = {
+    warnings = mkIf (cfg.enable && !sysCfg.enable) [
+      ''
+        The preservation module is enabled in Home Manager but disabled system-wide.
+        As a result, the settings will not take effect.
+      ''
+    ];
+  };
+}

home-manager/profiles/applications/desktop.nix

@@ -17,7 +17,7 @@
     # keep-sorted end
   ];
 
-  home.globalPersistence.directories = [
+  preservation.preserveAt."/persist".directories = [
     ".thunderbird"
     ".zotero"
 

home-manager/profiles/darkman/default.nix

@@ -10,7 +10,7 @@ in
 {
   services.darkman.enable = true;
 
-  home.globalPersistence.directories = [ ".cache/darkman" ];
+  preservation.preserveAt."/persist".directories = [ ".cache/darkman" ];
 
   systemd.user.tmpfiles.rules = [
     "C %h/.cache/darkman/mode.txt - - - - ${defaultMode}"

home-manager/profiles/development/default.nix

@@ -1,6 +1,4 @@
 { ... }:
 {
-  home.globalPersistence.directories = [
-    "Projects"
-  ];
+  preservation.preserveAt."/persist".directories = [ "Projects" ];
 }

home-manager/profiles/direnv/default.nix

@@ -5,5 +5,5 @@
     nix-direnv.enable = true;
   };
 
-  home.globalPersistence.directories = [ ".local/share/direnv" ];
+  preservation.preserveAt."/persist".directories = [ ".local/share/direnv" ];
 }

home-manager/profiles/firefox/default.nix

@@ -178,7 +178,7 @@
     };
   };
 
-  home.globalPersistence.directories = [ ".mozilla" ];
+  preservation.preserveAt."/persist".directories = [ ".mozilla" ];
 
   programs.niri.browser = lib.mkDefault [ "firefox" ];
 }

home-manager/profiles/fish/default.nix

@@ -39,5 +39,5 @@
     '';
   };
 
-  home.globalPersistence.directories = [ ".local/share/fish" ];
+  preservation.preserveAt."/persist".directories = [ ".local/share/fish" ];
 }

home-manager/profiles/preservation/default.nix

@@ -0,0 +1,17 @@
+{ lib, osConfig, ... }:
+{
+  preservation = {
+    enable = true;
+    preserveAt."/persist" = {
+      directories =
+        [
+          ".cache/nix"
+          ".local/share/nix"
+          ".ssh"
+        ]
+        ++ lib.optionals osConfig.services.gnome.gnome-keyring.enable [
+          ".local/share/keyrings"
+        ];
+    };
+  };
+}

home-manager/profiles/syncthing/default.nix

@@ -2,5 +2,5 @@
 {
   services.syncthing.enable = true;
 
-  home.globalPersistence.directories = [ ".local/state/syncthing" ];
+  preservation.preserveAt."/persist".directories = [ ".local/state/syncthing" ];
 }

home-manager/profiles/valent/default.nix

@@ -15,7 +15,5 @@
     Install.WantedBy = [ "graphical-session.target" ];
   };
 
-  home.globalPersistence.directories = [
-    ".config/valent"
-  ];
+  preservation.preserveAt."/persist".directories = [ ".config/valent" ];
 }

home-manager/profiles/xdg-user-dirs/default.nix

@@ -13,7 +13,7 @@
     videos = "$HOME/Videos";
   };
 
-  home.globalPersistence.directories = [
+  preservation.preserveAt."/persist".directories = [
     "Documents"
     "Downloads"
     "Music"

nixos/modules/system/global-persistence.nix

@@ -1,79 +0,0 @@
-# Portions of this file are sourced from
-# https://github.com/linyinfeng/dotfiles/blob/b618b0fd16fb9c79ab7199ed51c4c0f98a392cea/nixos/modules/environment/global-persistence/default.nix
-{
-  config,
-  lib,
-  ...
-}:
-let
-  cfg = config.environment.globalPersistence;
-  userCfg =
-    name:
-    assert config.home-manager.users.${name}.home.globalPersistence.enabled;
-    {
-      inherit name;
-      value = {
-        inherit (config.home-manager.users.${name}.home.globalPersistence) home directories files;
-      };
-    };
-  usersCfg = lib.listToAttrs (map userCfg cfg.user.users);
-in
-with lib;
-{
-  options.environment.globalPersistence = {
-    enable = mkEnableOption "global persistence storage";
-    root = mkOption {
-      type = types.str;
-      description = ''
-        The root of persistence storage.
-      '';
-    };
-    directories = mkOption {
-      type = with types; listOf str;
-      default = [ ];
-      description = ''
-        Directories to bind mount to persistent storage.
-      '';
-    };
-    files = mkOption {
-      type = with types; listOf str;
-      default = [ ];
-      description = ''
-        Files that should be stored in persistent storage.
-      '';
-    };
-    user = {
-      users = mkOption {
-        type = with types; listOf str;
-        default = [ ];
-        description = ''
-          Persistence for users.
-        '';
-      };
-      directories = mkOption {
-        type = with types; listOf str;
-        default = [ ];
-        description = ''
-          Directories to bind mount to persistent storage for users.
-          Paths should be relative to home of user.
-        '';
-      };
-      files = mkOption {
-        type = with types; listOf str;
-        default = [ ];
-        description = ''
-          Files to link to persistent storage for users.
-          Paths should be relative to home of user.
-        '';
-      };
-    };
-  };
-
-  config = mkIf cfg.enable {
-    environment.persistence."${cfg.root}" = {
-      hideMounts = true;
-      inherit (cfg) directories files;
-      users = usersCfg;
-    };
-  };
-}

nixos/profiles/services/gnome-keyring/default.nix

@@ -1,6 +1,4 @@
 { ... }:
 {
   services.gnome.gnome-keyring.enable = true;
-
-  environment.globalPersistence.user.directories = [ ".local/share/keyrings" ];
 }

nixos/profiles/services/openssh/default.nix

@@ -90,6 +90,4 @@ in
     };
     restartUnits = [ "sshd.service" ];
   };
-
-  environment.globalPersistence.user.directories = [ ".ssh" ];
 }

nixos/profiles/system/boot/secure-boot.nix

@@ -9,5 +9,5 @@
     pkiBundle = "/etc/secureboot";
   };
 
-  environment.globalPersistence.directories = [ "/etc/secureboot" ];
+  preservation.preserveAt."/persist".directories = [ "/etc/secureboot" ];
 }

nixos/profiles/system/global-persistence.nix

@@ -1,27 +0,0 @@
-{ config, ... }:
-{
-  assertions = [
-    {
-      assertion = config.fileSystems ? "/persist";
-      message = ''
-        `config.fileSystems."/persist"` must be set.
-      '';
-    }
-  ];
-
-  environment.globalPersistence = {
-    enable = true;
-    root = "/persist";
-    directories = [
-      "/var/cache"
-      "/var/lib"
-      "/var/log"
-      "/var/tmp"
-    ];
-    files = [
-      "/etc/machine-id"
-    ];
-  };
-
-  systemd.suppressedSystemUnits = [ "systemd-machine-id-commit.service" ];
-}

nixos/profiles/system/nix/settings.nix

@@ -20,9 +20,4 @@
       builders-use-substitutes = true;
     };
   };
-
-  environment.globalPersistence.user.directories = [
-    ".cache/nix"
-    ".local/share/nix"
-  ];
 }

nixos/profiles/system/preservation.nix

@@ -0,0 +1,94 @@
+{ config, lib, ... }:
+{
+  assertions = [
+    {
+      assertion = config.fileSystems ? "/persist";
+      message = ''
+        `config.fileSystems."/persist"` must be set.
+      '';
+    }
+  ];
+
+  preservation = {
+    enable = true;
+    preserveAt = lib.mkMerge (
+      lib.mapAttrsToList (
+        name: hmCfg:
+        lib.mapAttrs (_: preserve: {
+          users.${name} = {
+            home = hmCfg.home.homeDirectory;
+            inherit (preserve) directories files;
+          };
+        }) hmCfg.preservation.preserveAt
+      ) (lib.filterAttrs (_: hmCfg: hmCfg.preservation.enable) config.home-manager.users)
+      ++ lib.singleton {
+        "/persist" = {
+          directories = [
+            {
+              directory = "/var/cache";
+              inInitrd = true;
+            }
+            {
+              directory = "/var/lib";
+              inInitrd = true;
+            }
+            {
+              directory = "/var/log";
+              inInitrd = true;
+            }
+            {
+              directory = "/var/tmp";
+              inInitrd = true;
+            }
+          ];
+          files = [
+            {
+              file = "/etc/machine-id";
+              inInitrd = true;
+              how = "symlink";
+              configureParent = true;
+            }
+          ];
+        };
+      }
+    );
+  };
+
+  # https://github.com/NixOS/nixpkgs/pull/351151#issuecomment-2549025171
+  systemd.services.systemd-machine-id-commit = {
+    unitConfig.ConditionPathIsMountPoint = [
+      ""
+      "/persist/etc/machine-id"
+    ];
+    serviceConfig.ExecStart = [
+      ""
+      "systemd-machine-id-setup --commit --root /persist"
+    ];
+  };
+
+  # https://willibutz.github.io/preservation/examples.html
+  systemd.tmpfiles.settings.preservation = lib.mkMerge (
+    lib.mapAttrsToList (name: hmCfg: {
+      "${hmCfg.home.homeDirectory}/.config".d = {
+        user = name;
+        group = config.users.users.${name}.group;
+        mode = "0755";
+      };
+      "${hmCfg.home.homeDirectory}/.local".d = {
+        user = name;
+        group = config.users.users.${name}.group;
+        mode = "0755";
+      };
+      "${hmCfg.home.homeDirectory}/.local/share".d = {
+        user = name;
+        group = config.users.users.${name}.group;
+        mode = "0755";
+      };
+      "${hmCfg.home.homeDirectory}/.local/state".d = {
+        user = name;
+        group = config.users.users.${name}.group;
+        mode = "0755";
+      };
+    }) (lib.filterAttrs (_: hmCfg: hmCfg.preservation.enable) config.home-manager.users)
+  );
+}

nixos/profiles/users/rebmit/default.nix

@@ -34,16 +34,9 @@ in
     sopsFile = config.sops.secretFiles.get "local.yaml";
   };
 
-  environment.globalPersistence.user.users = [ "rebmit" ];
-
   home-manager.users.rebmit =
     { ... }:
     {
-      home.globalPersistence = {
-        enable = true;
-        home = homeDirectory;
-      };
-
       programs.git = {
         userName = "Lu Wang";
         userEmail = "rebmit@rebmit.moe";

nixos/profiles/virtualization/libvirtd/default.nix

@@ -7,6 +7,4 @@
       swtpm.enable = true;
     };
   };
-
-  environment.globalPersistence.user.directories = [ ".config/libvirt" ];
 }