Large refactor

README.org

@@ -21,60 +21,41 @@
     };
   };
 
-  outputs = { nixpkgs, ... }@inputs: {
+  outputs = { nixpkgs, ... }@inputs:
-    nixosConfigurations = (
+    let list-nix-directory = dir:
-      <<flake-outputs-nixos>>
+          builtins.attrNames
-    );
+            (nixpkgs.lib.filterAttrs
-  };
+              (k: _v: nixpkgs.lib.hasSuffix ".nix" k)
-}
+              (builtins.readDir dir));
-#+end_src
+    in {
+      # REVIEW: Why don't we put each module under nixosModules.<name>?
+      nixosModules.default =
+        let modules = list-nix-directory ./modules/nixos;
+        in { ... }: {
+          imports =
+            let x = builtins.map (m: ./modules/nixos/${m}) modules;
+                in x;
+        };
 
-* Features
+      homeManagerModules.default =
+        let modules = list-nix-directory ./modules/home;
+        in { ... }: {
+          imports = builtins.map (m: ./modules/home/${m}) modules;
+        };
 
-What are referred to as /features/ here largely correspond to Nix modules, but are
+      nixosConfigurations = (
-not limited to Nix modules.
+        <<flake-outputs-nixos>>
+      );
 
-** Impermanence
+      homeConfigurations =
-
+        let users = builtins.readDir ./users;
-*** Flake input
+            mkUser = username: _v: import ./users/${username}/default.nix;
-
+        in
-#+begin_src nix :noweb-ref flake-inputs
+          builtins.mapAttrs mkUser users;
-impermanence.url = "github:nix-community/impermanence";
-#+end_src
-
-*** Top-level module
-
-#+begin_src nix :tangle modules/system/impermanence.nix
-{ config, lib, pkgs, ... }:
-
-with lib;
-
-let
-  cfg = config.sydnix.impermanence;
-in {
-  options = {
-    sydnix.impermanence = {
-      <<sydnix-impermanence-options>>
     };
-  };
-
-  config = mkIf cfg.enable (mkMerge [
-
-  ]);
 }
 #+end_src
 
-*** Options
-
-**** =enable=
-
-#+begin_src nix :noweb-ref sydnix-impermanence-options
-enable = mkOption {
-  type = types.bool;
-  default = false;
-};
-#+end_src
-
 * Machines
 
 For every ~./hosts/NAME/configuration.nix~, define the system under the name ~NAME~.
@@ -85,8 +66,25 @@ let mkHost = k: v: nixpkgs.lib.nixosSystem {
       system = import ./hosts/${k}/system.nix;
       modules = [
         ./hosts/${k}/configuration.nix
+
+        inputs.self.nixosModules.default
+
+        inputs.disko.nixosModules.disko
+
         # Directory name should always match host name.
         ({ ... }: { networking.hostName = k; })
+
+        # home-manager configuration.
+        inputs.home-manager.nixosModules.home-manager
+        ({ config, lib, self, ... }: {
+          home-manager.useGlobalPkgs = true;
+          home-manager.useUserPackages = true;
+
+          home-manager.users =
+            lib.filterAttrs
+              (k: _v: builtins.elem k config.sydnix.users.users)
+              self.homeConfigurations;
+        })
       ];
     };
 in
@@ -101,94 +99,31 @@ builtins.mapAttrs mkHost (builtins.readDir ./hosts)
   imports = [
     ./hardware-configuration.nix
     ./disko-config.nix
-    disko.nixosModules.disko
   ];
 
-  # boot.initrd.postDeviceCommands = ''
+  sydnix = {
-  #   if zfs list -t snapshot -H -o name \
+    users.users = [
-  #       | grep -qE '^rpool/local/root@previous$'; then
+      "crumb"
-  #     zfs destroy -r rpool/local/root@previous \
-  #     && echo ">> >> previous previous snapshot destroyed << <<"
-  #   else
-  #     echo ">> >> no previous previous snapshot found << <<"
-  #   fi
-
-  #   zfs snapshot -r rpool/local/root@previous \
-  #     && echo ">> >> pre-rollback snapshot taken << <<"
-
-  #   zfs rollback -r rpool/local/root@blank \
-  #     && echo ">> >> rollback complete << <<"
-  # '';
-
-  # boot.initrd.supportedFilesystems = [ "zfs" ];
-  # boot.supportedFilesystems = [ "zfs" ];
-
-  boot.initrd.enable = true;
-  boot.initrd.systemd.enable = true;
-
-  boot.initrd.systemd.initrdBin = with pkgs; [
-    zfs
-    coreutils
-    babashka
-  ];
-
-  boot.initrd.systemd.services.erase-darlings = {
-    description = "Rollback filesystem to a blank state on boot";
-    wantedBy = [
-      "initrd.target"
     ];
-    after = [
-      # "zfs-import.service"
-      "zfs-import-rpool.service"
-    ];
-    before = [
-      "sysroot.mount"
-    ];
-    path = [ pkgs.zfs ];
-    unitConfig.DefaultDependencies = "no";
-    serviceConfig = {
-      Type = "oneshot";
-      RemainAfterExit = true;
-    };
-    script = /* bash */ ''
-      zfs rollback -r rpool/local/root@blank \
-        && echo ">> >> rollback complete << <<"
-    '';
   };
 
-  systemd.services.erase-home-darlings = {
+  boot = {
-    description = "Rollback home to a blank state on boot";
+    initrd = {
-    wantedBy = [
+      enable = true;
-      "multi-user.target"
+      systemd.enable = true;
-    ];
-    before = [
-      # "basic.target"
-    ];
-    after = [
-      "home.mount"
-    ];
-    path = [ pkgs.zfs pkgs.babashka ];
-    # unitConfig.DefaultDependencies = "no";
-    serviceConfig = {
-      Type = "oneshot";
-      RemainAfterExit = true;
-      ExecStart =
-        let script = ./erase-home-darlings.clj;
-        in ''${pkgs.babashka}/bin/bb "${script}" 3'';
-    };
-    stopIfChanged = false;
-    restartIfChanged = false;
-  };
 
-  # boot.loader.grub = {
+      systemd.initrdBin = with pkgs; [
-  #   enable = true;
+        zfs
-  #   device = "nodev";
+        coreutils
-  #   # device = "/dev/vda";
+        babashka
-  #   efiSupport = true;
+      ];
-  #   efiInstallAsRemovable = true;
+    };
-  # };
+
-  boot.loader.systemd-boot.enable = true;
+    loader = {
-  boot.loader.efi.canTouchEfiVariables = false;
+      systemd-boot.enable = true;
+      efi.canTouchEfiVariables = false;
+    };
+  };
 
   # networking.hostName = "nixos-testbed";
   networking.hostId = "238e9b1e"; # head -c 8 /etc/machine-id
@@ -196,6 +131,7 @@ builtins.mapAttrs mkHost (builtins.readDir ./hosts)
   time.timeZone = "America/Denver";
 
   i18n.defaultLocale = "en_US.UTF-8";
+
   console = {
     font = "Lat2-Terminus16";
     # keyMap = "us";

hosts/nixos-testbed/disko-config.nix

@@ -2,7 +2,7 @@
 # time sudo nixos-install --flake /nixos#nixos-testbed
 { lib, ... }:
 {
-  # imports = [ inputs.disko.nixosModules.disko ];
+  # imports = [ disko.nixosModules.disko ];
   boot.zfs.extraPools = [ "rpool" ];
   boot.zfs.devNodes = "/dev/disk/by-path";
   boot.initrd.supportedFilesystems = [ "zfs" ];
@@ -18,8 +18,6 @@
           partitions = {
             ESP = {
               size = "512M";
-              # start = "1MiB";
-              # end = "512M";
               type = "EF00";
               content = {
                 type = "filesystem";
@@ -29,8 +27,6 @@
               };
             };
             root = {
-              # start = "512M";
-              # end = "100%";
               size = "100%";
               content = {
                 type = "zfs";
@@ -44,23 +40,6 @@
     zpool = {
       rpool = {
         type = "zpool";
-
-        # Workaround: cannot import 'rpool': I/O error in disko tests
-        # options.cachefile = "none";
-
-        # rootFsOptions = {
-        #   # I don't know.
-        #   # https://wiki.archlinux.org/title/Systemd#systemd-tmpfiles-setup.service_fails_to_start_at_boot
-        #   acltype = "posixacl";
-        #   # atime = "off";
-        #   # compression = "zstd";
-        #   mountpoint = "none";
-        #   # xattr = "sa";
-        #   "com.sun:auto-snapshot" = "false";
-        # };
-
-        # mountpoint = "/";
-
         datasets =
           let dataset = options:
                 let default = {
@@ -97,59 +76,16 @@
               mountpoint = "/persist/home";
             };
             "reserved" = dataset {
-              mountpoint = null;
               options = {
                 canmount = "off";
                 mountpoint = "none";
                 reservation = "5GiB";
               };
             };
-          # "local" = {
-          #   type = "zfs_fs";
-          #   options.mountpoint = "none";
-          # };
-          # "safe" = {
-          #   type = "zfs_fs";
-          #   options.mountpoint = "none";
-          # };
-          # "local/root" = {
-          #   type = "zfs_fs";
-          #   options.mountpoint = "legacy";
-          #   mountpoint = "/";
-          #   options."com.sun:auto-snapshot" = "false";
-          #   postCreateHook = ''
-          #     zfs list -t snapshot -H -o name \
-          #       | grep -E '^rpool/local/root@blank$' \
-          #       || zfs snapshot rpool/local/root@blank
-          #   '';
-          # };
-          # "local/home" = {
-
-          # };
-          # "local/nix" = {
-          #   type = "zfs_fs";
-          #   options.mountpoint = "legacy";
-          #   mountpoint = "/nix";
-          #   options."com.sun:auto-snapshot" = "false";
-          # };
-          # "safe/persist" = {
-          #   type = "zfs_fs";
-          #   options.mountpoint = "legacy";
-          #   mountpoint = "/persist";
-          #   options."com.sun:auto-snapshot" = "false";
-          # };
-          #  # zfs uses copy on write and requires some free space to delete files when the disk is completely filled
-          # "reserved" = lib.recursiveUpdate (dataset "reserved") {
-          #   mountpoint = null;
-          #   options = {
-          #     canmount = "off";
-          #     mountpoint = "none";
-          #     reservation = "5GiB";
-          #   };
-          #   type = "zfs_fs";
-          # };
         };
       };
     };
   };
+
+  fileSystems."/persist".neededForBoot = true;
 }

modules/home/erase-home-darlings.clj

@@ -0,0 +1,84 @@
+#!/usr/bin/env bb
+
+;;; TODO: option to either move OR copy
+
+(require '[clojure.core.match :refer [match]]
+         '[babashka.cli :as cli]
+         '[babashka.process :refer [$ check] :as p])
+
+(defn get-archive-path []
+  (fs/path
+   "/persist/previous"))
+
+(defn get-files []
+  (let [diff (:out (check ($ {:out :string}
+                             "zfs" "diff" "-HF"
+                             "rpool/local/home@blank"
+                             "rpool/local/home")))]
+    ;; See zfs-diff(8) to understand what we're parsing here.
+    (->> diff
+         str/split-lines
+         (map #(str/split % #"\s"))
+         (filter #(and
+                   ;; We only care to preserve /new/ content.
+                   (contains? #{"+" "M"} (first %))
+                   ;; We only bother with plain old files.  No directories,
+                   ;; symlinks, etc.
+                   (= (second %) "F")))
+         (map #(nth % 2)))))
+
+(defn move-out-of-my-way [file]
+  ;; No TCO. }:<
+  (loop [n 0]
+    (let [file' (format "%s-%d" file n)]
+      (if (fs/exists? file')
+        (recur (inc n))
+        (do (fs/move file file')
+            file')))))
+
+(defn archive-files [archive-path files]
+  (let [new-archive (fs/path archive-path "home/new-archive")]
+    (when (fs/exists? new-archive)
+      (println "Warning: `new-archive' already exists... we'll rename it for you?")
+      (move-out-of-my-way new-archive))
+    (doseq [file files]
+      (let [destination (fs/path
+                         new-archive
+                         (fs/relativize "/home" (fs/parent file)))]
+        (fs/create-dirs destination)
+        (fs/move file destination)))))
+
+(defn cycle-archives [archive-path n]
+  "Delete the oldest archive path, and increment each previous path by one.
+More precisely,
+ - Delete the archive path labeled `n` (the oldest allowed).
+ - For each remaining path labeled 'i', relabel to 'i + 1'.
+ - Lastly, we delete the path labeled `new-archive`, if it exists."
+  (let [gp #(fs/path archive-path "home" (str %))]
+    (fs/delete-if-exists (gp n))
+    (doseq [i (range (dec n) 1 -1)]
+      (when (fs/exists? (gp (dec i)))
+        (fs/move (gp (dec i)) (gp i))))
+    (when (fs/exists? (gp "new-archive"))
+      (fs/move (gp "new-archive") (gp 1)))))
+
+(defn do-rollback []
+  (let [proc (deref ($ "zfs" "rollback" "-r" "rpool/local/home@blank"))]
+    (if (= (:exit proc) 0)
+      (println (str "Successfully rolled back /home.  "
+                    "Enjoy the fresh filesystem smell!  }:D"))
+      (println "Something went wrong rolling back /home... D:{"))))
+
+(defn -main []
+  (let [n (if (< 0 (count *command-line-args*))
+            (parse-long (first *command-line-args*))
+            3)]
+    (binding [p/*defaults*
+              {:pre-start-fn #(println (str "+ " (str/join (:cmd %))))}]
+      (let [archive-path (get-archive-path)
+            files (get-files)]
+        (archive-files archive-path files)
+        (cycle-archives archive-path n)
+        (do-rollback)))))
+
+(-main)

modules/nixos/users.nix

@@ -0,0 +1,18 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.sydnix.users;
+in {
+  options = {
+    sydnix.users = {
+      users = mkOption {
+        description =
+          "List of usernames whose home profiles should be imported.";
+        type = with types; listOf str;
+        default = [];
+      };
+    };
+  };
+}

users/crumb/default.nix

@@ -0,0 +1,6 @@
+{ config, lib, pkgs, ... }:
+
+{
+  home.stateVersion = "18.09";
+  home.packages = [ pkgs.hello ];
+}