Add docker module

modules/docker/default.nix

@@ -0,0 +1,46 @@
+{
+  config,
+  lib,
+  ...
+}:
+with lib; let
+  cfg = config.flock.docker;
+in {
+  options = {
+    flock.docker = {
+      enable = mkEnableOption "Enable Docker";
+      dockerMount = mkEnableOption "Mount disk as Docker directory";
+    };
+  };
+
+  config =
+    mkIf cfg.enable
+    {
+      # Add user to docker group.
+      users.users.fern = {
+        extraGroups = ["docker"];
+      };
+
+      # Enable docker.
+      virtualisation.docker = {
+        enable = true;
+        autoPrune.enable = true;
+        liveRestore = true;
+        daemon.settings = {
+          data-root = "/home/fern/docker/daemon";
+          default-address-pools = [
+            {
+              base = "172.20.0.0/12";
+              size = 24;
+            }
+          ];
+        };
+      };
+
+      # Docker data directory
+      fileSystems."/home/fern/docker" = mkIf (cfg.dockerMount) {
+        device = "/dev/disk/by-label/docker";
+        fsType = "ext4";
+      };
+    };
+}