Flakes: Difference between revisions

@@ Line 299: / Line 299: @@
    };
 </syntaxHighlight>
+{{warning|The above example seems to break nix's eval cache, and may slow down hdd systems significantly!}}
+To make sure the registry entry is "locked", use the following:
+<syntaxHighlight lang=nix>
+  nix.registry = {
+    nixpkgs.to = {
+      type = "path";
+      path = pkgs.path;
+      narHash = builtins.readFile
+          (pkgs.runCommandLocal "get-nixpkgs-hash"
+            { nativeBuildInputs = [ pkgs.nix ]; }
+            "nix-hash --type sha256 --sri ${pkgs.path} > $out");
+    };
+  };
+</syntaxHighlight>
+This has the unfortunate side-effect of requiring import-from-derivation and slowing down build times, however it may greatly speed up almost every eval. Full-time flakes users may be able to just use <code>narHash = pkgs.narHash</code>.
 == Super fast nix-shell ==