refactor

README.md

@@ -59,20 +59,13 @@ And... that's basically all you need.
 
 ### A NixOS builder with local cache
 
-The nix builder will create a local cache on your node agent at `/var/cache/albatros`.
-It will create two folders: `/var/cache/albatros/nix` that contains a nix store,
-and `/var/cache/albatros/cacheroot` that contains nix roots, ie. the builds we must keep.
-
-Caching is handled thanks to these roots: roots that are older than 7 days will be removed,
-then a garbage collection will be triggered, and their associate content will be deleted.
-
-To keep your cache between builds, you must put your outlink in `/mnt/cacheroot` with a unique name.
-The git commit is a good candidate:
-
-```bash
-# create an output link at a persisted path
-nix build --out-link $GCROOT
-```
+In the `hcl/` folder, you will find the definition of a builder named `nixcache`.
+This builder has the following features:
+  - It creates a persisted nix store at `/var/cache/albatros` on your host if it does not exist yet.
+  - The nix store is mounted read-only during the build
+  - A nix daemon is run in a separate container, you can interact with it though its unix socket (everything is already setup for you). Simply run `nix build`.
+  - All your builds are automatically added as a nix gcroots by the nix daemon, `keep_derivation` is activated so your build dependencies are kept locally.
+  - At the end, all gcroots older than 7 days are deleted, and then the `nix store gc` is called effectively wiping data that were previously attached to old gcroots.
 
 ## Register a build