update container docs

Signed-off-by: Kristoffer Dalby <[email protected]>

docs/running-headscale-container.md

@@ -57,15 +57,22 @@ server_url: http://your-host-name:8080
 # Listen to 0.0.0.0 so it's accessible outside the container
 metrics_listen_addr: 0.0.0.0:9090
 # The default /var/lib/headscale path is not writable in the container
-private_key_path: /etc/headscale/private.key
-# The default /var/lib/headscale path is not writable in the container
 noise:
   private_key_path: /etc/headscale/noise_private.key
+# The default /var/lib/headscale path is not writable in the container
+derp:
+  private_key_path: /etc/headscale/private.key
+# The default /var/run/headscale path is not writable  in the container
+unix_socket: /etc/headscale/headscale.sock
 # The default /var/lib/headscale path is not writable  in the container
 db_type: sqlite3
 db_path: /etc/headscale/db.sqlite
 ```
 
+Alternatively, you can mount `/var/lib` and `/var/run` from your host system by adding
+`--volume $(pwd)/lib:/var/lib/headscale` and `--volume $(pwd)/run:/var/run/headscale`
+in the next step.
+
 4. Start the headscale server while working in the host headscale directory:
 
 ```shell