diff --git a/README.md b/README.md
index 471ff97..27aa337 100644
--- a/README.md
+++ b/README.md
@@ -3,5 +3,6 @@
 ## Commands
 
 ```sh
+export DATA_DIR = /some/path/to/mount
 docker-compose --file software/container/docker-compose.yml up
 ```