doc
diff --git a/README.md b/README.md
index e1e1c27..d16c145 100644
--- a/README.md
+++ b/README.md
@@ -119,6 +119,8 @@
You can also use data volume containers. Please refer to:
> [https://docs.docker.com/userguide/dockervolumes/](https://docs.docker.com/userguide/dockervolumes/)
+Note: By default this image is waiting an **hdb** database backend, if you want to use any other database backend set backend type via the LDAP_BACKEND environement variable.
+
### Backup
A simple solution to backup your ldap server, is our openldap-backup docker image:
> [osixia/openldap-backup](https://github.com/osixia/docker-openldap-backup)