DOC: update README_SETUP; mention logout after usermod

README_SETUP.md

@@ -12,11 +12,13 @@ sudo apt-get install docker.io docker-compose
 ```
 
 Note, that your user account needs to be in the docker group to start a
-container:
+container. Security note: The docker group is equivalent to root permissions.
 
 ```sh
 sudo usermod -aG docker $USER
 ```
+You should log out after this step and log in again. You can check with the
+command `groups` whether you have the docker group.
 
 It is recommended that you clone this repository such that you have the
 example configuration files at hand.
@@ -42,6 +44,9 @@ caosdb-server_1  | Starting org.caosdb.server.CaosDBServer application
 ```
 
 the server is ready and you can access CaosDB with your web browser under `localhost:8081`.
+Default credentials are
+- username: `admin`
+- password: `caosdb`
 
 ## Stopping CaosDB ##
 You can stop the containers with CTRL-C. See the documentation of docker-compose