DOC: add a hint how to provide a readable certificate

README_SETUP.md

@@ -5,7 +5,7 @@ We use docker and docker-compose to deploy CaosDB:
 - Docker >= 18.02
 - docker-compose >= 1.21
 
-On a Debian system, you can install the requirements with:
+On Debian based systems, you can install the requirements with:
 
 ```sh
 sudo apt-get install docker.io docker-compose
@@ -91,6 +91,8 @@ one with `openssl rsa -in oldKey.pem -out newKey.key`. If you want to use a
 certificate with a passphrase instead, please refer to envoy's documentation as
 to how to configure this correctly.
 
+Make sure that envoy can read the certificate. You can set the UID for envoy in
+the environment section of the envoy service in `docker-compose.yml`.
 
 ## Configuration
 

compose/docker-compose.yml

@@ -51,6 +51,8 @@ services:
 
   envoy:
     image: envoyproxy/envoy:v1.21-latest
+    # environment:
+    #   ENVOY_UID: 987
     volumes:
       - type: bind
         read_only: true