Update README.md

Clarification of docker usage

Author: georgweiss

services/alarm-server/README.md

@@ -50,29 +50,18 @@ some useful startup arguments include
 
 ## Docker
 
-Docker compose files are provided for convenience to cover two use cases:
+Docker compose files are provided to cover two use cases:
 
-1. ```docker-compose-alarm-server-only.yml``` will run the alarm server. Required environment variables:
-    * ```KAFKA_HOST_IP_ADDRESS``` must be set to identify the Kafka server external IP address.
-    * ```CONFIG``` identifies the configuration (topic) name. 
-    * ```ALARM_SERVICE_SETTINGS_FILE``` file in user's home directory specifying EPICS related settings, e.g.
-      ```org.phoebus.pv/default=pva```.
-2. ```docker-compose-alarm-server-only-import.yml``` will run the alarm server for the
-    purpose of importing a configuration. Environment variables must be se as in case 1.
-    Additionally, the environment variable ```CONFIG_FILE``` must identify an alarm
-    configuration file in the current user's home directory.
+1. ```docker-compose-alarm-server-only-import.yml``` will run the alarm server for the
+    purpose of importing a configuration. 
+2. ```docker-compose-alarm-server-only.yml``` will run the alarm server. 
 
-Docker supports environment variables to be set in a file (default ```.env``` in current directory) like so:
+The docker compose files do **not** launch 3rd party services needed by the alarm service. User is advocated to
+consult https://github.com/ControlSystemStudio/phoebus/blob/master/services/README.md for information on how
+to prepare the required environment and alarm service settings files, and how launch these services through docker.
 
-```KAFKA_HOST_IP_ADDRESS=1.2.3.4```  
-```CONFIG=Accelerator```  
-.  
-.  
-.  
+To launch docker, use:
+```>docker compose --env-file <path-to-environment-file> -f docker-compose-alarm-server-only*.yml up```
 
-This may be preferable compared to setting environment variables on command line, e.g. 
-
-```>export KAFKA_HOST_IP_ADDRESS=1.2.3.4```.
-
-**NOTE:** Accessing IOCs over pva (default mode in the Docker compose files) works **only** if IOC is running on the
-same host as the Docker container. Moreover, this has been verified to work only on Linux.
+**NOTE:** Accessing IOCs over pva (default mode in the alarm serv) works **only** if IOC is running on the
+same host as the Docker container. Moreover, this has been verified to work only on Linux.