From 3ef8c5309e5da4a6ee2ece3d87aa3767985d40d5 Mon Sep 17 00:00:00 2001
From: deveth0 <github@dev-eth0.de>
Date: Tue, 5 Mar 2019 13:05:27 +0100
Subject: [PATCH] #197: Enable envsubst - README

---
 README.md | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/README.md b/README.md
index b2f4889..86fc9d1 100644
--- a/README.md
+++ b/README.md
@@ -182,6 +182,31 @@ Create file `config/server-adminlist.json` and add the adminlisted users.
         "friend"
     ]
 
+## Customize configuration files
+
+Out-of-the box, factorio does not support environment variables inside the configuration files. A workaround is the usage of `envsubst` which generates the configuration files dynamically during startup.
+
+Example for server-settings.json:
+
+
+	factorio_1:
+	  image: dtanders/factorio
+	  ports:
+	    - "34197:34197/udp"
+	  volumes:
+	   - /opt/factorio:/factorio
+	   - ./server-settings.json:/server-settings.json
+	  environment:
+	    - INSTANCE_NAME=Your Instance's Name
+	    - INSTANCE_DESC=Your Instance's Description
+	  entrypoint: /bin/sh -c "envsubst < /server-settings.json > /factorio/config/server-settings.json && exec /docker-entrypoint.sh"
+
+The `server-settings.json` file may then contain the variable references like this:
+
+	"name": "${INSTANCE_NAME}",
+	"description": "${INSTANCE_DESC}",
+
+
 # Container Details
 
 The philosophy is to [keep it simple](http://wiki.c2.com/?KeepItSimple).