Limit envsub to only variable being changed

Author: antonym

root/init.sh

@@ -14,7 +14,7 @@ mkdir -p \
 [[ ! -f /config/nginx/nginx.conf ]] &&
   cp /defaults/nginx.conf /config/nginx/nginx.conf
 [[ ! -f /config/nginx/site-confs/default ]] &&
-  envsubst </defaults/default >/config/nginx/site-confs/default
+  envsubst '${NGINX_PORT}' < /defaults/default > /config/nginx/site-confs/default
 
 # create dnsmasq config, and conditionally add DHCP proxy support
 if [[ ! -f /config/dnsmasq/dnsmasq.conf ]]; then