DOCKER - Use system’s resolver in dockerized NGINX

NGINX config Template

nginx.conf.tmpl

http {
  server {

    resolver $NAMESERVER valid=10s;

    [...]
    }
  }
}

Docker Entrypoint

Use DNS server from Dockerhost for Container.

Your startup script can then use the envsubst program to generate an nginx.conf and then start nginx. eg:

/entry.sh

#!/bin/bash
if [ "$NAMESERVER" == "" ]; then
	export NAMESERVER=`cat /etc/resolv.conf | grep "nameserver" | awk '{print $2}' | tr '\n' ' '`
fi

echo "Nameserver is: $NAMESERVER"

echo "Copying nginx config"
envsubst '$NAMESERVER' < /nginx.conf.tmpl > /nginx.conf

echo "Using nginx config:"
cat /nginx.conf

echo "Starting nginx"
nginx -c /nginx.conf -g "daemon off;"

Links

• https://web.archive.org/web/20181006183603/https://trac.nginx.org/nginx/ticket/658