- Validate the Unbound configuration during the image build.

Dockerfile

@@ -2,7 +2,8 @@ FROM debian:stretch-slim
 ENV DEBIAN_FRONTEND noninteractive
 RUN apt-get update && \
     apt-get install -y unbound unbound-host dnsutils dma bsd-mailx && \
-    rm -rf /tmp/* /var/tmp/* /var/lib/apt/lists/* /var/cache/apt/archives/*
+    rm -rf /tmp/* /var/tmp/* /var/lib/apt/lists/* /var/cache/apt/archives/* &&
+    unbound-checkconf
 COPY entrypoint.sh /entrypoint.sh
 ENTRYPOINT ["/entrypoint.sh"]
 CMD ["/bin/bash", "--login"]