Optimize docker files

docker/Dockerfile

@@ -0,0 +1,26 @@
+FROM alpine:latest
+
+ENV TZ "UTC"
+ENV SCHEDULE "* * * * *"
+
+## Configure runtime variables for nsupdate
+ENV NSUPDATE_CONFD_DIR="/config"
+ENV NSUPDATE_LOG_DIR="/log"
+
+## Install requirements
+RUN apk update
+RUN apk add --no-cache git curl libxml2-utils tzdata
+
+# Read timezone from server, so in docker-compose you can change TZ
+RUN ln -sf "/usr/share/zoneinfo/${TZ}" /etc/localtime && \
+    echo "${TZ}" > /etc/timezone && date
+
+COPY ../nsupdate.sh /usr/local/bin/nsupdate.sh
+RUN chmod +x /usr/local/bin/nsupdate.sh
+
+COPY docker/entrypoint.sh /
+RUN chmod +x /entrypoint.sh
+ENTRYPOINT ["/entrypoint.sh"]
+
+VOLUME /config
+VOLUME /log