Added Dockerfile and docker-compose.yml

Dockerfile

@@ -0,0 +1,37 @@
+FROM alpine:latest
+MAINTAINER Christian Baer <chris@debilux.org>
+
+ENV TZ "UTC"
+
+## Run cron every minute
+ENV SCHEDULE "* * * * *"
+
+ENV GIT_REPO "https://github.com/chrisb86/nsupdate"
+ENV NSUPDATE_CONFD_DIR="/config"
+ENV NSUPDATE_LOG_DIR="/log"
+
+## Install requirements
+RUN apk update
+RUN apk add --update-cache \
+        git \
+        curl \
+        libxml2-utils
+
+# Read timezone from server, so in docker-compose you can change TZ
+RUN apk add --no-cache tzdata
+
+RUN ln -sf "/usr/share/zoneinfo/$TZ" /etc/localtime && \
+    echo "$TZ" > /etc/timezone && date
+
+## Clone git repo
+RUN mkdir app
+RUN git clone $GIT_REPO /app
+
+## Setup cron job
+RUN echo "${SCHEDULE} sh /app/nsupdate.sh" >> /etc/crontabs/root
+
+## Start crond
+CMD [ "crond", "-l", "2", "-f" ]
+
+VOLUME /config
+VOLUME /log