run as prometheus user insted of root

Dockerfile

@@ -7,12 +7,17 @@ COPY documentation/examples/prometheus.yml  /etc/prometheus/prometheus.yml
 COPY console_libraries/                     /usr/share/prometheus/console_libraries/
 COPY consoles/                              /usr/share/prometheus/consoles/
 
-RUN ln -s /usr/share/prometheus/console_libraries /usr/share/prometheus/consoles/ /etc/prometheus/
+RUN ln -s /usr/share/prometheus/console_libraries /usr/share/prometheus/consoles/ /etc/prometheus/ && \
+    addgroup -g 1000 prometheus && \
+    adduser -s /bin/sh -S -H -u 1000 -G prometheus prometheus && \
+    mkdir -p /prometheus && \
+    chown -R prometheus:prometheus /etc/prometheus /prometheus
 
 EXPOSE     9090
 VOLUME     [ "/prometheus" ]
 WORKDIR    /prometheus
 ENTRYPOINT [ "/bin/prometheus" ]
+USER       prometheus
 CMD        [ "-config.file=/etc/prometheus/prometheus.yml", \
              "-storage.local.path=/prometheus", \
              "-web.console.libraries=/usr/share/prometheus/console_libraries", \