Don't run docker container as root

[der-eismann]

IMHO it is accepted as best practice to not run processes in containers as root. It is a problem that is affecting many of prometheus' exporters and I'm not sure if this was discussed before.
It can be fixed pretty easily by adding two lines to the Dockerfile:

RUN adduser -D statsd-exporter
USER statsd-exporter

[SuperQ]

We typically use nobody for our containers.

[der-eismann]

I've seen this in some containers (prometheus, alertmanager, node-exporter, pushgateway, prom2json) , but I think it isn't everywhere yet:

$ docker run --entrypoint /bin/whoami prom/statsd-exporter
root

It would be great if you could start adapting it in the other containers as well.