unit9/base repository overview

⁠Base image with runit-based service supervision

The image builds upon the latest Debian Jessie⁠, and adds a thin init + service supervision layer.

The purpose is mostly for internal use at UNIT9⁠, but there's nothing bundled that makes it UNIT9-specific.

PID 1 duties (spawn runit⁠, reap zombies) are handled with a simple Go program⁠ written by Peter Bourgon and hosted on Github, license MIT⁠.

Service supervision is handled with runit⁠.

Programs that insist on logging to syslog⁠ are handled with socklog⁠.

Source on Github: https://github.com/unit9/docklabs⁠

⁠Features and non-features

• Lean, for small and fast downloads! Includes only what's absolutely essential on top of debian:jessie;
• Makefile for easy builds and uploads:
  • make build to build
  • make push to push to Docker Hub
  • make shell gives you a shell in the (ephemeral) container
• Support for /etc/rc.local to initialise & self-check the container

⁠Using with your Dockerfile

Pull unit9/base:latest and customise this example:

FROM unit9/base:latest
MAINTAINER You <[email protected]>

RUN apt-get update && \
    apt-get install --yes my-favourite-stuff && \
    rm -rf /var/cache/apt /var/lib/apt/lists

ADD run_my_stuff /etc/service/run_my_stuff/run
ADD rc.local /etc/rc.local

VOLUME /data/run_my_stuff
EXPOSE 1234

Notice that neither cmd or exec are defined; this is the role that runit takes.

Inside the file run_my_stuff, there should be a shell script that reads the environment and sets up the service. For example:

#!/bin/sh
set -eu

echo $UPSTREAM_PORT | sed -E 's#tcp://(.+):(.+)#\1 \2#' | {
    read host port
    echo >&2 host=$host port=$port

    cat > /etc/my_stuff.conf <<EOF
name my_stuff
host $host
port $port
EOF
    }

echo >&2 "Starting my stuff"
exec /usr/bin/my-stuff --config /etc/my_stuff.conf

Inside of rc.local, is another simple shell script, which can perform any one-off initialisation tasks or self-checks:

#!/bin/sh
set -eux
test -f /var/www/html/index.html
lighttpd -t -f /etc/lighttpd/lighttpd.conf
exit 0

Make sure the script returns a non-zero code on an error. Your container will exit upon failure - this is useful to e.g. stop a bad deployment before the rolling update brings everything down.

⁠License

See the file LICENSE⁠.