Smaller docker image based on Alpine Linux (166MB)

Setup, Configuration and Use Runtime
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I wanted to see if I could create a smaller docker image then the current options available at github.com/openhab/openhab-docker.

I was able to create a much smaller working image based on Alpine Linux; 166MB vs 720MB:

$ docker images
REPOSITORY                                    TAG                             IMAGE ID            CREATED             SIZE
testing/openhab-alpine-3.5-aarch64            latest                          972ffb817643        9 seconds ago       166MB
openhab/openhab                               2.1.0-snapshot-arm64            4fd4f2a72745        3 weeks ago         720MB

Dockerfile

FROM multiarch/alpine:aarch64-v3.5

# Download URLs
ENV OPENHAB_URL="https://openhab.ci.cloudbees.com/job/openHAB-Distribution/lastSuccessfulBuild/artifact/distributions/openhab/target/openhab-2.1.0-SNAPSHOT.tar.gz"

# Set variables
ENV APPDIR="/openhab"

# Install packages
RUN apk update && \
    apk add wget && \
    apk add openjdk8
# Note: Azul JDK did not work for me, so using openjdk8

# Install openhab
RUN mkdir ${APPDIR} && \
    wget -O openhab.tar.gz ${OPENHAB_URL} && \
    tar -xzf openhab.tar.gz --directory ${APPDIR} && \
    rm openhab.tar.gz

# Modify run script to use #!/bin/sh instead of #!/bin/bash
RUN sed -i "1s/bash/sh/" ${APPDIR}/runtime/bin/karaf

# Expose volume with configuration and userdata dir
VOLUME ${APPDIR}/conf ${APPDIR}/userdata ${APPDIR}/addons

# Execute command
WORKDIR ${APPDIR}
EXPOSE 8080 8443 5555
CMD ["./start.sh"]

Build

$ docker build . -t testing/openhab-alpine-3.5-aarch64

Run

docker run \
        --name openhab \
        -v /opt/openhab/conf:/openhab/conf \
        -v /opt/openhab/userdata:/openhab/userdata \
        -v /opt/openhab/addons:/openhab/addons \
        -p 8080:8080 \
        -p 8443:8443 \
        -p 5555:5555 \
        -d \
        --restart=always \
        testing/openhab-alpine-3.5-aarch64

I tested on Pine64-like hardware with a 4.10 linux kernel. This image will work on arm64 or aarch64 devices but it should also run on other devices like am64 by changing the FROM line, for example:

FROM multiarch/alpine:x86_64-v3.5