Install Docker using a Dockerfile - scala

Question

I have a Dockerfile that looks like this:
# Pull base image
FROM openjdk:8
ENV SCALA_VERSION 2.12.2
ENV SBT_VERSION 0.13.15
# Scala expects this file
RUN touch /usr/lib/jvm/java-8-openjdk-amd64/release
# Install Scala
## Piping curl directly in tar
RUN \
curl -fsL http://downloads.typesafe.com/scala/$SCALA_VERSION/scala-$SCALA_VERSION.tgz | tar xfz - -C /root/ && \
echo >> /root/.bashrc && \
echo 'export PATH=~/scala-$SCALA_VERSION/bin:$PATH' >> /root/.bashrc
# Install sbt
RUN \
curl -L -o sbt-$SBT_VERSION.deb http://dl.bintray.com/sbt/debian/sbt-$SBT_VERSION.deb && \
dpkg -i sbt-$SBT_VERSION.deb && \
rm sbt-$SBT_VERSION.deb && \
apt-get update && \
apt-get install sbt && \
sbt sbtVersion
# Install Docker
RUN \
# if we have older versions, let's get rid of them first
apt-get install docker
# Define working directory
WORKDIR /root
What I want to do is, I would like to install Docker into this image and be able to run docker commands form within. How do I start the installed docker instance?

Answer 1

You can install the docker client binary only and share dockerd with the container and host.
Here is an example Dockerfile:
FROM openjdk:8
# Install your dependencies
# ...
# Install curl
RUN apt-get update && apt-get install -y \
curl \
&& rm -rf /var/lib/apt/lists/*
# Install docker client
ENV DOCKER_CHANNEL stable
ENV DOCKER_VERSION 17.03.1-ce
ENV DOCKER_API_VERSION 1.27
RUN curl -fsSL "https://download.docker.com/linux/static/${DOCKER_CHANNEL}/x86_64/docker-${DOCKER_VERSION}.tgz" \
| tar -xzC /usr/local/bin --strip=1 docker/docker
Build the image:
$ docker build -t docker-client .
Run a docker container with mounting /var/run/docker.sock, and then you can use docker command in the container:
$ docker run --rm -it -v /var/run/docker.sock:/var/run/docker.sock docker-client /bin/bash
root#c696b78206a8:/# docker version
Client:
Version: 17.03.1-ce
API version: 1.27
Go version: go1.7.5
Git commit: c6d412e
Built: Mon Mar 27 16:58:30 2017
OS/Arch: linux/amd64
Server:
Version: 17.05.0-ce
API version: 1.29 (minimum version 1.12)
Go version: go1.7.5
Git commit: 89658be
Built: Thu May 4 21:43:09 2017
OS/Arch: linux/amd64
Experimental: false
Note that mounting the docker.sock means that the container is permitted access to the docker host. Please be aware that there are potential security risks.

Answer 2

I would recommend you that use the official "dind" image (docker in docker): https://hub.docker.com/_/docker/ . However you will need to rewrite your Dockerfile.
FROM docker:dind-stable
# Install your stuff
And, take into account this:
Although running Docker inside Docker is generally not recommended, there are some legitimate use cases, such as development of Docker itself.