add D-in-D dockerfile, update Readme

Dockerfile.dind

@@ -0,0 +1,33 @@
+# Use the official Docker docker-in-docker Alpine image as the base image
+FROM docker:dind
+
+# Set the working directory to /mrsk
+WORKDIR /mrsk
+
+# Copy the Gemfile, Gemfile.lock into the container
+COPY Gemfile Gemfile.lock mrsk.gemspec ./
+
+# Required in mrsk.gemspec
+COPY lib/mrsk/version.rb /mrsk/lib/mrsk/version.rb
+
+# Install system dependencies including ruby-dev
+RUN apk add --no-cache --update ruby-dev build-base git docker openrc \
+    && rc-update add docker boot \
+    && gem install bundler --version=2.4.3 \
+    && bundle install
+
+# Copy the rest of our application code into the container.
+# We do this after bundle install, to avoid having to run bundle
+# everytime we do small fixes in the source code.
+COPY . .
+
+# Install the gem locally from the project folder
+RUN gem build mrsk.gemspec && \
+    gem install ./mrsk-*.gem --no-document
+
+# Set the working directory to /workdir
+WORKDIR /workdir
+
+# Set the entrypoint to run the installed binary in /workdir
+# Example:  docker run -it -v "$PWD:/workdir" mrsk init
+ENTRYPOINT ["mrsk"]

README.md

@@ -6,7 +6,19 @@ Watch the screencast: https://www.youtube.com/watch?v=LL1cV2FXZ5I
 
 ## Installation
 
-Install MRSK globally with `gem install mrsk`. Then, inside your app directory, run `mrsk init` (or `mrsk init --bundle` within Rails apps where you want a bin/mrsk binstub). Now edit the new file `config/deploy.yml`. It could look as simple as this:
+Install MRSK globally with `gem install mrsk` or build a dockerized version:
+
+```sh
+docker build . -t mrsk:dind -t mrsk:latest -f Dockerfile.dind
+```
+
+If you build the docker version, add the following alias to your .${SHELL}rc file and re-source the rc file to allow ssh and docker to work within the container:
+
+```sh
+alias mrsk='docker run --rm -it -v $HOME/.ssh:/root/.ssh -v /var/run/docker.sock:/var/run/docker.sock -v ${PWD}/:/workdir mrsk'
+```
+
+Then, inside your app directory, run `mrsk init` (or `mrsk init --bundle` within Rails apps where you want a bin/mrsk binstub). Now edit the new file `config/deploy.yml`. It could look as simple as this:
 
 ```yaml
 service: hey
@@ -34,7 +46,7 @@ mrsk deploy
 This will:
 
 1. Connect to the servers over SSH (using root by default, authenticated by your ssh key)
-2. Install Docker on any server that might be missing it (using apt-get)
+2. Install Docker on any server that might be missing it (using apt-get): root access is needed via ssh for this.
 3. Log into the registry both locally and remotely
 4. Build the image using the standard Dockerfile in the root of the application.
 5. Push the image to the registry.