Fix example docker run commands in README, to handle the Docker daemon entrypoint

Author: clareliguori

README.md

@@ -8,17 +8,22 @@ The master branch will sometimes have changes that are still in the process of b
 
 ### How to build Docker images
 
-Steps to build Ruby-2.3.1 image
+Steps to build Ruby 2.3.1 image
 
 * Run `git clone https://github.com/aws/aws-codebuild-docker-images.git` to download this repository to your local machine
-* Run `cd ubuntu/ruby/2.3.1` to change the directory in your local workspace. This is the location of Ruby-2.3.1 Dockerfile with Ubuntu base.
-* Run `docker build -t aws/codebuild/ruby-2.3.1 .` to build Docker image locally
-* Once succeeded, your can run `docker run -ti aws/codebuild/ruby-2.3.1 bash` to start container running `bash` shell with the ruby-2.3.1 image.
+* Run `cd ubuntu/ruby/2.3.1` to change the directory in your local workspace. This is the location of the Ruby 2.3.1 Dockerfile with Ubuntu 14.04 base.
+* Run `docker build -t aws/codebuild/ruby:2.3.1 .` to build Docker image locally
 
+To poke around in the image iteractively, build it and run:
+`docker run -it --entrypoint sh aws/codebuild/ruby:2.3.1 -c bash`
+
+To let the Docker daemon start up in the container, build it and run:
+`docker run -it --privileged aws/codebuild/ruby:2.3.1 bash`
 
 ```
 $ git clone https://github.com/aws/aws-codebuild-docker-images.git
 $ cd aws-codebuild-docker-images
 $ cd ubuntu/ruby/2.3.1
-$ docker build -t aws/codebuild/ruby-2.3.1 .
+$ docker build -t aws/codebuild/ruby:2.3.1 .
+$ docker run -it --entrypoint sh aws/codebuild/ruby:2.3.1 -c bash
 ```