Docker Basics
===

I looked at the "getting started" tutorial at <https://docs.docker.com/engine/getstarted/> and the "dockerfile reference" at <https://docs.docker.com/engine/reference/builder/>. Both of these websites were helpful.

installation
---

Here's what I needed to install in order to create and test Docker images on Mac:

  1. virtualBox
    - Provides the virtual machine in which to run docker images.
    - I had previously installed this, so I use the existing installation.
	- It is possible to use other programs such as VMware, OpenStack, etc.
    - You don't have to do much with this directly once it is installed. It works with `docker-machine` in the background.
  1. docker
    - Tools for creating and managing docker images.
	- I installed this with `brew install docker`.
  1. docker-machine
    - Tools for managing docker-machines.
	- I installed this with `brew install docker-machine`.

create and start machine
---

  - `docker-machine create -d virtualbox testingDocker` **creates** a machine with virtualbox called `testingDocker`.
  - You can check your docker-machines with `docker-machine ls`.
  - `docker-machine start testingDocker` will **start** the machine.
  - `docker-machine ip testingDocker` displays the IP of the machine.
  - `docker-machine env testingDocker` displays some information about the running machine.
    - `eval $(docker-machine env testingDocker)` to **setup your shell** for the running machine. Otherwise the `docker` tool won't work and you might get the error message:
	
`Cannot connect to the Docker daemon. Is the docker daemon running on this host?`

  - `docker-machine stop testingDocker` **stops** the machine

hello world image
---

  - check your docker images with `docker images`
  - run hello-world with `docker run hello-world`
    - If the image is not available locally, it will look for it at docker hub and download if it is found there.
  - run a bash shell with `docker run -it ubuntu bin/bash`

port assignment with BMEG web portal
---

  - Search docker hub at <https://hub.docker.com/>.
  - download a docker image with `docker pull bmeg/web-portal`
  - start the web app image with `docker run -p 3100:3000 -e ROOT_URL="http://localhost" bmeg/web-portal`
    - `-p` maps image port to a host port
	- `-e` sets environment variables to use in the running image
  - `docker ps` shows information about currently running docker images

building a docker image
---

Docker images are built by creating a `Dockerfile`. The Dockerfile reference (<https://docs.docker.com/engine/reference/builder/>) describes the commands. Images can be built up from a base image using `FROM node:0.10.46`. The basic strategy I used was:

  1. set up running environment with `RUN`, `EXPOSE`, and `ENV`
  1. copy built web app into the image with `COPY`
  1. install the app with `RUN`
  1. setup default commands with `CMD`
  1. **build** your image with `docker build --tag bmeg/web-portal .`
  1. check that the image was build with `docker images`
  1. test the image by running it

sharing your docker image
---

  1. Login to <https://hub.docker.com/>.
  1. Create a repository.
    - **Be sure to include information about how to run your docker image!**
  1. **push the image** to docker hub with `docker push bmeg/web-portal`

managing multi-container apps
---

Docker networking allows you to configure the container and host ports for services. However, it may be better to use the `docker-compose` tool for this configuration. I only know that such a tool exists and that it is configured via a `docker-compose.yml` configuration file. More information about `docker-compose` at <https://docs.docker.com/compose/>.