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Docker

Documentation notes for using Docker https://docker.com/.

Brief

Docker is application that builds containers to host your own isolated Operating Systems. You can create your Docker Image with any service/language and deploy them to your servers. This saves time provisioning for every server.

I think the main benefit is that you could accidently mess up your docker container, and your real server won't be affected. You could just repull the image.

Create Docker Container

$ sudo docker pull debian

or Create and Run

$ sudo docker run debian
$ sudo docker run ubuntu:14.04

Run Docker Interactively

This is just like accessing a virtual machine, but's it's a docker container.

  • The -t means seudo-tty inside the new container

  • The -i means allows interactive mode via STDIN

  • The ubuntu is the docker container name, you can see them with $ docker images

    • You want to connect with from the image list repository:tag
    • If you had ubuntu:12.04 and ubuntu:14.04 in the image list, you can connect just using ubuntu and it will appear as ubuntu:latest

  • The /bin/bash is the shell to use.

    $ sudo docker run -t -i debian /bin/bash $ sudo docker run -t -i ubuntu:14.04 /bin/bash

See what's running in Containers

When you run this notice the "Names" column auto generated for running processes.

$ sudo docker ps

Mine created one called romantic_franklin, I can see anyone processes via:

$ sudo docker logs romantic_franklin

Stopping/Starting a container

$ sudo docker stop romantic_franklin
$ sudo docker start romantic_franklin

Check the Status of the container

$ sudo docker ps

Testing a Flask Container

This will download the dependencies, and the command python app.py runs it. Make sure you find the name of the container with $ sudo docker ps it will be different from below.

  • The -d runs in detached mode (in the background)

  • The -P lets Docker mapp to ports exposed from the image to our host.

    $ sudo docker run -d -P training/webapp python app.py $ sudo docker ps

Visit http://localhost:5000

We can change the port with

$ sudo docker run -d -p 5000:5000 training/webapp python app.py

To see a port provide the name (Remember $ sudo docker ps), this is an easier way:

$ sudo docker port insane_mclean 5000

See the logs of the flask container

$ sudo docker logs insane_mclean

See the processes running in a container

$ sudo docker top insane_mclean

Inspecting a Container

See the entire configuration in JSON format

$ sudo docker inspect insane_mclean

We can grab the IP address with

$ sudo docker inspect -f '{{ .NetworkSettings.IPAddress }}' insane_mclean

Delete a Container

When deleting a container it is permanent.

$ sudo docker stop insane_mclean
$ sudo docker rm insane_mclean

Search for Existing containers

This will list items from the docker public repositories

$ sudo docker search lamp

Update/Commit Image

We can setup this docker

$ sudo docker pull training/sinatra

Then connect

$ sudo docker run -t -i training/sinatra /bin/bash

Since we are going to exit after making a change (It's interactive mode, not running in the background), make sure to copy the root@a1f22b0f0476:/# @<hash>

Inside docker make a change, such as install JSON

$ gem install json

So we made a simple change now commit

$ sudo docker commit -m="Added gem" -a="Jesse Boyer" a1f22b0f0476

We can also tag the image

$ sudo docker commit -m="Added gem" -a="Jesse Boyer" a1f22b0f0476 jesse/sinatra:2

See the changes (You'll see two sinatra REPOSITORIES)

$ sudo docker images

Use the newly commited container

$ sudo docker run -t -i jesse/sinatra:2 /bin/bash

Creating a container from scratch

$ mkdir docker
$ cd docker
$ touch Dockerfile

Include the following in Dockerfile

# This is a comment
FROM ubuntu:14.04
MAINTAINER Jesse Boyer <myself@mysite.com>
RUN apt-get update && apt-get install -y ruby ruby-dev
RUN gem install sinatra

Build the file (Make sure to check $ sudo docker images)

$ sudo docker build -t="jesse/sinatra:2" .

With an image created, we can now create containers based off that

$ sudo docker run -t -i jesse/sinatra:2 /bin/bash

You will notice that the virtual machine name is different then when you first installed it. Mine being 3c2cb985d352 now, at first it was a1f22b0f0476.

Tag your image

$ sudo docker tag 3c2cb985d352 jesse/sinatra:dev

Using Docker Hub (The SaaS)

See https://registry.hub.docker.com/plans/

Push to the docker host

$ sudo docker push jesse/sinatra

Removing from the Hub

$ sudo docker rmi jesse/sinatra

Linking Containers

I didn't get this far yet.