Docker

Overview

What is Docker

Docker is a way of deploying apps on servers. It packages apps into side-by-side containers. These are similar in spirit to virtual machines, but different because containers are not (or, don't have to be) fully bundled operating systems. The container system makes sure everything runs the same everywhere.

It's like Homebrew or Aptitude for apps.

Installing

Docker has great documentation on getting up and running: https://docs.docker.com/

Docker also provides several examples of docker-izing an app: https://docs.docker.com/engine/examples/

Ubuntu Linux

You can get docker running on many virtual hosting services.

Linode supports docker: https://blog.linode.com/2014/01/03/docker-on-linode/

They offer installation guides for different distributions: https://docs.docker.com/engine/installation/linux/#install-using-the-repository

Guide to installing Docker on Ubuntu Linux: https://docs.docker.com/engine/installation/linux/ubuntulinux/

Start by setting up Docker's repositories:

$ sudo apt-get install \
    apt-transport-https \
    ca-certificates \
    curl \
    software-properties-common

Add Docker's GPG key:

$ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

Verify fingerprint starts with 9DC8:

$ sudo apt-key fingerprint 0EBFCD88

Set up the stable repository:

$ sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"

Install docker by updating package index and running install:

$ sudo apt-get update
$ sudo apt-get install docker-ce

Test it out:

$ sudo docker run hello-world

Errors

When I added Docker's repos to my aptitude following the instructions above, I kept seeing 403 errors from docker's repo when I ran apt-get update:

sudo apt-get update
...
W: Failed to fetch https://download.docker.com/linux/ubuntu/dists/wily/stable/binary-amd64/Packages  HttpError403

Yuck. Others have had this issue too. [1]

Resolving

Resolved the problem by visiting their apt repos with a browser and manually downloading/installing the .deb file.

Start with the name of your release:

$ lsb_release -c
Codename:                     wily

Now navigate to their aptitude repositories in your browser: https://apt.dockerproject.org/repo/pool/main/d/docker-engine/

Find the deb file that corresponds to your install and copy the link.

$ wget <link to .deb file> 

Now you can install it (you probably need to be sudo):

$ dpkg -i docker-engine_1.9.1-0~wily_amd64.deb
Selecting previously unselected package docker-engine.
(Reading database ... 142272 files and directories currently installed.)
Preparing to unpack docker-engine_1.9.1-0~wily_amd64.deb ...
Unpacking docker-engine (1.9.1-0~wily) ...
Setting up docker-engine (1.9.1-0~wily) ...
Processing triggers for ureadahead (0.100.0-19) ...
Processing triggers for systemd (225-1ubuntu9.1) ...
Processing triggers for man-db (2.7.4-1) ...

Mac

You can run docker on Mac: https://docs.docker.com/docker-for-mac/

Docker on Linux Without Sudo

To modify Docker so it runs on Linux without requiring the use of the sudo command, create a docker group:

groupadd docker
usermod -a -G docker username

That's it - boom - you should be able to run the docker hello world without sudo:

$ docker hello-world # look ma, no sudo

Up and Running

post installation info: https://docs.docker.com/engine/installation/linux/linux-postinstall/#upstart

Test

Test you are up and running with a working install of docker:

$ docker --version
Docker version 17.03.0-ce, build 60ccb22

$ docker-compose --version
docker-compose version 1.11.2, build dfed245

$ docker-machine --version
docker-machine version 0.10.0, build 76ed2a6

$ docker version
Client:
 Version:      1.9.1
 API version:  1.21
 Go version:   go1.4.2
 Git commit:   a34a1d5
 Built:        Fri Nov 20 13:20:08 UTC 2015
 OS/Arch:      linux/amd64
Cannot connect to the Docker daemon. Is the docker daemon running on this host?

Hello world

$ sudo docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from hello-world

50a54e1f9180: Pull complete
7a5a2d73abce: Pull complete
Digest: sha256:7820f4620e6cf3e795643fac2f6b09e7fd0a29e7e5c4eee6aac9ba0bedca158c
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://cloud.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/engine/userguide/

web server

docker run -d -p 80:80 --name webserver nginx

Security Notes

Being in the docker group gives you serious root-level powers. Info about attack surface of Docker: https://docs.docker.com/engine/security/security/#docker-daemon-attack-surface