Getting started with docker containers

Setup docker manually and run hello world docker style to ensure it is installed correctly.

What is docker?

Docker is an open-source project to easily create lightweight, portable, self-sufficient containers from any application. The same container that a developer builds and tests on a laptop can run at scale, in production, on VMs, bare metal, OpenStack clusters, public clouds and more.

Containers vs Virtual Machines

Virtual Machines: require a complete operating system image, with allocated resources to run. They take a long time to bootup, and have quite a bit of overhead.

Containers: are much more lightweight, since there is no overhead of a complete virtual environment, with the kernel managing the memory and access to the file system. This also means you can bootup an application in seconds.

Install docker

• Install virtualbox - (https://www.virtualbox.org)
• Launch a new VM, and install ubuntu 12.04 (64 bit) - (http://www.ubuntu.org)

Docker works best with the 3.8 kernel due to a bug in lxc which can cause some issues if you are on 3.2. run uname -r to check which version you are on, and run the following if you are not on 3.8

sudo apt-get update

sudo apt-get install linux-image-generic-lts-raring linux-headers-generic-lts-raring

sudo reboot

Run...

sudo apt-get update

sudo apt-get upgrade

sudo apt-get install python-software-properties git-core build-essentials ssh

sudo apt-get update

sudo add-apt-repository ppa:dotcloud/lxc-docker

sudo apt-get install lxc-docker

Now, hello world... docker style.

dock@saas:~$ sudo docker run ubuntu /bin/echo hello world
[sudo] password for dock: 
Pulling repository ubuntu
Pulling image 8dbd9e392a964056420e5d58ca5cc376ef18e2de93b5cc90e868a1bbc8318c1c (precise) from ubuntu
Pulling image b750fe79269d2ec9a3c593ef05b4332b1d1a02a62b4accb2c21d589ff2f5f2dc (quantal) from ubuntu
Pulling 27cf784147099545 metadata
Pulling 27cf784147099545 fs layer
Downloading 94.86 MB/94.86 MB (100%)
hello world

What just happened?

• docker downloaded the base image from the docker index
• it created a new LXC container
• It allocated a filesystem for it
• Mounted a read-write layer
• Allocated a network interface
• Setup an.lation
• And then executed a process in there
• Captured its output and printed it to you

In the next tip, we will discuss setting up a mongodb container manually, and then with a dockerfile.

Originally posted to: (http://blog.codiez.co.za/2013/09/hello-docker/)