1. Containers and Virtualisation

2. What is Virtualisation?
At its simplest – isolation from underlying hardware
Hypervisors
VMware
Virtualbox
Qemu
Containers
Linux Containers (LXC)
Virtual Machine Applications
Java
Python

3. Why? Make better use of resources
Move workloads between physical systems
Run multiple OS on the same hardware
Create test environments

4. Hypervisors Host Operating System emulates machine hardware
Full OS sits on top of the hypervisor
Can have different OS in each Virtual Machine
Linux
Windows
OSX

5. Hypervisor VM 1 VM 2 VM 3 Applications Applications Applications
Guest OS
Guest OS
Guest OS
Virtual
Hardware
Virtual
Hardware
Virtual
Hardware
Hypervisor
Host OS
Hardware

6. Containers Guest containers share the same kernel and parts of the OS
More efficient use of resources
Only use what they require
BUT can only run the same OS (Linux)
Possible to have different distributions as longs as they are all running the same kernel

7. Host OS Kernel with Virtualisation Layer
Container
Container 1
Container 2
Container 3
Applications
Applications
Applications
Host OS Kernel with Virtualisation Layer
Hardware

8. Container Advantages Uses less resource than a full VM
More containers for the same hardware
Better use of resources
If Container1 & Container2 open the same file:
Host kernel open the file and reads page into Kernel page cache
If both read from the same position, they just get given the same page

9. Linux Containers LXC LXC contains processes in the kernel
Provides Kernel namespaces
ipc, uts, mount, pid, network and user
Apparmor & SELinux Profiles
Chroot (using pivot_root)
Control Groups (cgroups) for resource isolation
CPU, memory, block I/O, network, etc

10. LXC Components liblxc library Language bindings C, Python3, Ruby, etc
Userspace tools to control the containers

11. Using Containers Install apt-get install lxc Run
Create an Ubuntu type container called 'container1'
# Create
lxc-create -t ubuntu -n container1
# Start
lxc-start -n container1 -d
# Get info
lxc-ls --fancy container1
# Stop
lxc-stop -n container1
Start the container
Stop the container

12. Docker Package containers into a portable format
Linux Only (uses Linux Containers)
Share applications
Private
Between colleagues
Public
Docker Hub

13. Docker Components Docker Engine Applications Binaries Libraries App 1
Libs/Bins
Libs/Bins
Libs/Bins
Docker Engine
Host OS
Hardware

14. Docker Images A read-only template for an application
Contains a series of layers
Uses union file systems to combine layers into a single image
Can be saved to a Docker Registry

15. Docker Image Layers Starts with a base image
Extended with Instructions
Run a command
Add a file or directory
Create an environment variable
Define processes to run on launch
Can distribute just a change to a layer instead of an entire image

16. Docker Registries Registries contain Docker images Public or Private
Main public registry is the Docker Hub
Huge collection of pre-built images that can be pulled down as a starting point to create your own image

17. Docker Containers
The container holds everything needed for an application to run
Created from an Image
Can be
Run
Started
Stopped
Moved
Deleted
Isolated from each other and the rest of the system

18. Installing Docker Ubuntu 14.04 For other systems see
$ sudo apt-get update
$ sudo apt-get install docker.io
$ sudo sed -i '$acomplete -F _docker docker' /etc/bash_completion.d/docker.io
For other systems see

19. Hello World docker run <image name> <command>
$ sudo docker run ubuntu echo 'Hello World'
Unable to find image 'ubuntu' locally
Pulling repository ubuntu
[ Downloading Image ]
Hello World $
Docker has pulled a copy of the ubuntu image from the Docker Hub
The container stops when the command exits

20. Running Docker $ sudo docker run -i -t ubuntu /bin/bash
We are now running bash inside our Ubuntu container
-t creates a terminal inside the container
-i connects to STDIN of the container for interactive connections

21. Creating our Own Image
After we have made changes to an image, those changes need to be commited
$ sudo docker run -i -t ubuntu /bin/bash
apt-get install apache2 …
exit
$ sudo docker ps -l
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
93a2e27d4d49 ubuntu:latest /bin/bash 24 minutes ago Exited (0) naughty_shockley
$ sudo docker commit -m="Installed Apache" -a="Ming" 93A2e27d4d49 ming/apache
6d575ecf604809cf5b84b719afe74ba9588c72e4fdacbf2ca833f77f52e27309
-m Commit message
-a Name of creator
93A2e27d4d49 Container ID
ming/apache Name of new Image

22. Connecting to our Container
$ sudo docker run -i -t -p 8080:80 ming/apache /bin/bash
apache2ctrl start
-p <host port>:<container port>
Map a port from our host to a port in our container

23. Conclusion Containers are a lightweight means of virtualisation
BUT only on a Linux System
Docker simplifies the management and distribution of containers

24. Resources www.docker.com The Project Website www.docker.com/tryit
A sandbox to play with docker commands and images

25. Questions?