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Docker - The Linux Container
1. Docker: The Linux container
Name: BalajiRajan
Date: 29-Sep-2013
Event:http://www.meetup.com/devops-bangalore
2. What is docker?
Docker is a tool created by the folks at dotCloud to make
using LinuX Containers (LXC) easier to use.
Linux Containers are basically light weight Virtual Machines
(VM). A linux container runs Unix processes with strong
guarantees of isolation across servers.
Your software runs repeatably everywhere because its
Container includes all of its dependencies.
3. LXC
Lxc is an operating system-level virtualization method for
running multiple isolated Linux systems (containers) on a
single control host.
Basicaly, LXC provides a way to run mini operating
systems in your host operating system.
4. What about VM?
● Any virtualization technologies such as KVM, Hypervisor
and Xen..etc, which started by booting separate virtual
systems on emulated hardware, and then new vm runs
as a full fledged OS and uses isolated process spaces.
● But Docker runs with Host Operating system as its
share the host process spaces.
6. Docker Vs VMs
Size:
VMs are very large which makes them
impractical to store and transfer.
VM: You have a container image that is 1GB in size. If
you wanted to use a Full VM, you would need to have
1GB times x number of VMs you want.
Docker: With LXC you can share the bulk of the 1GB. It
means that If you have 1000 containers you still might
only have a little over 1GB of space for the containers
OS, assuming they are all running the same OS image.
7. Docker Vs VMs
Resource Utilization: (CPU & RAM)
VM: A full virtualized system gets it's own set of
resources allocated to it, and does minimal sharing. You
get more isolation, but it is much heavier and requires
more resources.
Docker: With LXC you get less isolation, but they are
more lightweight and require less resources.
8. Docker Vs VMs
Performance:
VM: A full virtualized system usually takes minutes to
start.
Docker: LXC containers take seconds, and most times
less then a second.
9. Docker's Advantage
Throwable Sandboxes: Create a container in a minute
to test your stuffs and tear it down.
Fine Application Delivery: Containers allow you to
package just about any application. You could add the
dependencies of the application in the container itself.
Ex: mysql service.
Reusability: Docker makes containers reusbale.
Uniformity: Development and production Environments.
10. Installing Docker
* Docker is still under heavy development! Don’t
recommend using it in production yet.
* Right now, the officially supported distributions are:
* Ubuntu Precise 12.04 (LTS) (64-bit)
* Ubuntu Raring 13.04 (64 bit)
11. Installing Docker
Requirement:
* Kernel version: greater then 3.8 and Cgroups and
namespaces must be enabled.
* AUFS: AUFS is included in the kernels built by the
Debian and Ubuntu distributions.
* LXC:
Installation method
* Source
* compiled binary
* package manager
12. Installing Docker
# Add the Docker repository to your apt sources list.
sudo sh -c "echo deb http://get.docker.io/ubuntu docker main >
/etc/apt/sources.list.d/docker.list"
# Update your sources
sudo apt-get update
# Install, lxc-docker
sudo apt-get install lxc-docker
# download the base 'ubuntu' container and run bash inside it
#while setting up an interactive shell
sudo docker run -i -t ubuntu /bin/bash
13. Installing Docker
# docker version
Client version: 0.4.8
Server version: 0.4.8
# docker info
Containers: 0
Images: 0
WARNING: No memory limit support
WARNING: No swap limit support
14. Terminalogy
* Image
An image is a read only layer used to build a container. They
do not change.
* Container
Is basically a self contained runtime environment that is
built using one or more images. You can commit your
changes to a container and create an image.
* Docker index / registry
These are public or private servers where people can upload
their repositories so they can easily share what they made.
16. Lets see what docker is doing here.
1. Downloaded the image from docker repo.
2. Generated a new LXC container.
3. Created a new file system.
4. Mounted a read/write layer.
5. Allocated network interface.
6. Setup IP.
7. Setup NATing.
8 Executed the bash shell in the container.
*****All in under a very few minutes *********
17. Work with CLI:
* List Images:
$ docker images
REPOSITORY TAG ID CREATED SIZE
base latest b750fe79269d 3 months ago 24.65 kB
(virtual 180.1 MB)
base ubuntu-12.10 b750fe79269d 3 months ago 24.65 kB
(virtual 180.1 MB)
base ubuntu-quantal b750fe79269d 3 months ago 24.65 kB
(virtual 180.1 MB)
base ubuntu-quantl b750fe79269d 3 months ago 24.65 kB
(virtual 180.1 MB)
*List Containers:
$ docker ps -a
ID IMAGE COMMAND CREATED STATUS
PORTS
861361e27501 base:latest /bin/echo hello world 1 minutes ago Exit 0
18. Docker Index/registry
The Docker Registry is server that stores all of the
images and repositories. The Index just has the metadata
about the images, repositories and the user accounts, but
all of the images and repositories are stored in the
Docker Registry.
$ docker login
Username (): myusername
Password:
Email ():
myusername@example.com
Login Succeeded
19. Work with CLI:
Important commands:
* docker run base /bin/echo hello world
* docker commit <id>
* docker attach <id>
* docker pull / push <id>
* docker inspect <id>
* docker diff <id>
* docker stop/start <id>
* docker rmi `docker images -a -q` - remove images
* docker rm `docker ps -a -q` - remove container
20. More Projects are coming on the way...
● http://blog.docker.io/2013/07/docker-projects-from-the-docker-co
Important Projects:
* Building Docker on Openstack with Vagrant
* DockerUI – Web interface
* Openstack-Docker
* chef-docker - Installs/Configures Docker
* Puppet module for installing Docker
* dockermix – A command line tool to build and manage
multi-container docker environments
●
