Introducing Docker
Francesco Pantano
francesco.pantano@opmbx.it
March 17, 2016

#Outline
1 Virtualization
2 Containers
3 Docker in practice
4 Docker Compose
5 Continuous integration
Virtualization 2/24

Thinking about VMM
The Key component is the Hypervisor, a Virtual Machine Monitor
that can be thought as an API that provides access to the hw level
for the VMs.
Hosted ()
abstract guest operating
systems from the host one
Bare Metal()
run directly on the host’s
hardware
VMware Workstation/Player, VirtualBox and QEMU are examples
of hosted hypervisors
Virtualization 3/24

Deep into Light Virtualization
Born on top of LXC project, a set of tools built on a userspace
interface for the Linux kernel containment features, LV uses the
following kernel features to contain processes:
Kernel namespaces (ipc, uts, mount, pid, network and user)
Chroots (using pivot root)
CGroups (control groups)
Relies on your existing
system;
Services stay in the kernel
host;
Virtualization 4/24

Cgroups
Cgroups (abbreviated from control groups) is a Linux kernel feature
that limits, accounts for and isolates the resource usage (CPU,
memory, disk I/O, network, etc.) of a collection of processes.
Cgroups provides:
Resource Limiting: groups can be set to not exceed a
configured memory limit
Prioritization: some groups may get a larger share of CPU
utilization or disk I/O
Accounting: measures how much resources certain systems
use
Control: freezing the groups of processes, their checkpointing
and restarting
Virtualization 5/24

Namespaces
Isolation
Groups of processes are separated so they cannot ”see” resources
in other groups. For example, a PID namespace provides a
separate enumeration of process identifiers within each namespace.
struct upid {
int nr; // the PID value
// namespace where this PID is
relevant
struct pid_namespace *ns;
// ...
};
struct pid {
// number of upids
int level;
// array of upids
struct upid numbers [0];
};
Virtualization 6/24

The Layered Filesystem
Union file systems, or UnionFS, are file systems that operate by
creating layers, making them very lightweight and fast.
Copy-On-Write
It enables sharing that promotes smaller images
Virtualization 7/24

#Outline
1 Virtualization
2 Containers
3 Docker in practice
4 Docker Compose
5 Continuous integration
Containers 8/24

Why Containers?
Fast deployment time
It’s cheap and flexible
Scalability and support
Docker as standardized platform
Docker is a platform for developing, shipping,
and running applications using container
virtualization technology.
Containers 9/24

The Docker environment
Containers 10/24

Docker: Terminology
Image: layered filesystem where each layer references the layer
below
Dockerfile: build script that defines:
an existing image as starting point
a set of instructions that augment that
image (each of which results in another
layered filesystem)
metadata such as ports exposed
the command to executed when the
image is run
Container: runtime instance of an image
plus a read/write layer
Docker Hub: centralized repository of docker images
Containers 11/24

#Outline
1 Virtualization
2 Containers
3 Docker in practice
4 Docker Compose
5 Continuous integration
Docker in practice 12/24

Quick Start
Linux - run natively e.g. on Ubuntu
apt-get install docker.io
curl -sSL https://get.docker.com/ubuntu — sh
Mac / Windows run under VirtualBox
http://boot2docker.io
Docker Machine - https://github.com/docker/machine
docker machine -d virtual-box dev
docker machine -d openstack test
docker machine -d softlayer ... prod
Verify ..
$ docker version
Client/Server:
Version: 1.9.1
OS/Arch: linux/amd64
.. your installation
$ docker info
Client/Server:
Version: 1.9.1
OS/Arch: linux/amd64
Docker in practice 13/24

Quick Start
Linux - run natively e.g. on Ubuntu
apt-get install docker.io
curl -sSL https://get.docker.com/ubuntu — sh
Mac / Windows run under VirtualBox
http://boot2docker.io
Docker Machine - https://github.com/docker/machine
docker machine -d virtual-box dev
docker machine -d openstack test
docker machine -d softlayer ... prod
Verify ..
$ docker version
Client/Server:
Version: 1.9.1
OS/Arch: linux/amd64
.. your installation
$ docker info
Client/Server:
Version: 1.9.1
OS/Arch: linux/amd64
Docker in practice 13/24

Quick Start
Linux - run natively e.g. on Ubuntu
apt-get install docker.io
curl -sSL https://get.docker.com/ubuntu — sh
Mac / Windows run under VirtualBox
http://boot2docker.io
Docker Machine - https://github.com/docker/machine
docker machine -d virtual-box dev
docker machine -d openstack test
docker machine -d softlayer ... prod
Verify ..
$ docker version
Client/Server:
Version: 1.9.1
OS/Arch: linux/amd64
.. your installation
$ docker info
Client/Server:
Version: 1.9.1
OS/Arch: linux/amd64
Docker in practice 13/24

Quick Start
Linux - run natively e.g. on Ubuntu
apt-get install docker.io
curl -sSL https://get.docker.com/ubuntu — sh
Mac / Windows run under VirtualBox
http://boot2docker.io
Docker Machine - https://github.com/docker/machine
docker machine -d virtual-box dev
docker machine -d openstack test
docker machine -d softlayer ... prod
Verify ..
$ docker version
Client/Server:
Version: 1.9.1
OS/Arch: linux/amd64
.. your installation
$ docker info
Client/Server:
Version: 1.9.1
OS/Arch: linux/amd64
Docker in practice 13/24

The Docker command line
docker search
Search for images in the docker hub
docker pull
Get a selected image from the docker hub
docker images
List all downloaded images
docker run
start a container
docker ps
List running images
docker build
Build an image from a Dockerfile
docker start/stop/kill
Containers management
docker rm/rmi
Remove a container / image
Docker in practice 14/24

Run your first container
$ docker search ubuntu
NAME DESCRIPTION STARS OFFICIAL A
ubuntu Ubuntu is a Debian-based Linux operating s... 3132 [OK] [
ubuntu-upstart Upstart is an event-based replacement for... 61 [OK] [
$ docker pull ubuntu:latest
latest: Pulling from library/ubuntu
92ec6d044cb3: Downloading 34.57 MB/65.68 MB
Digest: sha256:457b0587384bdhuis83290....6db5ae3934307c757c54
Status: Downloaded newer image for ubuntu:latest
$ docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
ubuntu latest 6cc0fc2a5ee3 1 minutes ago 187.9 MB
chef-server latest f3cd15749fa8 21 months ago 1.043 GB
$ docker run -i -t ubuntu /bin/bash
root@e550480534b1:/# apt-get update && apt-get install -y nginx
Docker in practice 15/24

Run your first container
$ docker search ubuntu
NAME DESCRIPTION STARS OFFICIAL A
ubuntu Ubuntu is a Debian-based Linux operating s... 3132 [OK] [
ubuntu-upstart Upstart is an event-based replacement for... 61 [OK] [
$ docker pull ubuntu:latest
latest: Pulling from library/ubuntu
92ec6d044cb3: Downloading 34.57 MB/65.68 MB
Digest: sha256:457b0587384bdhuis83290....6db5ae3934307c757c54
Status: Downloaded newer image for ubuntu:latest
$ docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
ubuntu latest 6cc0fc2a5ee3 1 minutes ago 187.9 MB
chef-server latest f3cd15749fa8 21 months ago 1.043 GB
$ docker run -i -t ubuntu /bin/bash
root@e550480534b1:/# apt-get update && apt-get install -y nginx
Docker in practice 15/24

Run your first container
$ docker search ubuntu
NAME DESCRIPTION STARS OFFICIAL A
ubuntu Ubuntu is a Debian-based Linux operating s... 3132 [OK] [
ubuntu-upstart Upstart is an event-based replacement for... 61 [OK] [
$ docker pull ubuntu:latest
latest: Pulling from library/ubuntu
92ec6d044cb3: Downloading 34.57 MB/65.68 MB
Digest: sha256:457b0587384bdhuis83290....6db5ae3934307c757c54
Status: Downloaded newer image for ubuntu:latest
$ docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
ubuntu latest 6cc0fc2a5ee3 1 minutes ago 187.9 MB
chef-server latest f3cd15749fa8 21 months ago 1.043 GB
$ docker run -i -t ubuntu /bin/bash
root@e550480534b1:/# apt-get update && apt-get install -y nginx
Docker in practice 15/24

Run your first container
$ docker search ubuntu
NAME DESCRIPTION STARS OFFICIAL A
ubuntu Ubuntu is a Debian-based Linux operating s... 3132 [OK] [
ubuntu-upstart Upstart is an event-based replacement for... 61 [OK] [
$ docker pull ubuntu:latest
latest: Pulling from library/ubuntu
92ec6d044cb3: Downloading 34.57 MB/65.68 MB
Digest: sha256:457b0587384bdhuis83290....6db5ae3934307c757c54
Status: Downloaded newer image for ubuntu:latest
$ docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
ubuntu latest 6cc0fc2a5ee3 1 minutes ago 187.9 MB
chef-server latest f3cd15749fa8 21 months ago 1.043 GB
$ docker run -i -t ubuntu /bin/bash
root@e550480534b1:/# apt-get update && apt-get install -y nginx
Docker in practice 15/24

The Dockerfile
Dockerfile instruct on how to build the image automatically
Dockerfile syntax:
FROM
RUN
ENV
EXPOSE
ADD
CMD
$ docker build -t fmount/nginx .
$ docker run -d -p 80 –name mystaticwebsite -v
$PWD/website:/var/www/html/website fmount/nginx nginx
Docker in practice 16/24

The Docker Hub
It provides a mechanism to share images in the docker-hub, a
repository of shareable collection of tagged images
$ docker commit/login
Exercise: Be Social :D
Register in the Docker Hub
Connect it to your Github and build
Docker in practice 17/24

#Outline
1 Virtualization
2 Containers
3 Docker in practice
4 Docker Compose
5 Continuous integration
Docker Compose 18/24

Get an app running in one command
#!/ bin/python
from flask import Flask
from redis import Redis
app = Flask(__name__)
redis = Redis(host="localhost" ,
port =6379)
@app.route("/")
def hello ():
redis.incr("hits")
return "I have been seen %s
times .n"
% redis.get("hits")
if __name__ == "__main__":
app.run(host="0.0.0.0", debug=
True)
requirements.txt
flask package
redis package
Docker Compose 19/24

Get an app running in one command
Steps to follow
Write your Dockerfiles
Build your containers
Prepare your application
Think about the infrastructure
Compose in a Microservices fashion
Build and start the containers
$ docker-compose up
Docker Compose 20/24

#Outline
1 Virtualization
2 Containers
3 Docker in practice
4 Docker Compose
5 Continuous integration
Continuous integration 21/24

Use case: Continuous Integration
Continuous integration 22/24

Thank you! Questions?
More examples at
https://github.com/fmount/containers
Continuous integration 23/24

References
The Docker Book
www.dockerbook.com
How2dock
https://github.com/how2dock/docbook
Docker in Action
https://www.manning.com/books/docker-in-action
Official doc
https://docs.docker.com/
SlideShare Docker Channel
http://www.slideshare.net/Docker/
Golang tour :D
https://tour.golang.org/
Continuous integration 24/24