introducing docker

Introducing Docker

Francesco [email protected]

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 Monitorthat can be thought as an API that provides access to the hw levelfor the VMs.

I Hosted ()I abstract guest operating

systems from the host one

I Bare Metal()I run directly on the host’s

hardware

VMware Workstation/Player, VirtualBox and QEMU are examplesof hosted hypervisors

Virtualization 3/24

Deep into Light Virtualization

Born on top of LXC project, a set of tools built on a userspaceinterface for the Linux kernel containment features, LV uses thefollowing kernel features to contain processes:

I Kernel namespaces (ipc, uts, mount, pid, network and user)

I Chroots (using pivot root)

I CGroups (control groups)

I Relies on your existingsystem;

I Services stay in the kernelhost;

Virtualization 4/24

Cgroups

Cgroups (abbreviated from control groups) is a Linux kernel featurethat limits, accounts for and isolates the resource usage (CPU,memory, disk I/O, network, etc.) of a collection of processes.

Cgroups provides:

I Resource Limiting: groups can be set to not exceed aconfigured memory limit

I Prioritization: some groups may get a larger share of CPUutilization or disk I/O

I Accounting: measures how much resources certain systemsuse

I Control: freezing the groups of processes, their checkpointingand restarting

Virtualization 5/24

Namespaces

Isolation

Groups of processes are separated so they cannot ”see” resourcesin other groups. For example, a PID namespace provides aseparate 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 bycreating 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


4 Docker Compose


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 containervirtualization technology.

Containers 9/24

The Docker environment

Containers 10/24

Docker: Terminology

Image: layered filesystem where each layer references the layerbelow

Dockerfile: build script that defines:I an existing image as starting pointI a set of instructions that augment that

image (each of which results in anotherlayered filesystem)

I metadata such as ports exposedI the command to executed when the

image is run

Container: runtime instance of an imageplus a read/write layer

Docker Hub: centralized repository of docker images

Containers 11/24

#Outline

1 Virtualization

2 Containers


4 Docker Compose


Docker in practice 12/24

Quick Start

I Linux - run natively e.g. on UbuntuI apt-get install docker.io

I curl -sSL https://get.docker.com/ubuntu — sh

I Mac / Windows run under VirtualBoxI http://boot2docker.io

I Docker Machine - https://github.com/docker/machineI docker machine -d virtual-box devI docker machine -d openstack test

I docker machine -d softlayer ... prod

Verify ..

$ docker versionClient/Server:Version: 1.9.1OS/Arch: linux/amd64

.. your installation

$ docker infoClient/Server:Version: 1.9.1OS/Arch: linux/amd64


The Docker command line

I docker searchSearch for images in the docker hub

I docker pullGet a selected image from the docker hub

I docker imagesList all downloaded images

I docker runstart a container

I docker psList running images

I docker buildBuild an image from a Dockerfile

I docker start/stop/killContainers management

I docker rm/rmiRemove a container / image


Run your first container

I $ docker search ubuntu

NAME DESCRIPTION STARS OFFICIAL AUTOMATEDubuntu Ubuntu is a Debian-based Linux operating s... 3132 [OK] [OK]ubuntu-upstart Upstart is an event-based replacement for... 61 [OK] [OK]

I $ docker pull ubuntu:latest

latest: Pulling from library/ubuntu92ec6d044cb3: Downloading 34.57 MB/65.68 MBDigest: sha256:457b0587384bdhuis83290....6db5ae3934307c757c54Status: Downloaded newer image for ubuntu:latest

I $ docker images

REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZEubuntu latest 6cc0fc2a5ee3 1 minutes ago 187.9 MBchef-server latest f3cd15749fa8 21 months ago 1.043 GB

I $ docker run -i -t ubuntu /bin/bash

root@e550480534b1:/# apt-get update && apt-get install -y nginx


The Dockerfile

I Dockerfile instruct on how to build the image automatically

I Dockerfile syntax:

I FROM

I RUN

I ENV

I EXPOSE

I ADD

I CMD

$ docker build -t fmount/nginx .

$ docker run -d -p 80 –name mystaticwebsite -v$PWD/website:/var/www/html/website fmount/nginx nginx


The Docker Hub

It provides a mechanism to share images in the docker-hub, arepository of shareable collection of tagged images

$ docker commit/login

Exercise: Be Social :DI Register in the Docker Hub

I Connect it to your Github and build


#Outline

1 Virtualization

2 Containers


4 Docker Compose


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

I flask package

I redis package


Get an app running in one command

Steps to follow

I Write your Dockerfiles

I Build your containers

I Prepare your application

I Think about the infrastructure

I Compose in a Microservices fashion

Build and start the containers

$ docker-compose up


#Outline

1 Virtualization

2 Containers


4 Docker Compose


Continuous integration 21/24

Use case: Continuous Integration


Thank you! Questions?

More examples athttps://github.com/fmount/containers


References

The Docker Bookwww.dockerbook.com

How2dockhttps://github.com/how2dock/docbook

Docker in Actionhttps://www.manning.com/books/docker-in-action

Official dochttps://docs.docker.com/

SlideShare Docker Channelhttp://www.slideshare.net/Docker/

Golang tour :Dhttps://tour.golang.org/


introducing docker

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