From zero to Docker

Giovanni Toraldo@ LuccaLUG

Docker: what is it?

Enables software developers to:

● package an application● with all dependencies● runs it everywhere unchanged

Docker: what is it?

Enables system administrators to

● simplify application deployment● ease scale-up & scale-down● processes separation

Underlying technologies

● Linux namespaces● Control Groups (cgroups)● Layered filesystems● LXC (now libcontainer)

Glossary

● Image: immutable snapshot of a container, push/pull repository

● Container: an instance launched from an image● Volume: persistent writable area of a container● Registry: repository of images (versioned via

tags)● Dockerfile: the descriptor from which an image

is built

How to install docker engine

● GNU/Linuxdeb https://apt.dockerproject.org/repo ubuntu-trusty maindeb https://apt.dockerproject.org/repo debian-jessie mainpacman -S docker

● Windows / OSXhttps://www.docker.com/products/docker-toolbox

Docker-machine

Machine manager (like Vagrant)

https://github.com/docker/machine

(Win/Mac: distributed in Docker toolkit)

● Launch VM somewhere● Install Docker● Generates and copy certificates

○ (password-less auth)

● Enable remote access via TCP

Docker-machine backends

Where nodes can run?

● Generic backend○ existing hosts with ssh access

● Local machine (virtualization)○ Virtualbox○ VMware Fusion

● Cloud providers○ Amazon○ GCE○ Rackspace○ DigitalOcean○ ...

Docker-machine bootstrap examples

$ docker-machine create --driver generic --generic-ip-address=<ip-address>

<nodename>

$ docker-machine create --driver virtualbox <nodename>

$ docker-machine create --driver digitalocean --digitalocean-access-token <token>

<nodename>

$ docker-machine create --driver amazonec2 --amazonec2-access-key <key> --

amazonec2-secret-key <secret> <nodename>

$ docker-machine create --driver kvm --kvm-cpu-count 2 --kvm-disk-size 20 --kvm-

memory 4096 <nodename>

Interaction with a Docker-machine node

$ docker-machine env defaultexport DOCKER_TLS_VERIFY="1"export DOCKER_HOST="tcp://192.168.99.100:2376"export DOCKER_CERT_PATH="/home/gionn/.docker/machine/machines/default"export DOCKER_MACHINE_NAME="default"# Run this command to configure your shell: # eval "$(docker-machine env default)"

$ docker infoKernel Version: 4.1.17-boot2dockerOperating System: Boot2Docker 1.10.0 (TCL 6.4.1); master : b09ed60 - Thu Feb 4 20:16:08 UTC 2016

Hello world

$ docker run -ti ubuntu:14.04 /bin/bash

● Live demo time

What happens under the hood?

● Pulls the ubuntu image from registry● Creates a new container

○ Allocates a rw filesystem○ Allocates a network interface (on a bridge)○ Sets up network (IP address, dns..)

● Launch a process in the container● Captures and provides application output

Container terminates when the process exit

Dockerfile (not the best example)

Standard workflow

Build & push:

● docker build -t gionn/nodejs-app:1.0.0 .○ a tagged image is generated

● docker push gionn/nodejs-app:1.0.0○ publish to repository

Pull & run:

● docker pull gionn/nodejs-app:1.0.0○ fetch from repository

● docker run gionn/nodejs-app:1.0.0○ run container from this image

Docker compose

Compose is a tool for defining and running multi-container Docker applications using a file in YML format.

$ docker-compose up

Examples:

https://github.com/ClouDesire/docker-compose-library

Thanks!