Introduction to docker

Introduction to Introduction to dockerdocker

What will be in this talk

- Overview of docker features- Overview of docker building blocks- Comparison to other solutions- Quick docker tutorial- Dockerfile tips

What will not be in this talk

- Exploiting docker- Details of deploying docker infrastructure- Deep technical descriptions

Easy to learn

- Easy to learn- Easy to learn- Cool whale- Cool whale- Written in go- Written in go

But seriously?But seriously?

Architecture changes

http://martinfowler.com/articles/microservices/images/decentralised-data.png

Features - images

● Package every app in the same box (dependencies, working everywhere)

● Isolate things from each other● Standarized build procedure (Dockerfile)

ContainersContainers

Features - containers

● Managing containers– Running & stopping

– Inspect, logs, top, ps

– Save & load (from files)

– Diff & commit

● Mounting volumens– Share data

– Persistency

● Easy networking and linking containers

Works on Works on everyone'severyone's machinemachine

IsolationIsolation

PortabilityPortability

Features - workflow

● Docker deamon and cli● Docker hub and registry● Image versioning (pull, commit, pull, layers)

Docker building Docker building blocksblocks

How it's How it's cooked?cooked?

NamespacesNamespaces

http://blog.dotcloud.com/under-the-hood-linux-kernels-on-http://blog.dotcloud.com/under-the-hood-linux-kernels-on-dotcloud-partdotcloud-part

One of the overall goals of namespaces is to support the implementation of containers, a tool for lightweight virtualization.

Namespaces - GOAL

Wrap a particular global system resource in an abstraction that makes it appear to the processes within the namespace that they have their own isolated instance of the global resource

Namespaces - HOW

Processes 'think' that they are the only processes on the system

Namespaces - Result

- pid

- numbering

- hierarchy

- cannot kill / ptrace in other namespaces

- net

- 20 apaches at 80

- mount

Namespaces - Examples

Control Control groupsgroups

http://blog.dotcloud.com/kernel-secrets-from-the-paas-garage-http://blog.dotcloud.com/kernel-secrets-from-the-paas-garage-part-24-cpart-24-c

Measure and limit resource usage for groups of

processes

Control groups

Docker vs VMDocker vs VM

Overhead

http://www.zdnet.com/what-is-docker-and-why-is-it-so-darn-popular-7000032269/

LightweightLightweightAndAndfastfast

Sharing OSSharing OS

Higher densityHigher density

Not really a VMNot really a VM

Why docker? Why docker? Why not lxc?Why not lxc?

Why docker? Why docker? Why not lxc?Why not lxc?

Why docker? Why docker? Why not lxc?Why not lxc?

Why docker? Why docker? Why not lxc?Why not lxc?

http://stackoverflow.com/questions/17989306/what-does-docker-add-to-just-plain-lxc

Docker tutorialDocker tutorial

Pull it!Pull it!$ docker pull busybox

● Search docker registry for repository of given name

● Downloads the repository

● Pulls only changes next time

Pull it!Pull it!$ docker pull busybox

● Search docker registry for repository of given name

● Downloads the repository

● Pulls only changes next time

Pull it!Pull it!$ docker pull busybox

● Search docker registry for repository of given name

● Downloads the repository

● Pulls only changes next time

Run it!Run it!$ docker run busybox:ubuntu-14.04 echo "hello"

● Make sure that image is available (downloads if not found)

● Create a container● Run a command

Run it!Run it!$ docker run -it busybox:ubuntu-14.04 sh

● -it → makes container interactive

● Create a container● Give you a shell

access

More complicated example

● Run redis in a container

● Run it as a deamon

● Bind it to network● Make storage

persistent

Run it!Run it!$ docker run -d -v /var/docker/redis:/data -p 6379:6379 --name=redis dockerfile/redis

● -d → launch as deamon

● -v /var/docker/redis:/data → mount directories

● -p 6379:6379 → forward ports

Run it!Run it!$ docker run -d -v /var/docker/redis:/data -p 6379:6379 --name=redis dockerfile/redis

● -d → launch as deamon

● -v /var/docker/redis:/data → mount directories

● -p 6379:6379 → forward ports

Run it!Run it!$ docker run -d -v /var/docker/redis:/data -p 6379:6379 --name=redis dockerfile/redis

● -d → launch as deamon

● -v /var/docker/redis:/data → mount directories

● -p 6379:6379 → forward ports

Watch it!Watch it!

$ docker ps

Prints out information about docker containers

Watch it!Watch it!

$ docker ps -a

Prints out information about all docker containers:

● Running● Exited

Watch it!Watch it!

$ docker logs -t --follow romantic_enstein

Get logs from stdin/stdout of container

● -t → show timestamp● --follow → similar to

tail -f

Watch it!Watch it!

$ docker inspect romantic_enstein

Get info about container

● Environment variables

● Ports● Links

Enter Enter inside!inside!

- nsenter

- ssh

● nsenter uses namespaces

● Ssh needs ssh server inside

Tidy upTidy up- docker rm <container_id>

- docker rmi <image_id>

● Docker images use lots of space

● Docker images can clog all your available space on server (no more pulling from registry)

Tidy upTidy up$ docker ps -a | grep 'Exited' | awk '{print $1}' | xargs docker rm

● Get ids of exited containers● Remove containers with given ids

Repository Repository workflowworkflow● docker diff <container_id>● docker commit

<contaner_id> attero/stuff:my-tag

● Versioning!● Tags● Multiple versions● Push & pull

What we learned so farWhat we learned so far

Repository workflow– Pull

– Commit

– Push

Tidying up after containers– Rm

– Rmi

Monitoring– Ps

– Logs

– Inspect

– Top

Running containers– Interactive

– Deamon

– Mounting

– Forwarding

Containers are nice

How about automation?

DOCKERFILE

DOCKERFILE

- Version control- Automation- Portability

DOCKERFILE

FROM ubuntu

MAINTAINER [email protected]

# Install tmuxRUN \ apt-get update && apt-get install tmux

RUN mkdir /home/hello

# Define working directory.WORKDIR /home/hello

# Define default command.CMD ["/bin/bash"]

DOCKERFILE

FROM ubuntu ← defines base imag

MAINTAINER [email protected] ← who is reponsible

# Install tmuxRUN \ apt-get update && apt-get install tmux

RUN mkdir /home/hello ← let's run some commands

# Define working directory.WORKDIR /home/hello ← let's start here

# Define default command.CMD ["/bin/bash"] ← default command to run without arguments in run

DOCKERFILE

Every command in Dockerfile is run on a different container

DOCKERFILE

Don't start services in dockerfile.

DOCKERFILE

Cache!- use it- save lots of time- not changed layers are reused

DOCKERFILE

- short- good base image- most changing things at the bottom

DOCKERFILE

Every command in Dockerfile is run on a different container

Learning resources

● http://docs.docker.com/#installation-guides● http://docs.docker.com/reference/builder/● http://docs.docker.com/reference/commandline/cli

/● https://crosbymichael.com/dockerfile-best-practic

es.html● http://docs.docker.com/articles/basics/● https://www.youtube.com/watch?v=XCVOxht34H

s● https://www.youtube.com/watch?v=9bvdc55xYdo

More Learning resources

● https://www.digitalocean.com/community/tutorials/docker-explained-how-to-containerize-python-web-applications

● http://phusion.github.io/baseimage-docker/● https://circleci.com/docs/docker● http://docs.docker.com/userguide/usingdocker/

Q&A