Docker by demo

Docker by Demoby Srikanth Seshachary

What is Docker?

History of LXC (Linux Containers)

cgroups

namespaces

Docker, a high level API

Why do we need Docker?

dependencies as versioned code

isolation of processes

speed

debugging

pluggability

devops – a process enforcer

devops – a tool between rpm, deb and ansible, chef, puppet

devops – a process enforcer

What’s wrong with VMs?

speed

new vm = minutes,new container = seconds

vms = separate kernel,containers = shared kernel (can have

different base image)

duplicate services (cron, syslog) need to be run for each role

Installing Docker

only 64-bit supported

kernel 3.8

sudo yum install docker-iosudo service docker start

Downloading (aka pulling) Images

$ sudo docker pull ubuntu$ sudo docker images

Launching Containers

$ sudo docker run -i -t ubuntu /bin/bash$ sudo apt-get install python3$ sudo docker ps$ sudo docker commit <container_id> image

Docker Repositories

local private images

The Docker Hub

Writing Your First Dockerfile

# DockerfileFROM ubuntuMAINTAINER James Turnbull "[email protected]"RUN apt-get updateRUN apt-get install -y nginxRUN echo 'Hi, I am in your container' \ >/usr/share/nginx/html/index.htmlEXPOSE 80ENTRYPOINT ["/usr/sbin/nginx"]CMD ["-h"]

$ sudo docker build -t="user/nginx" .

$ sudo docker run -t -i user/nginx

$ sudo docker run -t -i user/nginx -g "daemon off;“

$ sudo docker port <container>

Issues/Limitations/Misconceptions

lack of image inheritance– composing multiple images (for

example, ruby and nginx)

yet another tool – dockerizing your app takes time

not every app can be dockerized

you still need configuration management tools like ansible or

puppet

orchestration isn’t avoided either

Where do you go from here?

the docker book, james turnbull

try dockerizing one of your applications

References

• http://knitatoms.net/2013/12/benefits-of-docker-for-application-deployment/

• https://devopsu.com/blog/docker-misconceptions/

• https://stackoverflow.com/questions/16047306/how-is-docker-io-different-from-a-normal-virtual-machine