ABCs of Docker

● Basics of container and Docker● Major Docker components● Starting learning basic docker commands● Hands-on labs and exercises● Quiz

Course outline

Prerequisites

● Basic knowledge of how OS works, no need to be expert

● At least 1 virtual machine

Traditional application deployment

A bit of scale makes a bit of scare

Containers under the hood

cgroups - Wikipedia

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.Engineers at Google (primarily Paul Menage and Rohit Seth) started the work on this feature in 2006, under the name "process containers".[1] In late 2007 the nomenclature changed to "control groups" due to the confusion caused by multiple meanings of the term "container" in the Linux kernel context, and control-group functionality merged into kernel version 2.6.24.[2] Since then, developers have added many new features and controllers, such as support for kernfs,[3] firewalling,[4] and unified hierarchy.[5]

Quiz - Containers

What are the benefits of using container instead of VM?● No need for hypervisor● No need for operating system● No physical hardware● No need for priveleged user● No. It’s uselles.

I create process with PID=1234 in container. What PID will be on host OS?a. the same as in container: PID=1234b. on host there will be PID=4321 that maps to PID=1234

in containerc. it wont be created in container. Actually container

creates it on host.d. there will be no pid on host. PID=1234 is the child

process in container

Quiz - Containers

What are the main components of namespaces?a. uts, ipc, pid, network, user, mountb. user, pid, mount, filesystem, application, ioc. pid, os, hardware, user, internet, filesystemd. mount, hardware, network, user, pid, cgroup

Quiz - Containers

Quiz - Containers

What should i do to run application with unprivileged user in container?a. change the owner to current user and run itb. login as sudo and run the applicationc. enter the container and run itd. login as sudo then chown the application then run it

Major Docker components

In short: write once, really run anywhere

Docker images and containers

pull the image from docker cloud servers

Images repository - Dockerhub

Installing Docker engine

1. Open https://docs.docker.com/installation/

2. Find the name of your host operating system from the list

3. Follow the instructions

https://docs.docker.com/installation/

Linux: Add current user to docker group

sudo gpasswd -a <user_name> docker

Mac OS: set env variables for boot2docker

boot2docker up

export DOCKER_HOST=tcp://192.168.59.103:2376export DOCKER_CERT_PATH=<cert path>export DOCKER_TLS_VERIFY=1or $(boot2docker shellinit)

Get ip of boot2docker: boot2docker ipCheck version of docker: docker version

Windows: maybe like on MacOS...but didnt try

boot2docker up

set DOCKER_HOST=tcp://192.168.59.103:2376set DOCKER_CERT_PATH=<cert path>set DOCKER_TLS_VERIFY=1or boot2docker shellinit

Get ip of boot2docker: boot2docker ipCheck version of docker: docker version

Let docker say: Hello World!

docker run hello-world

Now let’s get into the container

1) docker pull centos – fetch centos image from repository2) docker run centos – run fetched centos image within container3) docker ps - list the running containers4) docker ps -a - list all the containers (running + not running)5) docker exec - to execute the command inside container6) docker attach - get into the container7) exit from container quits the container8) Ctrl+P and Ctrl+Q leaves the running container9) docker inspect <container_id> - show info about running container

Lab: Run required container

IOS/Android developers:1) docker run -d –p 8080:8080 jenkins2) Open http://<docker_host>:8080 in your browser and create build plan in

jenkins

Service developers:3) docker run -it --rm williamyeh/scala4) Write hello world in scala

TIP: docker --help is you cheat sheet

Quiz - Docker

What is the difference between images and containers?a. containers consist of binary files, images consist of user app filesb. containers run only once, whereas images run multiple timesc. containers pulled from dockerhub, whereas images stores locallyd. images consist of instructions and user files, whereas containers

only runtime environment for user process

Quiz - DockerWhat will be the result of the following instructions?docker run -it my-image /bin/bash # let’s say it returns ID 123...echo “Sample text” | cat > SampleText.txtexitdocker cp 123:/root/SampleText.txt ./

a. will copy SampleText.txt to current directoryb. will copy data from the current directory to /root/SampleText.txt inside containerc. prints to screen Sample text and copies SampleText.txt to current directory on docker hostd. does nothing. Terminates with error

Quiz - DockerWhat will be the result of the following instructions?docker run -d my-image /bin/bash echo “Sample text” | cat > SampleText.txt # let’s say returns id 123...docker run -d my-image /bin/bash “ping 8.8.8.8” docker cp 123:/root/SampleText.txt ./

a. will copy SampleText.txt to current directoryb. will copy data from the current directory to /root/SampleText.txt inside containerc. prints to screen Sample text and copies SampleText.txt to current directory on docker hostd. does nothing. Terminates with error

Writing own Dockerfile

FROM ubuntu:latestMAINTAINTER <name surname>FROM ubuntu:latestRUN apt-get updateRUN apt-get install -y nginxCMD ["nginx", "-g", "daemon off;"]

mailto:[email protected]

Docker Workflow 1

1) Download file from curl -L -O http://github.com/atbaker/flask-example/archive/master.zip2) Unzip master.zip3) run python flask-example.py

Build as docker:

FROM python:2-onbuildEXPOSE 8000CMD [“gunicorn”, “-c”, “gunicorn_config.py”, “flask-example:app”]

Docker Workflow 2

Download file from curl -L -O http://github.com/atbaker/django-example/archive/master.zip

Build as docker:

FROM python:2.7-onbuildEXPOSE 8000CMD [“gunicorn”, “-c”, “gunicorn_config.py”, “--chdr”, “django-example”, “wsgi:application”]

docker run --name postgres -d postgres:9.3docker run --name memcached -d atbaker/memcached-verbosedocker run --name django -d -p 8000:8000 --link postgres:db --link memcached:cache django-exampledocker run --name django --link postgres:db --link memcached:cache django-example python django/example/manage.py migrate

Docker workflow 2 with Docker-Compose

django: build: . links:

- postgres:db- memcached:cache

ports:- “8000:80”

postgres: image:postgres:9.3

memcached: image:atbaker/memcached-verbose

Useful resources

https://docs.docker.com/ - official docs from Dockerhttps://docs.docker.com/compose/ - official docs about Docker Composehttps://docs.docker.com/docker/introduction/understanding-docker/ - Docker architecturehttps://linuxcontainers.org/ - WiKi about Linux Containers (LXC)https://lwn.net/Articles/531114/ - Linux namespaces overviewhttps://lwn.net/Articles/532748/ - Linux PID namespaces

https://docs.docker.com/

https://docs.docker.com/

https://docs.docker.com/compose/

https://docs.docker.com/compose/

https://docs.docker.com/docker/introduction/understanding-docker/

https://docs.docker.com/docker/introduction/understanding-docker/

https://linuxcontainers.org/

https://linuxcontainers.org/

https://lwn.net/Articles/531114/




ABCs of Docker

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