00-docker-basics

Docker Workshop - Docker Basics

This section is separated in:

• CLI Basics
• Dockerfile basics

CLI Basics

Version

Check you have latest version of docker installed:

docker version

• If you don't have docker installed, check here
• If you're not on the latest version, it will prompt you to update
• If you're not on docker group you might need to prefix commands with sudo. See here for details about it.

Commands

Check the available docker commands

docker

• Whenever you don't remember a command, just type docker
• For more info, type docker help COMMAND (e.g. docker help run)

RUN a "Hello World" container

docker run alpine echo "Hello World"

• If the Image is not cached, it pulls it automatically
• It prints Hello World and exits

RUN an interactive Container

docker run -it alpine sh
  cat /etc/os-release

• -i: Keep stdin open even if not attached
• -t: Allocate a pseudo-tty

RUN a Container with pipeline

cat /etc/resolv.conf | docker run -i alpine wc -l

SEARCH a Container

docker search -s 10 nginx

• -s: Only displays with at least x stars

RUN a Container and expose a Port

On Linux:

docker run -d -p 4000:80 nginx
google-chrome localhost:4000

On Mac:

docker run -d -p 4000:80 nginx
open "http://$(docker-machine ip default):4000"

• -d: Detached mode: Run container in the background, print new container id
• -p: Publish a container's port to the host (format: hostPort:containerPort)
• For more info about the container, see nginx

RUN a Container with a Volume

NOTE: Make sure to be on Docker Workshop directory since we'll use volume mounts in the containers of directories of the repository.

On Linux:

docker run -d -p 4001:80 -v $(pwd)/code/hello-world/site/:/usr/share/nginx/html:ro nginx
google-chrome localhost:4001

On Mac:

docker run -d -p 4001:80 -v $(pwd)/code/hello-world/site/:/usr/share/nginx/html:ro nginx
open "http://$(docker-machine ip default):4001"

• -v: Bind mount a volume (e.g., from the host: -v /host:/container, from docker: -v /container)
• The volume is linked inside the container. Any external changes are visible directly inside the container.
• This example breaks the immutability of the container, good for debuging, not recommended for production (Volumes should be used for data, not code)

Exercise 1 (10 mins)

• Build a static website
• Run it on your machine
• Share your (non-localhost) url on Slack

Dockerfile Basics

BUILD a Git Client Container

Create a Git Container manually:

docker run -it --name git alpine sh
  apk --update add git
  git version
  exit
docker commit git docker-git
docker rm git
docker run --rm -it docker-git git version
docker rmi docker-git

• --name: Assign a name to the container
• commit: Create a new image from a container's changes
• rm: Remove one or more containers
• rmi: Remove one or more images
• --rm: Automatically remove the container when it exits

Create a Git Container with Dockerfile:

cd code/docker-git
docker build -t docker-git .
docker run -it docker-git git version

• build: Build an image from a Dockerfile

code/docker-git/Dockerfile

FROM alpine:3.3
RUN apk update
RUN apk add git

• The FROM instruction sets the Base Image for subsequent instructions
• The RUN instruction will execute any commands in a new layer on top of the current image and commit the results

BUILD an Apache Server Container

Create an Apache Server Container with Dockerfile:

cd code/docker-apache2
docker build -t docker-apache2 .
docker run -d -p 4003:80 docker-apache2

On Linux:

google-chrome localhost:4003

On Mac:

open "http://$(docker-machine ip default):4003"

code/docker-apache2/Dockerfile

FROM alpine:3.3
RUN apk --update add apache2 && rm -rf /var/cache/apk/*
RUN mkdir -p /run/apache2
EXPOSE 80
CMD httpd -D FOREGROUND

• The EXPOSE instructions informs Docker that the container will listen on the specified network ports at runtime
• The CMD instruction sets the command to be executed when running the image

BUILD a Static website Image

cd code/hello-world
docker build -t hello-world .
docker run -d --name hello -P hello-world

On Linux:

google-chrome $(docker port hello 80)

On Mac:

open "http://$(docker-machine ip default):${$(docker port hello 80)##*:}"

• -P: Publish all exposed ports to the host interfaces
• port: Lookup the public-facing port that is NAT-ed to PRIVATE_PORT

code/hello-world/Dockerfile

FROM nginx:1.8-alpine
ADD site /usr/share/nginx/html

• The ADD instruction will copy new files from and add them to the container's filesystem at path

Exercise 2 (10 mins)

• Build your website with Dockerfile
• Run an instance
• Share your (non-localhost) url on Slack

PUSH Image to a Registry

For this step, we'll need to launch a registry:

docker run -d -p 5000:5000 --name registry registry:2

Then tag your image under the registry namespace and push it there:

REGISTRY=localhost:5000
docker tag hello-world $REGISTRY/$(whoami)/hello-world
docker push $REGISTRY/$(whoami)/hello-world

• tag: Tag an image into a repository
• push: Push an image or a repository to a Docker registry server

Exercise 3 (10 mins)

• Push your website to the local Registry (use your github username)
• Push your website image
• Share your image name on Slack

PULL Image from a Repository

docker pull $REGISTRY/$(whoami)/hello-world
docker run -d -P --name=registry-hello $REGISTRY/$(whoami)/hello-world

On Linux:

google-chrome $(docker port registry-hello 80)

On Mac:

open "http://$(docker-machine ip default):${$(docker port registry-hello 80)##*:}"

• pull: Pull an image or a repository from a Docker registry server

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Credits

This workshop was prepared by harbur.io, under MIT License. Feel free to fork and improve.