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Docker Workshop - Docker Basics

Sections:

Docker Command Line

Version

Check that you have latest version of docker installed with the command:

$ docker version
  • If you do not have docker installed, check Docker Installation
  • Docker will prompt you to update if you don't have the latest version
  • If you're not on docker group you might need to prefix commands with sudo.
  • See Root Access for Linux for details about this.

Commands

Check the available docker commands

$ docker
  • Type docker to see all available docker commands
  • For more info, type docker help $DOCKER_COMMAND (e.g. docker help info)

"Hello World" Docker container

docker run alpine echo "Hello World"

$ docker run alpine echo "Hello World"
Unable to find image 'alpine:latest' locally
latest: Pulling from library/alpine
88286f41530e: Already exists
Digest: sha256:1072e499f3f655a032e88542330cf75b02e7bdf673278f701d7ba61629ee3ebe
Status: Downloaded newer image for alpine:latest
Hello World

Notice that if the docker image doesn't exist that docker will pull the image for you

This docker image merely prints the text Hello World and then exits

Interactive Container

$ docker run -it alpine sh
/ # cat /etc/host
hostname  hosts
/ # cat /etc/hostname
6152fd2650a9

Notice that the docker container shell is in the root path /

Docker commandline options for run

  • -i, --interactive Keep STDIN open even if not attached
  • -t, --tty Allocate a pseudo-TTY

Container with a pipeline

$ echo "banana" "apples" "tomatoes" "\n" "burger" | docker run -i alpine wc -l
2

Searching a container

$ docker search -s 5 alpine
Flag --stars has been deprecated, use --filter=stars=3 instead
NAME                           DESCRIPTION                                     STARS     OFFICIAL   AUTOMATED
alpine                         A minimal Docker image based on Alpine Lin...   2353      [OK]
anapsix/alpine-java            Oracle Java 8 (and 7) with GLIBC 2.23 over...   219                  [OK]
frolvlad/alpine-glibc          Alpine Docker image with glibc (~12MB)          86                   [OK]
container4armhf/armhf-alpine   Automatically built base images of Alpine ...   67                   [OK]
davidcaste/alpine-tomcat       Apache Tomcat 7/8 using Oracle Java 7/8 wi...   19                   [OK]

Docker commandline options for search

  • -s $DOCKER_AMOUNT Displays at least $DOCKER_AMOUNT of results

Run container and expose port

Linux:

docker run -d -p 3002:80 nginx
google-chrome localhost:3000

OS X:

docker run -d -p 3002:80 nginx
open "http://$(docker-machine ip default):3000"

*If you run into issues with this command do the following: 

$ docker-machine stop default
$ docker-machine ip default

$ docker-machine start default
Starting "default"...
(default) Check network to re-create if needed...
(default) Waiting for an IP...
Machine "default" was started.
Waiting for SSH to be available...
Detecting the provisioner...
Started machines may have new IP addresses. You may need to re-run the `docker-machine env` command.
$ eval "$(docker-machine env default)"
$ docker-machine env
export DOCKER_TLS_VERIFY="1"
export DOCKER_HOST="tcp://192.168.99.100:2376"
export DOCKER_CERT_PATH="/Users/marcelbelmont/.docker/machine/machines/default"
export DOCKER_MACHINE_NAME="default"

# Run this command to configure your shell:
# eval $(docker-machine env)
$ docker run -d -p 3002:80 nginx
Unable to find image 'nginx:latest' locally
latest: Pulling from library/nginx
e6e142a99202: Pull complete
c5b776fbdd26: Pull complete
1128674f0003: Pull complete
Digest: sha256:8e2645484fe09122ea8aef7a186658082a860312d47fa51675cbf21d1b4b901a
Status: Downloaded newer image for nginx:latest
6bd06e4427580752b350c49fce64414a635cb816b395ab5832c41b6204980628

$ open "http://$(docker-machine ip default):3002"

Docker commandline options for run

  • -d, --detach Run container in background and print container ID
  • -p, --publish list Publish a container's port(s) to the host
  • For more info about the container, see nginx

Nginx Success

Docker container with a volume

NOTE: You should cd docker-workshop since we will be using volume mounts in the containers in this repo.

You will need to stop the process running in port 3002 currently

$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                  NAMES
6bd06e442758        nginx               "nginx -g 'daemon ..."   43 minutes ago      Up 43 minutes       0.0.0.0:3002->80/tcp   affectionate_hawking

$ docker stop 6bd06e442758
6bd06e442758

On Linux:

docker run -d -p 3002:80 -v $(pwd)/docker-workshop/hello-world/site/:/usr/share/nginx/html:ro nginx
google-chrome localhost:3002

OS X:

$ docker build -t helloworld
$ docker run -d -p 3002:80 -v $(pwd)/code/hello-world/site/:/usr/share/nginx/html:ro nginx
$ open "http://$(docker-machine ip default):3002"

Stepping into the Running Container

$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED              STATUS              PORTS                  NAMES
14d304726a06        nginx               "nginx -g 'daemon ..."   About a minute ago   Up About a minute   0.0.0.0:3002->80/tcp   keen_heyrovsky

$ docker exec -it 14d304726a06 /bin/sh

# cd /usr/share/nginx/html

# cat index.html
  • -v, --volume list Bind mount a volume (HOST:CONTAINER)
  • The volume is linked inside the container. Any external changes are visible directly inside the container.
  • Remember though that volumes are to be used for data, not code

Exercise

  • Build a static website similar to the hello world example
  • Run it on your machine

Dockerfile Basics

Building a Git Client Container

Create a Git Container manually:

$ docker run -it --name git alpine sh
# apk --update add git
# git version
# exit

Commit the docker container:

$ docker commit git docker-git
a1a4c66165227d2222070febaf6431402bd0ba8dc4ee69a156072cae9ec5dbe2

$ docker rm git
git

$ docker run --rm -it docker-git git version
git version 2.13.0

$ docker rmi docker-git
Untagged: docker-git:latest
Deleted: sha256:a1a4c66165227d2222070febaf6431402bd0ba8dc4ee69a156072cae9ec5dbe2
Deleted: sha256:6717e3e65ffaf33d3872c24a896542dea9903a52bd9f8b1e7f063fc3ee658fde
  • docker run --name string Assign a name to the container
  • docker commit Create a new image from a container's changes
  • docker rm Remove one or more containers
  • docker rmi Remove one or more images
  • docker run --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
  • docker build Build an image from a Dockerfile

code/docker-git/Dockerfile

FROM alpine:3.5
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

Docker 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 3003:80 docker-apache2

Linux:

google-chrome http://localhost:3003

OS X:

open http://localhost:3003

code/docker-apache2/Dockerfile

FROM alpine:3.5
RUN apk --update add apache2 && rm -rf /var/cache/apk/*
RUN mkdir -p /run/apache2
EXPOSE 80
CMD httpd -D FOREGROUND

Expose Command in Dockerfile

  • The EXPOSE instruction informs Docker that the container listens on the specified network ports at runtime.

CMD Command in Dockerfile

The CMD instruction has three forms:

  1. CMD ["executable","param1","param2"] (exec form, this is the preferred form)
  2. CMD ["param1","param2"] (as default parameters to ENTRYPOINT)
  3. CMD command param1 param2 (shell form)

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 Publish all exposed ports to random ports
  • docker port List port mappings or a specific mapping for the container

code/hello-world/Dockerfile

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

ADD Command in Dockerfile

ADD has two forms:

  1. ADD ...
  2. ADD ["",... ""] (this form is required for paths containing whitespace)

Exercise

  • Build your website with Dockerfile
  • Run an instance

Push Docker image to registry

Docker Registry

Launching a registry:

$ docker run -d -p 4000:4000 --name registry registry:2
Unable to find image 'registry:2' locally
2: Pulling from library/registry
90f4dba627d6: Pull complete
3a754cdc94a5: Pull complete
0756a217635f: Pull complete
f82b9495c796: Pull complete
154ef19ddee6: Pull complete
Digest: sha256:5eaafa2318aa0c4c52f95077c2a68bed0b13f6d2b464835723d4de1484052299
Status: Downloaded newer image for registry:2
f7f9be850b0f5e7c3ef741a9bfdd9e7c6df7e10b29cc641e55b318dfdd82a931

Tag Docker image under the registry namespace and push it:

$ cd code/hello-world
$ docker build -t hello-world .
Sending build context to Docker daemon  5.632kB
Step 1/2 : FROM nginx:1.8-alpine
 ---> c0dddb65129b
Step 2/2 : ADD site /usr/share/nginx/html
 ---> Using cache
 ---> 37e37aa0cac0
Successfully built 37e37aa0cac0

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

*this command could fail*

If it fails then do the following below

$ docker login
$ docker tag hello-world jbelmont/hello-world
$ docker push jbelmont/hello-world
The push refers to a repository [docker.io/jbelmont/hello-world]
62bf6ff9568c: Pushed
5f70bf18a086: Mounted from library/nginx
55b35a1a5cd1: Mounted from library/nginx
b7c1623f5bfc: Mounted from library/nginx
b96a0a302d98: Mounted from library/nginx
c56b7dabbc7a: Mounted from library/nginx
latest: digest: sha256:e297cc2cf9ce018a2f90e9febfcc199444d4dc31cbcbada9417b328a20f63cd1 size: 2596

Read Moby Github issue

  • docker tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  • docker push Push an image or a repository to a registry

Exercise

  • Push your website to the local Registry (use your github username)
  • Push your website image

Pulling Docker Image from a Repository

$ docker pull jbelmont/hello-world
Using default tag: latest
latest: Pulling from jbelmont/hello-world
Digest: sha256:e297cc2cf9ce018a2f90e9febfcc199444d4dc31cbcbada9417b328a20f63cd1
Status: Image is up to date for jbelmont/hello-world:latest

docker run -d -P --name=registry-hello jbelmont/hello-world

On Linux:

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

Hello World Docker Image

On Mac:

open "http://$(docker-machine ip default):${$(docker port registry-hello 80)##*:}"
  • docker pull Pull an image or a repository from a Docker registry server

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