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Docker Cheatsheet

Petit article mémo sur Docker

Getting Started

make sure that client can talk to engine + current version docker version

An image is the application we want to run. A container is an instance of the image running as a process.

Containers

docker container run —publish 80:80 nginx Left number == Host port. Make sure it’s not already used (otherwise bind error)

  1. Pull down “nginx” image from Docker Hub
  2. Started a new container accessible from that image.
  3. Opened port 80 on the host IP
  4. Routes that traffic to the container IP port 80.

Option —detach => Run in the background. docker container run —detach —publish 80:80 nginx

List all running containers

docker container ls == docker ps

Nommer un container

docker container run —detach —name LENOM —publish 13370:80 nginx

Voir les derniers logs d’un container

docker container logs nom_container

Voir les processus s’exécutant dans un container

docker container top nom_container

Ce qui se passe quand on run un container

Changing the defaults :

  • The listening port on the host
  • Change version of the image
  • Change CMD executed when the container runs on start

A container is a process running on your host environment system.

Run multiple containers

docker container run —detach —name nginx —publish 80:80 nginx docker container run —detach —name mysql —env MYSQLRANDOMROOT_PASSWORD=yes —publish 3306:3306 mysql docker container run —detach —name httpd —publish 8080:80 httpd

See what’s going on in containers

Process list in one container docker container top container_name

Details of one container config

docker container inspect container_name

Performance stats for all containers

docker container stats container_name

Getting a shell inside container

docker container run -it Start new container interactively T for terminal I to keep the session open

docker container exec -it Run additionnal command in a running container

Alpine is smaller than Ubuntu.

Publishing ports is always in HOST:CONTAINER format.

docker container run nginx use nginx:alpine instead !

Assignment - CLI App Testing

docker container run —rm -it —name centos centos:7 bash curl 7.29

docker container run —rm -it —name ubuntu ubuntu:14.04 bash curl 7.35

docker container run —detach -it —name centos centos:7 bash

Assignment - Round Robin

docker network create roundrobinnetwork

docker container run —detach —network roundrobinnetwork —net-alias search elasticsearch:2

docker container run —rm —net roundrobinnetwork alpine nslookup search

docker container run —rm —net roundrobinnetwork centos curl -s search:9200

Container Images

An image is made of app binaries and dependencies. Metadata about the image data and how to run the image. Not a complete OS. No kernel, kernel modules. Small as one file (app binary) like golang. Big as Ubuntu with apt, apache, PHP and more installed.

Docker Hub

docker pull nginx docker pull nginx:1.10.11 Always use a specific version to prevent software from updating automatically using latest tag. Docker Hub = The apt package system for containers Alpine => Smaller than counterparts OS.

Docker Image Layers

docker history mysql View changes on the image. When we download an image, we start with one layer. In a dockerfile, we can add more stuff using apt-get or env variables : it adds a new layer everytime. Each layer is uniquely identified and only stored once on a host. Save storage space.

Image Tagging and Pushing to Docker Hub.

Images don’t have name. We refer to them using repository, tag. Tag => Pointer to a specific image commit.

Add tag to existing image: docker image tag SOURCEIMAGE:TAG TARGETIMAGE:TAG

docker image push bretfisher/nginx.

Dockerfile basics

&& => Make sure these commands are run for one layer. CMD => final command that will be run after container is launched or restarted.

Running Docker Builds

At the top => things that change the least At the bottom => things that change the most

Extending official images

WORKDIR => cd pour se placer dans un répertoire.

Assignment: Build Your Own Image with a Dockerfile

Dockerfile are part process workflow and part art. docker image build -t node-app . docker container run -p 3000:80 —rm node-app

Container Lifetime and Persistent Data

Containers are usually immutable and ephemeral. Temporary and disposable. Volumes need manual deletion.

Use friendly name for volumes to see which volumes is attached to which container. docker container run -d —name mysql -e MYSQLALLOWEMPTYROOTPASSWORD=true -v mysql-database:/var/lib/mysql mysql

If we need to specify the driver, we need to create the volume ahead of container creation.

Partager dossier courant pour live modifs docker container run -d —name nginx -p 80:80 -v $(pwd):/usr/share/nginx/html nginx

Assignment - Named Volumes

docker container run -d —name postgres -v pgsql-data:/var/lib/postgresql/data postgres:9.6.1

docker container logs postgres

docker container stop postgres

docker container run -d —name postgres2 -v pgsql-data:/var/lib/postgresql/data postgres:9.6.2

Assignment - Bind Mounts

Super cool for local development.

docker run -p 80:4000 -v $(pwd):/site bretfisher/jekyll-serve

Docker Compose

Configure relationships between containers Save our docker container run settings in easy-to-read file. Create one-liner developer environment startups.

We specify in that file the containers we need to run …

docker-compose.yml

depends_on : explique les dépendances entre containers au yaml

docker-compose up # setup volumes networks and start all containers

docker-compose down # stop all containers and remove containers / volumes / networks

docker-compose logs to see logs, -d detach to run in background.

docker-compose ps , top, down.

Assignment - Writing a compose file

use the service name as the DNS name. localhost won’t work. use name. Volumes are never removed automatically.