Useful notes about Docker

• Docker Products
  • Docker Engine
  • Docker Compose
  • Docker Swarm
  • Docker Machine
  • Docker CLoud
• Check your images and containers
  • List all your images
  • List all your containers
• Clean images and containers
  • Delete an image
  • Delete a container
  • Delete containers from a specific image
  • Nuclear Clean :)
    • Clean all containers
    • Clean all images
• Passing environment variables, ports and IP addresses
  • Example running a webapp
  • On which port is your webapp running?
  • Run shell commands from within a container
• Clean the volumes
  • List dangling volumes:
  • List all volumes:
  • Remove data within the volumes
• Docker Compose
  • Useful commands for Docker Compose
• Tag and Push your image to Dockerhub
• Load-balancing
• Links

Docker Products

The Docker platform is comprised of a family of tools and products.

List of guides:

• Docker for Mac
• Docker for Windows
• Docker for Linux
• Docker CLoud
• Docker for AWS
• Docker for Azure

Tools:

• Docker Tools
• Docker Machine

Docker Engine

When people say “Docker” they typically mean Docker Engine, the client-server application made up of the Docker daemon, a REST API that specifies interfaces for interacting with the daemon, and a command line interface (CLI) client that talks to the daemon (through the REST API wrapper). Docker Engine accepts docker commands from the CLI, such as docker run <image>, docker ps to list running containers, docker images to list images, and so on.

Docker Engine runs natively on Linux systems. If you have a Linux box as your primary system, and want to run docker commands, all you need to do is download and install Docker Engine. However, if you want an efficient way to provision multiple Docker hosts on a network, in the cloud or even locally, you need Docker Machine.

Docker Compose

• Overview Docker Compose

Docker Swarm

Functionality folded directly into native Docker, no longer a standalone tool.

• Overview Docker Swarm

Docker Machine

Use docker-machine to create, use and manage a Docker host inside of a local virtual machine.

• Docker Engine & Docker Machine
• Installation
• Get started with Docker Machine and a local VM

Docker CLoud

Manages multi-container applications and host resources running on a cloud provider (such as Amazon Web Services or Azure).

• About Docker Cloud

Check your images and containers

List all your images

docker images

List all your containers

docker ps -a

Clean images and containers

Delete an image

docker rmi <*your image id*>

Delete a container

docker rm <*your container id*>

Delete containers from a specific image

To remove all docker containers based on a specific image name, e.g. centos:7:

# Stop all containers with the given image name
docker ps -a | awk '{ print $1,$2 }' | grep centos:7 | awk '{print $1 }' | xargs -L1 docker stop

# Delete the same stopped containers
docker ps -a | awk '{ print $1,$2 }' | grep centos:7 | awk '{print $1 }' | xargs -I {} docker rm {}

Nuclear Clean :)

If you get an error like "no space left on device" and if you don't care about doing a nuclear clean, you can:

Clean all containers

docker-compose stop
docker ps -a | sed '1 d' | awk '{print $1}' | xargs -L1 docker rm

Clean all images

Again, careful when using such commands, do not use it in production. The great thing is that if you have your Dockerfile(s), it's easy to rebuild and or docker pull.

docker-compose stop
docker images -a | sed '1 d' | awk '{print $3}' | xargs -L1 docker rmi -f

Passing environment variables, ports and IP addresses

Example running a webapp

$ docker run --name static-site -e AUTHOR="Your Name" -d -P dockersamples/static-site

You can also run a second webserver at the same time, specifying a custom host port mapping to the container's webserver.

$ docker run --name static-site-2 -e AUTHOR="Your Name" -d -p 8888:80 dockersamples/static-site

In the above command:

`-d` will create a container with the process detached from our terminal
`-P` will publish all the exposed container ports to random ports on the Docker host
`-e` is how you pass environment variables to the container
`--name` allows you to specify a container name
`AUTHOR` is the environment variable name and Your Name is the value that you can pass

You can stop and remove the containers by their name

$ docker stop static-site
$ docker stop static-site-2
$ docker rm static-site
$ docker rm static-site-2

On which port is your webapp running?

docker port static-site

Run shell commands from within a container

$ docker ps -a
CONTAINER ID        IMAGE                     COMMAND                  CREATED             STATUS              PORTS                      NAMES
708609e11d30        flaskrecipeapp_web        "flask run --host=..."   36 hours ago        Up 2 hours          0.0.0.0:8000->8000/tcp     flaskrecipeapp_web_1
f8e456ef29c2        flaskrecipeapp_postgres   "docker-entrypoint..."   36 hours ago        Up 2 hours          0.0.0.0:5432->5432/tcp     flaskrecipeapp_postgres_1
590489d1c492        mlsuite_jupyter           "/bin/sh -c 'jupyt..."   4 days ago          Up 3 minutes        0.0.0.0:8899->8899/tcp     mlsuite_jupyter_1
69c232091e02        mlsuite_executionserver   "/bin/sh -c 'pytho..."   4 days ago          Up 3 minutes        0.0.0.0:4007->4007/tcp     mlsuite_executionserver_1
d397ba1e1435        mlsuite_modelserver       "/bin/sh -c 'pytho..."   4 days ago          Up 3 minutes        0.0.0.0:4001->4001/tcp     mlsuite_modelserver_1
b7ec18ee5cd1        mlsuite_doc               "nginx -g 'daemon ..."   4 days ago          Up 3 minutes        0.0.0.0:8123->80/tcp       mlsuite_doc_1
51ec9571292f        mongo:latest              "docker-entrypoint..."   2 weeks ago         Up 3 minutes        0.0.0.0:27017->27017/tcp   mongodb
$
$ sudo docker exec -i -t 590489d1c492 /bin/bash

Clean the volumes

Warning be very careful with this if you have some data you want to keep.

Additional commands:

List dangling volumes:

docker volume ls -qf dangling=true

List all volumes:

docker volume ls

Remove data within the volumes

docker volume rm $(docker volume ls -qf dangling=true)

Docker Compose

Getting Started guide: https://docs.docker.com/compose/gettingstarted/

Useful commands for Docker Compose

docker-compose up   # to start your services
docker-compose -d up   # to start your services in the background (in **detached** mode)
docker-compose stop   # Stop all of your services
docker-compose down --volumes   # Bring everything down (i.e. including the data volumes used by your services)

Tag and Push your image to Dockerhub

• List your docker images to find the ID of the image you want to push

docker images

• Tag your image using this ID, and check it has been tagged properly

docker tag 71df3012md... patrickmerlot/docker_demo:latest
docker images

• Create an account on Dockerhub if not done already, then login

docker login

• Push your image to DockerHub

docker push patrickmerlot/docker_demo

and your done! Check if it appears online: https://hub.docker.com/r/patrickmerlot/docker_demo/

Load-balancing

Get Started, Part 3: Services: scale our application and enable load-balancing. To do this, we must go one level up in the hierarchy of a distributed application: the service.

In a distributed application, different pieces of the app are called “services.”

Services are really just “containers in production.” A service only runs one image, but it codifies the way that image runs—what ports it should use, how many replicas of the container should run so the service has the capacity it needs, and so on. Scaling a service changes the number of container instances running that piece of software, assigning more computing resources to the service in the process.

Luckily it’s very easy to define, run, and scale services with the Docker platform – just write a docker-compose.yml file.

Links

• Docker samples
  • Create a Docker image for a Python Flask app
  • Deploying to a swarm: Docker Swarm allows you to run your containers on more than one machine
• Docker Compose getting-started guide: https://docs.docker.com/compose/gettingstarted/