Docker

Table of Contents

Docker

Docker is a way to separate processes into what can be thought of as lightwieght virtual machines. It allows you to run processes in isolated containers. A docker ‘containter’ is a standalone package of software that will run reliably regardless of the computing environtment. Have you ever had the issue of a program working on your friend’s machine but not on yours? Giving everybody a well configured Docker container to run the program in can solve this problem. This is especially powerful when used to build software and applications, or to share content and colaborate with other developers. You can also add an extra level of secuirity by running a webapp through docker. If your webbapp is hacked, they will only have access to your docker container and not to your local machine.

Installation

  1. Update the apt package index and install necessary packages 
    sudo apt-get update
sudo apt-get install \
    ca-certificates \
    curl \
    gnupg \
    lsb-release
  2. Add Docker’s official GPA key 
    curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
  3. Set up the stable repository 
    echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
  4. Install the Docker Engine (hit enter when asked “Do you want to continue?”) 
    sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin
  5. Verify installation 
    sudo docker run hello-world

    This should present a message that begins with “Hello from Docker!”

Common Error

When trying to run your first docker, you might get this error:

docker: Got permission denied while trying to connect to the Docker daemon socket at...

If this happens, use the command sudo chmod 666 /var/run/docker.sock to change the permissions on the docker.sock file.

Lecture Videos

Lecture 1

On May 21, 2021 Prof Lundrigan discussed how to use Dockers. The video is embedded below.

Time Stamps

0:00 Introduction
1:20 What is Docker?
9:50 Terminology
11:50 ps
12:46 Run Ubuntu
22:00 Run Python
24:35 volumes
27:40 Docker Hub
29:29 Docker files
35:53 portainer
40:15 Build and run image from Dockerfile
46:24 Build Docker that runs as web app

Lecture 2

On May 20, 2022 Professor Lundrigan gave another lecture on Docker. The video is below.

Docker Cheat Sheet

Commands:

  • ps: print a list of the docker containers that are currently running
    • -a will also print containters that were created but are not currently running
  • run [image name]: creates a container
    • -it makes the container interactive
    • –rm will delete the container as soon as it is done running
    • -v [path/to/host/folder:/name_of_folder_in_container] allows you to access certain files from a container
    • -p [localport:containerport] maps port from the container to a port on your local machine to run the webapp
  • start [name]: restarts a previously created container
  • exec [command]: allows you to interact with containers that are running in the background
  • stop [name]: stops running a container
  • images: shows your repo of images
  • build: build an image from a dockerfile
    • -t tags the container for you

Conclusion

Docker is a powerful tool for developers to build, ship, and run applications. You can stage a standardized environment that can be easily set up and used across an organization, or a team of developers. It is excellent for finding and fixing bugs. You can execute the testing of an application in a Docker container, then make edits and relaunch your design when bugs are identified. This provides quick verification of your fixes and leads to an efficient developement process. Updates are then easy to distribute by pushing your new docker image to the production environment. The ability to easily set up isolated environments is perfect for use in continuous integration and continous deployment. There is also a wide variety of docker images and applications that you can take advantage of as a user. Check out some of these examples:

Activities

  • Run your csv_parser.py program in a docker container (you will need to create a container using -v to have the files you need)
  • Install portainer
  • Explore the portainer website, create a new image using portainer
  • Browse dockerhub and find a couple of cool images. Find the image layers of their latest version

Additional Resources