Docker Practice

Setup

1. Fork this repository.

2. Open your fork in a GitHub Codespace.

3. Within the Codespace, install the necessary Python packages:

   pip install -r requirements.txt
   

4. Verify your software is installed by running the streamlit command. If that fails, pip uninstall streamlit and then install it again.

Write an App

5. Modify / update your code as desired.

6. To preview your app:

   streamlit run app.py
   

7. View your app via the open port. Repeat this process as necessary as you edit your app.

Containerize your App

8. Review the contents of Dockerfile and edit as necessary.

9. To build your container image:

   docker build -t SOMENAME .
   

10. Debug as necessary.

11. If you are building a container to be shared, you need to TAG it properly for the container registry you will use. I recommend the GitHub Container Registry, which uses this form of tag:

    docker build -t ghcr.io/ACCOUNT/IMAGE-NAME:TAG-NAME
    

12. (Optional) If you are building a container to share or run elsewhere, you must now push it to the registry:

    docker push ghcr.io/ACCOUNT/IMAGE-NAME:TAG-NAME
    

    Generally, in order to push to a registry you must first log into that registry through docker:

    docker login
    # logs you into the Docker Hub
    
    docker login ghcr.io
    # logs you into the GitHub Container Registry
    

Run your Container

1. There are two modes of running a container:

   • docker run -d - detached mode
   • docker run -it - interactive/TTY mode

   docker run -d -p 8080:80 nginx
   # runs a service independently from your shell.
   

   docker run -it ubuntu /bin/bash
   # requires you pass in a command to run
   docker run -it ubuntu date
   docker run -it ubuntu whoami
   

2. Map ports as needed. To map a port, use the -p flag. The host machine's port is to the left of the : and the container port is to the right:

   docker run -d -p 8080:80 nginx
   

   You could now open a browser (if working on your own laptop) to http://127.0.0.1:8080/ to preview your app. Or use the opened port in your GitHub Codespace.

3. Inject ENV variables as needed. This is a KEY-VALUE mapping using the -e flag:

   docker run -d -e MYKEY="somevalue" MY-IMAGE
   

4. Mount storage volumes as needed. This is a mapping of a host directory path to the left of the colon and the container path to the right, using the -v flag:

   docker run -d -v /home/data1:/mnt/data1 MY-IMAGE
   

Work with your Containers

List

To view all running containers:

$ docker ps
CONTAINER ID   IMAGE     COMMAND       CREATED      STATUS      PORTS     NAMES
7a60cfb1c377   ubuntu    "/bin/bash"   6 minutes ago   Up 6 days             priceless_bell

Stop

To stop a running container, find the container ID:

docker stop 7a60

Interact With

To effectively "shell" into an already-running container, use docker exec with the container ID of your target container. You must also give the process/command you want to run:

docker exec -it 7a60 /bin/bash

At this point you will be root "within" the container, and can inspect any logs, env values, etc. that you wish to.

Logs

To watch the stdout logs of your dockerized application:

docker logs 7a60

or

docker logs --follow 7a60

✅ Test Your Skills!

TRY THIS: Run a container in interactive mode, passing in an environment variable, while running a command that will print out that variable to the screen.