To create a new docker image a good stratagy is to start with:
docker run -it –entrypoint “/bin/bash” ubuntu:20.04
This will start an interactive ubuntu basic docker image.
You can then install what you need and make a note of how you do it. For example you might need to run apt-get update and apt-get install for some basic programs such as wget.
You can then use the notes you have made into your docker file. By adding the commands you ran into ‘RUN’ statements in your docker file.
For Heroku, install and signup.(https://devcenter.heroku.com/articles/container-registry-and-runtime)
Then navigate to a dir and run
heroku create
heroku container:push web (you may need to do -a and the app name if you have more than one docker file in the repo as this repo does)
heroku container:release web (maybe -a appname)
heroku open (maybe -a appname)