- Pull the Ruby container docker pull ruby:alpine - Start a container docker run -it --rm ruby:alpine /bin/sh - Now we can verify version of Ruby in the container ruby -v - To mount current folder to code folder to Ruby container, we can run below command: docker run -it --rm -v .:/code ruby:alpine /bin/sh - To start Ruby on Rails container, we can run below command: docker run -it --rm -p 3000:3000 -v .:/code mydockeruniversity/blog-rubyonrails /bin/sh - Now update gem gem update --system 3.4.22