Docker for Rails Developers

Building Our Image

The process of generating an image from a Dockerfile is called building an image. We do that with the docker build command, which has the following format:

$ docker build [options] path/to/build/directory

In our case, you should already still be in the directory containing our Dockerfile and project files so we can use a single dot to indicate the current directory. Let’s give it a go:

$ docker build .
Sending build context to Docker daemon  138.8kB
Step 1/6 : FROM ruby:2.6
 ---> f28a9e1d0449
Step 2/6 : RUN apt-get update -yqq
 ---> Running in 29677ed71d2b
Removing intermediate container 29677ed71d2b
 ---> 761da319d69a
...
Step 6/6 : RUN bundle install
 ---> ...