Dockerfile Creation and Explanation
Explore how to create a functional Dockerfile for a Rails application by using key Dockerfile instructions such as FROM to base the image, RUN to execute commands, COPY to include app files, and WORKDIR to set the working directory. Understand how each instruction contributes to building an efficient image that packages all necessary components to run your Rails app.
Dockerfile for Rails app
A Dockerfile is made up of various instructions such as FROM, RUN, COPY, and WORKDIR, each capitalized by convention. Let’s look at a specific example.
Here is a basic Dockerfile for running our Rails app.
FROM ruby:2.7
RUN apt-get update -yqq
RUN apt-get install -yqq --no-install-recommends nodejs
COPY myapp /usr/src/app/
WORKDIR /usr/src/app
RUN bundle install
Every image has to start from another, preexisting image. For that reason, every Dockerfile begins with a FROM instruction, which specifies the image to be used as its starting point. Typically, we will look for a starting image that is close to what we need but more general. That way we can extend and customize it to our needs.
Dockerfile explanation
FROM instruction
The first line of our Dockerfile is:
FROM ruby:2.7.2
This is saying that our image will be based on the ...