Building and pushing Docker images to Docker Hub

1# We're currently using Ruby 2.5.1
2FROM ruby:2.5.1-alpine
3
4# Always nice to know who to contact
5LABEL maintainer="niall@absolutedevops.io"
6
7# In a single step - install the dependences (apk is Alpine Linux's 
8# equivalent to apt) and then remove the cached files (to keep the image 
9# as small as we can)
10RUN apk add --update bash build-base nodejs mariadb-dev tzdata && \
11  rm -rf /var/cache/apk/*
12
13# Make a directory to hold our app and set the working directory to it
14RUN mkdir /app
15WORKDIR /app
16
17# Do the gem installation stuff first, in a separate step, because they
18# Don't change as often as the code (so we can cache them in a separate 
19# Docker image layer)
20COPY Gemfile Gemfile.lock ./
21RUN bundle install --binstubs
22
23# Now copy the current folder to the WORKDIR and drop root privileges
24COPY . .
25RUN chown -R nobody:nogroup /app
26
27# Compile all assets
28RUN bundle exec rake assets:precompile
29
30# Inform Docker what port our container listens on at runtime
31EXPOSE 3000
32
33# Set a default command to start the Rails server (can override this for workers, etc.)
34CMD ["bundle", "exec", "rails", "server", "-p", "3000"]

1docker build -t <your_username>/k8s-sample-app:v0.1 .

1$ docker images
2REPOSITORY                               TAG                 IMAGE ID            CREATED             SIZE
3<your_username>/k8s-sample-app           v0.1                104edfbbe440        2 minutes ago       617MB

1docker login
2# enter Docker Hub username and press enter
3# enter Docker Hub password and press enter

1docker push <your_username>/k8s-sample-app:v0.1

1docker build -t <your_username>/k8s-sample-app:v0.2 .
2docker push <your_username>/k8s-sample-app:v0.2