Creating Images for Testing with Postgres Database

This is based on: https://nickjanetakis.com/blog/docker-tip-79-saving-a-postgres-database-in-a-docker-image

For testing purposes, you may want one or more "staged" containers with your data in various configurations. For example, you might want an empty container with just your database and schema created, and another with some sample data.

Your tests can start with a clean-slate version of these things and dispose of them when you are done.

Step 1 - Create a "base" Dockerfile

FROM postgres:16.2-bullseye

COPY data.sql /docker-entrypoint-initdb.d/data.sql

ENV POSTGRES_PASSWORD=password
ENV POSTGRES_USER=user
ENV PGDATA=/data

In the data.sql file put any SQL scripts you want Postgres to run on first run.

Step 2 - Build the Image

docker build -t app-data:raw .

Step 3 - Start and Run the Container

docker run -d -p 5432:5432 app-data:raw

Step 4 - Attach a shell and delete the init data.

In the container:

rm /docker-entrypoint-initdb.d/data.sql

Step 5 - Commit The Image

Exit the shell in the container, find the name given to your running instance, and do the following:

docker commit amazing_jones app-data:schema

Step 6 - Remove your container and start the new one

Step 7 - Repeat as necessary

Step 8 - Profit