I prefer to use Docker containers for running a PostgreSQL database.
Spin up the container, develop the app, then tear down the container. The Postgres database doesn’t clutter up my local system, and I can easily set it up on a different machine.
Using Docker Compose, I can configure the setup and commit it to source control.
In this blog post, I’ll show you how to get a database up and running with Docker and Docker Compose.
Postgres with Docker Compose⌗
Docker Compose allows you to write yaml files that are easy to read for humans and serve as instructions for Docker.
Go to the project folder of your application and create a new file:
version: '2.4' services: db: build: context: ./db dockerfile: Dockerfile ports: - 5432:5432 environment: - POSTGRES_USER=postgres - POSTGRES_PASSWORD=postgres volumes: - db-data:/var/lib/postgresql/data:delegated volumes: db-data:
We create a new service called
db (you can call it whatever you want).
The container runs on port 5432. Docker exposes that port on
You need to map the port inside the container to the host machine (your development computer).
Otherwise, your app won’t be able to connect to the Postgres database.
We also use some environment variables for the user and password.
What’s the deal with volumes?
Volumes are the preferred mechanism for persisting data generated by and used by Docker containers. 1
If you specify volumes in the
docker-compose.yml file, Compose preserves the volume:
docker-compose upruns, if it finds any containers from previous runs, it copies the volumes from the old container to the new container. This process ensures that any data you’ve created in volumes isn’t lost. 2
The empty top-level entry tells Compose that the utility should use the default driver for your machine.
Create a Dockerfile⌗
We told Compose that there will be a Dockerfile in the
Example folder structure:
. ├── db │ ├── init.sql │ └── Dockerfile ├── docker-compose.yml └── app
If you have a different folder structure, you need to adjust
context entry. At the moment, Docker looks for the
db directory in the root folder:
services: db: build: context: ./db
db directory and the
# pull official base image FROM postgres:12.2-alpine # run init.sql ADD init.sql /docker-entrypoint-initdb.d
(See Docker Hub for alternative images.)
Now we can use
init.sql to populate the database. We use a simple script that creates a new database called
CREATE DATABASE task_management;
I manage schema creation within my app in the language of my choice. For example, I use TypeORM (TypeScript) or SQLAlchemy (Python), depending on the web framework I’m using.
Now you can run the database. Inside the root directory, open the terminal and type:
docker-compose up -d
The command will start the container in detached mode (in the background).
If you want to use the command line to connect to the database:
docker-compose exec db psql -U postgres -d task_management
docker-compose exec: execute a command inside a running container
db: name of the service (see configuration in
psql: terminal command to run, see
-U postgres: user name is postgres
-d task_management: connect to the database called
You’ve seen how to create a simple configuration for Docker and Docker Compose that will create a Postgres container.
Now you can use the database for local development of your application.
- Database in a Docker container — how to start and what’s it about by Wojciech Krzywiec
- Docker Hub: Official postgres image