Postgres Containers with Docker

In this guide i want to explain how can we set up a simple PostgreSQL container using two methods: directly through the Docker CLI and using a Docker Compose file.

Additionally, we’ll cover some basic commands for managing your containers.

Method 1: Creating a Container Using the Docker CLI

You can create a PostgreSQL container directly from the command line using the following command:

$ docker run --name postgres-container -e POSTGRES_PASSWORD=yourpassword -e POSTGRES_USER=postgres -d postgres

Explanation of the Command

1. docker run The fundamental command to create and start containers.
2. --name postgres-container Assigns a specific name to the container.
3. -e POSTGRES_PASSWORD=yourpassword Sets the PostgreSQL password using an environment variable.
4. -e POSTGRES_USER=postgres Specifies the PostgreSQL user.
5. -d Runs the container in detached mode (in the background).
6. postgres Specifies the image name to be used for creating the container.

Key Notes:

• Flags: Options used to define container characteristics. For instance, -e sets environment variables, while --name specifies the container name.

Method 2: Using a Docker Compose File

For better organization and visibility, you can use a Docker Compose file. Create a file named docker-compose.yml with the following content:

services:
postgres:
  image: postgres:15
  container_name: ${POSTGRES_CONTAINER_NAME}
  environment:
    POSTGRES_DB: keycloak
    POSTGRES_USER: admin
    POSTGRES_PASSWORD: admin
  volumes:
    - postgres_data:/var/lib/postgresql/data
  ports:
    - "${POSTGRES_PORT:-5432}:5432"
  networks:
    - keycloak_network

Explanation of docker-compose.yml

1. services Lists the services to be managed by Docker Compose. In this case, only postgres is defined.
2. image Specifies the Docker image to use (e.g., postgres:15).
3. container_name Defines the name of the container.
4. environment Sets environment variables such as database name, user, and password.
5. volumes Maps container directories to local directories for persistent storage.
6. ports Maps container ports to local ports. The format is local_port : container:port.
7. networks Specifies the network configuration.

If you are using a docker-compose.yml file you will need tthe command below to execute it, make sure you are in the same location as your docker-compose file and type:

$ docker compose up

This will start your services right on. Similar to it we can take our containers down with:

$ docker compose down

Managing Docker Containers

Here are some essential commands for managing your containers:

Accessing a Container

$ docker exec -it <container_name_or_id> sh

Viewing Logs of a Container

$ docker logs <container_name_or_id>

Stopping a Container

$ docker stop <container_name_or_id>

Starting a Container

$ docker start <container_name_or_id>

Removing a Container

$ docker rm <container_name_or_id>

By using these methods and commands, you can easily set up and manage PostgreSQL containers.