How to automatically start a service when running a docker container

A Docker container is an isolated environment created from a Docker image. It is a lightweight, standalone, executable package that includes everything needed to run an application.

In this article, we will see how to automatically start a service when running a docker container.

How to automatically start a service in docker?

First, we need to prepare a Dockerfile and need to define the service startup command in the Dockerfile. The Dockerfile is a text document that contains all the commands to assemble an image.

Following is the example Dockerfile

FROM ubuntu:latest

# Install necessary packages
RUN apt-get update && apt-get install -y your-service-package

# Copy service configuration file (if necessary)
COPY your-service.conf /etc/your-service.conf

# Expose the port your service listens on
EXPOSE 8080

# Define the command to start your service
CMD ["your-service", "start"]

1. In the above example, replace your-service-package, your-service.conf, and your-service with the actual names related to your service.

Build the docker image

Use the following command and Build the Docker image using the Dockerfile.

docker build -t your-service-image .

Run the docker container

Start the container from the image and the service will be automatically started.

docker run -d -p 8080:8080 your-service-image

In the above command, -d runs the container in the detached mode (i.e. in the background), and -p maps the container’s port to a port on the host.

Frequently asked questions

Can we start multiple services in one Docker container?

It’s possible, but not recommended. The best practice is to run one service per container for scalability and maintainability.

How do we ensure the service starts after a reboot or crash?

Docker automatically restarts containers if we use the --restart flag (e.g., --restart=always) when running a container.