Setup OpenRC in Alpine Container

Date: [17th Dec 2024]
Categories: [Tech]
Tags: [Linux], [Container]

Alpine Linux is a lightweight Linux distribution often used in containerized environments. One of the key difference in full and containerized Alpine Linux installation is openrc, a dependency-based init system. While OpenRC exists by default in clean Alpine install, it is usually absent in a container image.

In this blog post, we'll walk through the steps to set up openrc in an Alpine Linux container and demonstrate how to start an Nginx server using openrc.

Big thanks to Holy semicolon from StackOverflow for this answer: How to start Nginx server within alpine image using rc-service command

Step-by-Step Guide

1. Spawn the Container

First, let's spawn an Alpine Linux container. Open your terminal and run the following command:

docker run -it alpine

This command will pull the Alpine Linux image if you don't have it locally and start an interactive shell session within the container.

2. Update and Upgrade Packages

It's always a good practice to ensure your package list is up-to-date and all installed packages are upgraded to their latest versions. Run the following commands inside the container:

apk update && apk upgrade

3. Install `openrc`

Next, install openrc using the Alpine package manager apk:

apk add openrc

4. Initialize the System with `openrc`

To initialize the system with openrc, simply run the openrc command in the shell:

openrc

This command sets up the necessary directories and files for openrc to function correctly.

5. Create the Missing `softlevel` File

openrc does not create the softlevel file automatically. This file is necessary for openrc to track the current runlevel. Create the file manually with the following command:

touch /run/openrc/softlevel

6. Start the Nginx Server

Now that openrc is set up, you can manage services using the rc-service command. Let's demonstrate this by starting an Nginx server.

First, check the status of the Nginx service:

rc-service nginx status

Since Nginx is not installed by default, you'll need to install it first:

apk add nginx

After installing Nginx, start the service:

rc-service nginx start

Finally, check the status again to ensure Nginx is running:

rc-service nginx status

You should see output indicating that the Nginx service is running.

Conclusion

Setting up openrc in an Alpine Linux container is a straightforward process that involves updating packages, installing openrc, initializing the system, and creating a necessary file. Once openrc is set up, you can easily manage services like Nginx using the rc-service command.

This setup is particularly useful in containerized environments where you need a lightweight and efficient way to manage services. Happy containerizing!