Running 𝒔𝒚𝒔𝒕𝒆𝒎𝒄𝒕𝒍 Inside a Docker Container: A Practical Guide

3 min readOct 31, 2024

Running systemd services inside Docker containers can be challenging, but it’s sometimes necessary for managing services like Apache within containerized environments. This guide will walk you through the process of enabling systemctl functionality in a Docker container.

Step 1: Create a Dockerfile

First, create a directory for your Dockerfile:

mkdir docker-systemd
cd docker-systemd
nano Dockerfile

Add the following content to your Dockerfile:

FROM centos:7

# Install systemd
RUN yum -y update && yum -y install systemd

# Remove unnecessary systemd services
RUN (cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i == syste>
    rm -f /lib/systemd/system/multi-user.target.wants/*; \
    rm -f /etc/systemd/system/*.wants/*; \
    rm -f /lib/systemd/system/local-fs.target.wants/*; \
    rm -f /lib/systemd/system/sockets.target.wants/*udev*; \
    rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
    rm -f /lib/systemd/system/basic.target.wants/*; \
    rm -f /lib/systemd/system/anaconda.target.wants/*;

# Install a service (e.g., nginx)
RUN yum -y install nginx

VOLUME [ "/sys/fs/cgroup" ]

This Dockerfile uses a CentOS base image with systemd support and sets it to run in the foreground.

Step 2: Build the Docker Image

Build your Docker image:

sudo docker run -d --name systemd-container --privileged -v /sys/fs/cgroup:/sys/fs/cgroup:ro centos:7 /usr/sbin/init
docker build -t centos .
sudo docker exec -it centos systemctl status

Step 3: Run the Container

To run the container with systemd support, use the following command:

docker run --privileged \
  -v /sys/fs/cgroup:/sys/fs/cgroup:ro \
  -v /run/systemd/system:/run/systemd/system \
  -v /var/run/dbus/system_bus_socket:/var/run/dbus/system_bus_socket \
  -it centos /sbin/init

This command:

Runs the container in privileged mode
Mounts necessary volumes for systemd functionality
Starts the systemd init process

Step 4: Access the Container

In a new terminal window, access your running container:

docker exec -it <container_id> /bin/bash

Replace <container_id> with your actual container ID.

Step 5: Use systemctl

Now you can use systemctl commands inside the container:

systemctl status docker
systemctl start docker

Conclusion

By following these steps, you’ve successfully enabled systemctl functionality within a Docker container. Remember that running systemd in containers is not a standard practice and should be used cautiously, as it can impact container isolation and portability. For most use cases, it’s preferable to design containers that run a single process directly, without relying on an init system.

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