Understanding Docker and LXC: Can Docker Run on LXC Containers?

Containers have revolutionized the way we deploy applications in a scalable and efficient manner. Docker and LXC are two prominent technologies in the container space, each with its unique features and advantages. This article delves into the relationship between Docker and LXC containers, focusing on whether Docker can run on LXC drivers and the transition to libcontainer.

Containerization Technologies: A Brief Overview

Before diving into the specifics, it's essential to understand the landscape of containerization technologies. Docker and LXC are both popular containerization solutions, each catering to different needs. Docker, developed by DotCloud and later acquired by Oracle, provides a high-level abstraction for deploying applications in isolated environments. On the other hand, LXC stands for Linux Control Groups and is a more low-level containerization tool that allows users to run isolated Linux systems within the same kernel. LXC has been around for many years and is highly customizable and flexible.

The Capacity of Docker to Utilize LXC Containers

One of the key questions surrounding Docker and LXC is whether Docker can run on LXC containers. While Docker is increasingly recognized as a more high-level and user-friendly tool, it is inherently capable of utilizing LXC drivers, especially in earlier versions. Starting from Docker version 0.9, Docker introduced libcontainer as its default driver, marking a significant shift in the way Docker handles containerization.

Docker's Evolution with libcontainer

The introduction of libcontainer represents a fundamental change in Docker's development approach. Libcontainer, a low-level, process-level container runtime, provides more control and flexibility to the Docker team. By making libcontainer the default driver, Docker simplified its internal processes, making the containerization experience more robust and reliable. However, Docker maintained the capability to switch to the LXC driver for those who still prefer the flexibility offered by LXC.

Setting Docker to Use LXC Driver

For users who wish to continue using the LXC driver, Docker provides a straightforward method to switch. The command to run Docker with the LXC driver is:

docker -d -e lxc

This command ensures that Docker will use the LXC driver instead of the default libcontainer driver. While this approach remains an option, it's important to note that using the LXC driver may limit some of the advanced features and improvements provided by libcontainer.

Advantages and Considerations of Choosing LXC over libcontainer

When deciding whether to use the LXC driver instead of the default libcontainer, it's crucial to weigh the advantages and potential drawbacks.

Advantages of Using LXC

Customization: LXC offers a high degree of customization, allowing users to fine-tune the container environment to meet specific requirements. Multiples of OS: LXC can run multiple Linux distributions within the same host, providing a versatile environment for testing. Flexibility: LXC's low-level nature grants users more control over the container's underlying operations.

Considerations with LXC

Complexity: LXC requires a deeper understanding of Linux system management and control groups, which might be overwhelming for beginners. Security: While LXC provides isolation, it may not offer the same level of security and isolation as more modern, high-level solutions like libcontainer. Support: Although LXC has a strong community and support base, the focus is shifting towards libcontainer in terms of continuous development and security updates.

Conclusion

In summary, while Docker has moved towards using libcontainer as its default driver, it still offers the flexibility to utilize the LXC driver. This choice depends on the specific needs of the user, such as the level of customization required and the familiarity with lower-level system management. As the technology continues to evolve, the risk and complexity of using LXC may decrease, but for now, it remains an alternative for those who prefer more control and flexibility in their container environment.