About Containers
Lightweight, isolated environments that contain all the tools needed to run applications. They have become essential in the field of computing due to their flexibility and efficiency.
What is a container?
- A container is a self-contained execution unit that encapsulates an application, as well as external libraries and other dependencies necessary for its execution.
- It provides an isolated environment, ensuring that embedded applications function identically regardless of the host on which they are deployed.
- It is a lightweight object, as it only includes what is necessary for its execution. It does not burden itself with a complete operating system, and the container communicates directly with the host machine’s kernel to access hardware resources.
What are the benefits?
- Portability: containers encapsulate everything an application needs to run, ensuring that its execution is identical regardless of the operating system. This characteristic facilitates portability between development, testing, and production environments.
- Isolation: each container is isolated from others and from the host, avoiding conflicts between dependencies and ensuring the security of the application.
- Reproducibility: by essence, a container is a self-sufficient and immutable object. It runs identically on the software environment of a desktop machine or a computing grid, and always operates the same over time, regardless of updates or changes in the host’s library versions.
- Scalability and reversibility: the lightweight and easy deployment of containers simplifies the implementation of updates and patches by creating new containers. At the same time, it is just as easy to revert to a previous version in case of issues, ensuring stability in the deployment and integration process.
- Resource management: containers share the host’s operating system kernel, making them lighter than virtual machines that require more system resources.
In summary, containers offer a powerful solution for application deployment, improving the flexibility, reproducibility, portability, and efficiency of development and deployment processes.
In practice, you can choose the technical solution you want to use locally on your machine. For the DIAMOND project, we recommend using both Apptainer and Guix. On the other hand, for clusters or data centres, the solution depends on what’s available. Almost half of the French mesocentres and national data centres have a container system available as a standard command (enabling the use of containers). It should be noted, however, that the other half offers the possibility of loading a container system via the module load command (and thus of using containers). On the other hand, the use of Guix is limited to less than $30\%$ of all French computing centres. It’s worth noting that the MESONET project, which aims to pool HPC computing resources across the country, has deployed a solution for using containers on its prototyping cluster. Although not all of the project’s clusters are available yet, it is highly likely that they will all feature a container system.