You Asked, We Answered: FAQs About Apptainer

As containers gain popularity in High Performance Computing (HPC) environments, Apptainer (formerly known as Singularity) has become the leading container system for HPC. For those seeking more information about Apptainer and the benefits of containerization, we’ve curated a list of Frequently Asked Questions (FAQs), designed for both beginners and seasoned experts in the field. This resource, which can be found at the bottom of the Apptainer page, breaks down the basics and deep-dives into the details, answering: 

• What is a container?

• What is the difference between containers and virtual machines (VMs)?

• I’ve heard that Apptainer was built for HPC. What does that mean?

• Why “reinvent the wheel” with a new container platform for HPC?

• What is the relationship between Apptainer and Singularity?

• What is the difference between OCI (Docker) images and SIF (Apptainer) images?

• Does orchestration (like Kubernetes or Docker Swarm) work with Apptainer?

• I’ve heard the phrase “Integration over Isolation.” What does it mean? 

• I just downloaded a new container and I can’t find the software inside of it. How do I find the program I want to run?

• Can Apptainer run nested containers? (Or other container runtimes like Podman?)

• How can I submit a containerized job through a workload manager like Slurm or PBS? 

• How can I run my MPI-enabled programs in Apptainer? 

• How do I access ports for running services in my container?

• How do I view graphics produced by containerized programs? 

• What is the best strategy for importing libraries and executables from the host or from other containers into my container?

• How do I containerize applications transparently on behalf of users I support?

If you have more questions, you can find freely available support resources by reaching out to the Slack community, the Apptainer project’s Google Groups, or the Apptainer GitHub repo. CIQ also offers expert support and services.

Still want to learn more? Check out these additional Apptainer resources: 

• Container Education Series: Your Ultimate Guide to Apptainer

• Container Education Series: Apptainer MPI Benchmarking

• Containerization, Cloud, Collaboration: Cutting-Edge Approaches with Altair and CIQ

• Navigating Container Security - Apptainer vs. Rootless Podman Unveiled

• Apptainer: Deep Dive, Use Cases, and Examples

• Apptainer Solution Brief