HPSF Conference 2025: Full Schedule

May 5-8, 2025
Chicago, IL
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IMPORTANT NOTE: Timing of sessions and room locations are subject to change.

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9:00am CDT

Introduction to Containers and Charliecloud - Reid Priedhorsky, Los Alamos National Laboratory

Wednesday May 7, 2025 9:00am - 9:40am CDT

Illinois River

Charliecloud is a lightweight, fully unprivileged, open source container implementation for HPC applications. It can handle the entire container workflow, including building images, pushing/pulling to registries, and dealing with accelerators like GPUs. We take a unique approach to containerization while remaining compatible with the broader container ecosystem where it matters.

Notable distinctions include: fully unprivileged end-to-end workflow, small code base with minimal dependencies, delegation of all security boundaries, layer-free build cache, zero-consistency root emulation based on seccomp, and a spirit of openness and public service.

This talk will motivate containers for HPC applications, then explain Charliecloud’s design philosophy and how we address these needs. We’ll discuss Charliecloud’s “weirdness” when compared to other implementations (i.e., its design philosophy and key distinctions), provide a brief overview of the code’s structure, and summarize recent and upcoming changes of interest.

LA-UR-25-22140

Speakers

Reid Priedhorsky

Scientist, Los Alamos National Laboratory

I am a staff scientist at Los Alamos National Laboratory. Prior to Los Alamos, I was a research staff member at IBM Research. I hold a Ph.D. in computer science from the University of Minnesota and a B.A., also in computer science, from Macalester College.My work focuses on large-scale... Read More →

Wednesday May 7, 2025 9:00am - 9:40am CDT
Illinois River

Charliecloud

9:40am CDT

Charliecloud Workshop: Key Workflow Operation - Pull - Megan Phinney, Los Alamos National Laboratory

Wednesday May 7, 2025 9:40am - 10:00am CDT

Illinois River

This workshop will provide participants with background and hands-on experience to use basic Charliecloud containers for HPC applications. Participants will build toy containers and a real HPC application, and then run them in parallel on a supercomputer. This will be a highly interactive workshop with lots of Q&A.

This section will walk through the key workflow operation pull.

LA-UR-25-22140

Speakers

Megan Phinney

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 9:40am - 10:00am CDT
Illinois River

Charliecloud

10:00am CDT

Charliecloud Workshop: Containers Are Not Special Alpine via Tarball - Megan Phinney, Los Alamos National Laboratory

Wednesday May 7, 2025 10:00am - 10:20am CDT

Illinois River

This workshop will provide participants with background and hands-on experience to use basic Charliecloud containers for HPC applications. Participants will build toy containers and a real HPC application, and then run them in parallel on a supercomputer. This will be a highly interactive workshop with lots of Q&A.

This section will explain that containers are not special by running an Alpine container via tarball.

LA-UR-25-22140

Speakers

Megan Phinney

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 10:00am - 10:20am CDT
Illinois River

Charliecloud

10:45am CDT

Charliecloud Workshop: Key Workflow Operation - Build from Dockerfile - Megan Phinney, Los Alamos National Laboratory

Wednesday May 7, 2025 10:45am - 11:05am CDT

Illinois River

Speakers

Megan Phinney

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 10:45am - 11:05am CDT
Illinois River

Charliecloud

11:05am CDT

Charliecloud Workshop: Key Workflow Operation - Push - Megan Phinney, Los Alamos National Laboratory

Wednesday May 7, 2025 11:05am - 11:25am CDT

Illinois River

Speakers

Megan Phinney

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 11:05am - 11:25am CDT
Illinois River

Charliecloud

11:25am CDT

Charliecloud Workshop: MPI Hello World - Megan Phinney, Los Alamos National Laboratory

Wednesday May 7, 2025 11:25am - 11:45am CDT

Illinois River

This workshop will provide participants with background and hands-on experience to use basic Charliecloud containers for HPC applications. Participants will build toy containers and a real HPC application, and then run them in parallel on a supercomputer. This will be a highly interactive workshop with lots of Q&A.

This section will include a multi-node MPI hello world example.

LA-UR-25-22140

Speakers

Megan Phinney

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 11:25am - 11:45am CDT
Illinois River

Charliecloud

11:45am CDT

Charliecloud Workshop: Wrap-up - Megan Phinney, Los Alamos National Laboratory

Wednesday May 7, 2025 11:45am - 12:05pm CDT

Illinois River

This workshop will provide participants with background and hands-on experience to use basic Charliecloud containers for HPC applications. Participants will build toy containers and a real HPC application, and then run them in parallel on a supercomputer. This will be a highly interactive workshop with lots of Q&A.

This section will wrap-up the workshop with final Q&A.

LA-UR-25-22140

Speakers

Megan Phinney

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 11:45am - 12:05pm CDT
Illinois River

Charliecloud

1:35pm CDT

Key Charliecloud Innovation - Build Cache - Reid Priedhorsky, Los Alamos National Laboratory

Wednesday May 7, 2025 1:35pm - 1:55pm CDT

Illinois River

Container images are built by interpreting instructions in a machine-readable recipe, typically a Dockerfile, which is often faster with a build cache that stores instruction results for re-use. The standard approach (used e.g. by Docker and Podman) is a many-layered union filesystem, encoding differences between layers as tar archives.

This talk describes a new approach, as implemented in Charliecloud: store changing images in a Git repository. Our experiments show this performs similarly to layered caches on both build time and disk usage, with a considerable advantage for many-instruction recipes. Our approach also has structural advantages: better diff format, lower cache overhead, and better file de-duplication. These results show that a Git-based cache for layer-free container implementations is not only possible but may outperform the layered approach on important dimensions.

LA-UR-25-22140

Speakers

Reid Priedhorsky

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 1:35pm - 1:55pm CDT
Illinois River

Charliecloud

1:55pm CDT

Key Charliecloud Innovation - SIF - Krishna Chilleri, Los Alamos National Laboratory

Wednesday May 7, 2025 1:55pm - 2:15pm CDT

Illinois River

The Singularity Image Format (SIF) is a compressed read-only SquashFS filesystem that includes everything needed to run a containerized application. Leveraging its SquashFS-based architecture, Charliecloud has integrated support for the reading and execution of this image format. This talk will provide details about how the ch-run functionality identifies SIF files, analyzes the file header structure, and retrieves the SquashFS partition offset needed for container image execution.

Additionally, the talk is designed for anyone looking to gain a clearer understanding of SIF, especially if you find the upstream documentation challenging to navigate.

LA-UR-25-22166

Speakers

Krishna Chilleri

Student, Los Alamos National Laboratory

Wednesday May 7, 2025 1:55pm - 2:15pm CDT
Illinois River

Charliecloud

2:15pm CDT

Key Charliecloud Innovation - squashfs - Megan Phinney, Los Alamos National Laboratory

Wednesday May 7, 2025 2:15pm - 2:35pm CDT

Illinois River

The typical filesystem image formats for Charliecloud are SquashFS and tar archives. SquashFS is a compressed, read-only filesystem that unprivileged users can mount in user space with SquashFUSE; it is the preferred image format due to its various efficiencies. The previous SquashFS workflow was non-ideal due to user complexity and difficulties with HPC job schedulers.

We have designed a workflow that requires us to link SquashFUSE to Charliecloud to enable the new mount/unmount procedure of only needing a single user command. Also, an additional persistent process is needed to service the FUSE requests called the FUSE loop: once the containerized application process finishes, it unmounts the SquashFS and ends the FUSE loop. Our SquashFS workflow is currently in production with it being more user friendly, cleans up after itself and is more compatible with HPC job schedulers. We were able to reduce user commands from 3 to 1, increase reliability and decrease mount/unmount time by more than 50%.

LA-UR-25-22140

Speakers

Megan Phinney

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 2:15pm - 2:35pm CDT
Illinois River

Charliecloud

2:35pm CDT

Key Charliecloud Innovation - seccomp - Reid Priedhorsky, Los Alamos National Laboratory

Wednesday May 7, 2025 2:35pm - 2:55pm CDT

Illinois River

Do Linux distribution package managers need the privileged operations they request to actually happen? Apparently not, at least when building container images for HPC applications. Charliecloud uses this observation to implement a root emulation mode using a Linux seccomp filter that intercepts some privileged system calls, does nothing, and returns success to the calling program. This approach provides no consistency whatsoever but is sufficient to build a wide selection of Dockerfiles, including some that Docker itself cannot build, simplifying fully-unprivileged workflows needed for HPC application containers. This talk will detail the approach along its advantages and disadvantages.

LA-UR-25-22140

Speakers

Reid Priedhorsky

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 2:35pm - 2:55pm CDT
Illinois River

Charliecloud

2:55pm CDT

Key Charliecloud Innovation - CDI - Reid Priedhorsky, Los Alamos National Laboratory

Wednesday May 7, 2025 2:55pm - 3:15pm CDT

Illinois River

An ongoing challenge for HPC containers is how to make host resources such as GPU devices and proprietary interconnects performantly available inside a container. In Charliecloud, the key requirement is placing shared libraries (.so files) into the container and then running ldconfig(8) to update its cache. (Other implementations also have to deal with device files and their associated permissions and symlinks, but because Charliecloud bind-mounts host /dev into the container, this is not needed).

Charliecloud has done this for some time using ch-fromhost(1), which is a large, reverse-engineered shell script that copies the needed files into a writeable image. It is difficult to maintain, does not support SquashFS or other write-only images, and adds a workflow step.

Other implementations typically use “OCI hooks”, which are arbitrary vendor-provided or custom programs run at various phases during container setup. These also present maintainability / bit-rot problems, can be opaque, and because their interface is solely “do it for me”, any invalid assumptions that hooks make can be difficult or impossible to work around.

A different approach is the emerging Container Device Interface (CDI) standard, with contributors from nVidia, Intel, Los Alamos, and others. This gives prescriptive JSON/YAML descriptions of what is needed. Charliecloud has implemented CDI in its runtime ch-run(1), bind-mounting requested files and using an unprivileged tmpfs overlay (available since Linux 5.11 in February 2021) to avoid modifying the image. This is a considerably simpler and more maintainable way to make host resources available inside a container.

This talk will provide an overview of CDI, adaptations of the standard to our fully unprivileged workflow, and our C implementation. We will also demonstrate the functionality for nVidia GPUs and HPC/Cray Slingshot interconnect.

LA-UR-25-22140

Speakers

Reid Priedhorsky

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 2:55pm - 3:15pm CDT
Illinois River

Charliecloud

3:40pm CDT

Charliecloud Office Hours - Reid Priedhorsky, Los Alamos National Laboratory

Wednesday May 7, 2025 3:40pm - 5:00pm CDT

Illinois River

Members of the Charliecloud team will be available for office hours to listen to feedback/suggestions, answer questions, and/or help debug issues.

LA-UR-25-22140

Speakers

Reid Priedhorsky

Scientist, Los Alamos National Laboratory

Wednesday May 7, 2025 3:40pm - 5:00pm CDT
Illinois River

Charliecloud