Apptainer vs Buildah

Apptainer is a free container platform for creating and running portable, reproducible workloads, with a focus on shared systems and high-performance computing. It packages containers as immutable, single-file Singularity Image Format (SIF) images designed for transport and sharing. By default, users retain the same privileges inside and outside containers. Images can be signed and verified with PGP keys, PEM keys or X.509 certificates, and encrypted containers can run without writing decrypted contents to disk. Apptainer imports containers from OCI registries and aims to support most Docker Hub containers without changes. It can expose host resources such as GPUs, high-speed networks and parallel filesystems, and supports NVIDIA CUDA, AMD ROCm, Intel Gaudi and OCI Container Device Interface accelerators. Running Apptainer requires Linux; Windows and macOS need a Linux virtual machine, with Windows also listed via WSL2. Root access is unnecessary when user namespaces are available. Full functionality requires kernel support for FUSE and unprivileged user namespaces. Community support includes Slack, Google Groups and GitHub, with commercial services through CIQ.

Buildah is a free command-line tool for building OCI container images on Linux. It can create images from working containers, Dockerfiles, or Containerfiles, and can also build through commands and scripts without a build file. Output can use OCI format or the traditional upstream Docker image format. Builds can run without root privileges, and Buildah follows a fork-exec model rather than running as a daemon. Its commands create, mount, unmount, delete, and rename working containers, as well as create or delete images; users can also pull images from a specified location and push local images elsewhere. Buildah is based on a Go API that other tools can vendor, and Podman uses it for Dockerfile builds while remaining independently installable. Buildah requires a kernel with OverlayFS or fuse-overlayfs support; RHEL or CentOS requires version 7.4 or later. Installation guidance warns that short image names can be spoofed and recommends fully qualified names from trusted registries or pulling by digest. The project points users to tutorials, releases, and a mailing list for questions.