Apptainer vs firecracker-containerd

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.

firecracker-containerd lets containerd manage containers as Firecracker microVMs, adding isolation through the KVM hypervisor. Potential uses include sandboxing untrusted third-party containers and bin-packing different workloads on multi-tenant hosts. It uses OCI image format where possible. The project includes a control plugin and API, an out-of-process shim runtime, an agent inside the microVM, and a root filesystem image builder. That agent invokes runC through containerd-shim-runc-v1 to create Linux containers inside the microVM. Networking supports pre-created tap devices and tap devices created by CNI plugins such as bridge, ptp, host-local, firewall, and tc-redirect-tap. The software is free under Apache 2.0. Hosts require Linux 4.14 or later, Intel x86_64, and KVM; AMD and Arm are not supported. Building requires git, gcc, Docker CE, and Go 1.23 or later. The guide describes the project as very early, and multi-tenant use is at the user’s own risk.