Zero-consistency root emulation for unprivileged container image build

TL;DR

This paper introduces a seccomp-based root emulation mode that intercepts privileged system calls during container image building, enabling fully-unprivileged workflows for HPC applications without requiring privileged operations.

Contribution

The authors present a novel seccomp filter approach that emulates root privileges during container build processes, simplifying unprivileged container workflows for HPC applications.

Findings

Successfully builds Dockerfiles without privileged operations

Simplifies container workflows for HPC applications

No consistency guarantees but sufficient for practical use

Abstract

Do Linux distribution package managers need the privileged operations they request to actually happen? Apparently not, at least for building container images for HPC applications. We use 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 appears sufficient to build all Dockerfiles we examined, simplifying fully-unprivileged workflows needed for HPC application containers.