Zero-consistency root emulation for unprivileged container image build

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.