[quadruplebond]

What do you mean bare metal? Because all of the big DOE computers are running Linux. Users will probably use hardware specific libraries (like CUDA/ROCm) and occasionally write some hardware specific asm, but none of the big computers are running without a POSIX OS.

[cozzyd]

I think they mean not in a VM, and instead using some job manager like slurm or condor. Typically users wouldn't have superuser privligles precluding the use of thigns like docker, which is why Singularity exists.