When I try to run

pants run src/docker/hello_world:python

from this example, docker fails with

> [1/2] FROM <http://docker.io/library/python:3.8@sha256:e411647c253b75948394a343b13ff32b5674687df0c54187445d12ee9de2b106|docker.io/library/python:3.8@sha256:e411647c253b75948394a343b13ff32b5674687df0c54187445d12ee9de2b106>:
------
Dockerfile.python:4
--------------------
   2 |     # Licensed under the Apache License, Version 2.0 (see LICENSE).
   3 |     
   4 | >>> FROM python:3.8
   5 |     ENTRYPOINT ["/bin/main.pex"]
   6 |     COPY src.python.hello_world/main.pex /bin
--------------------
ERROR: failed to solve: failed to register layer: ApplyLayer exit status 1 stdout:  stderr: failed to Lchown "/etc" for UID 0, GID 0: lchown /etc: value too large for defined data type

Does anyone have an inkling on what this might be about?

Is this rootless docker?

It is indeed. Is that not the correct way to go about?

Well, Googling pretty quickly brings up not having proper

/etc/sub{g,u}id

maps