podman/docs/source/markdown/options/userns.image.md

####> This option file is used in: ####> podman build, farm build ####> If file is edited, make sure the changes ####> are applicable to all of those.

--userns=how

Sets the configuration for user namespaces when handling RUN instructions. The configured value can be "" (the empty string) or "container" to indicate that a new user namespace is created, it can be "host" to indicate that the user namespace in which podman itself is being run is reused, or it can be the path to a user namespace which is already in use by another process.