Comment by fc417fc802

> you create a new empty process, then the parent calls syscalls to set up the new process ...

That does seem like a much better design to me. But I wonder if that was considered way back at the dawn of computing and rejected for good reason?

> I think this is technically possible on linux, but there isn't a readily available interface for it.

Yes there is, see `man clone`. POSIX and glibc are quite different from the kernel in this regard. AFAIK under linux there are just threads of execution that might or might not share various namespaces and memory mappings. That said, the kernel does place a few artificial restrictions on what combinations are allowed in order to (as I understand it) guard against the unintended exercise of entirely untested combinations that serve no known practical purpose.

The practical problem is that if you start doing as you please with the various namespaces and mappings you quickly become incompatible with glibc and by extension most likely the majority of the dynamic libraries available on your system.