title: Mounting proc in non-privileged namespace sandbox
body: <p>I'm trying to make a sandboxed environment using Linux namespaces. I've found a neat example at <a href="https://github.com/swetland/mkbox" rel="nofollow noreferrer">https://github.com/swetland/mkbox</a> that roughly does what I want, but I'd like a credible /proc to appear inside the sandbox. How can I do that?</p>
  
  <p>I tried bind mounting the proc FS on "proc", but that fails with EINVAL. When I try to mount "proc" normally, it yields EPERM.</p>
  
  <p>ideas?</p>