[adiabatichottub]

I'm not terrible familiar with Linux container systems, cgroups and all that, but I have been down the rabbit-hole with FreeBSD's jails, and I definitely wouldn't call them a capabilities system. You can lock down the environment quite a bit, and limit or even virtualize the network stack, but you can't say, "Here process, have your standard IO streams and nothing more. Go forth and compute." The process isn't blind to it's environment. You're still in the same basic UNIX user security model. It's really somewhere between chroot and full virtualization.

[harporoeder]

A default container seccomp profile will let you do quite a few things but you can use a different profile some json and limit to just a few system calls if you want such as doing IO on open FDs without the ability to open them. I think the runtime opens the FDs before the child process starts and are inherited.