Unix has process groups. Unix has access control (ie. memory protection, FS access protection, FS root aka chroot). Containers are process groups with access

Unix has process groups. Unix has access control (ie. memory protection, FS access protection, FS root aka chroot). Containers are process groups with access control. The actual entity has a different name pretty much everywhere, eg. Solaris Zone, Linux namespace and Linux cgroups. Usually the OS throws in a wider bunch of stuff that is only loosely related to access control in the classic sense, eg. CPU and memory limiting, I/O rate limiting and such (so rusage access control, in a sense).