> Containers are single-process things - they're not running syslog or cron or any of that overhead, for example.

You're either being entirely too prescriptive or interchanging containers and Docker freely when they are not equivalent, though one is a particular implementation of the other.

People have been running containers that emulate a full system for quite a while (see FreeBSD jails, illumos/Solaris zones, Linux OpenVZ, LXC, etc.).