FreeBSD jails were long before Linux namespaces and cgroups and offered (I think) all the convenience of containers very early on. Namespaces and cgroups are a

FreeBSD jails were long before Linux namespaces and cgroups and offered (I think) all the convenience of containers very early on. Namespaces and cgroups are an evolution and improvement over jails, probably, because of other Linux things that existed in Linux. I don't know the whole history on this so I could be very wrong.