[rsync]

"Yes, everyone refers to jails, but I think most people would agree that jails weren't really containers. They didn't provide true isolation for a set of applications. I guess you could argue they were the original prototype for them though."

The first VPS provider (JohnCompanies, 2001) was based entirely on jail and it absolutely provided (even then) true isolation for a set of applications.

Every customer had their own unix root and their own rc.conf configured their own system and everyone ran their own sendmail/named/httpd/etc.

It is absolutely correct to refer to jails in this way, and that is why you see everyone doing it.

[binarycrusader]

If you're talking about chroot jails, no, it was possible to "escape" jails they did not provide true isolation.

If you're talking about some other jail, possibly, but my understanding is they didn't actually provide true isolation. Certainly not a kernel-level of abstraction.