Calling "VM-like" is not helpful because containers have also been called that, it also doesn't explain anything. Is it running a separate kernal image? Does it do hypercalls to the host kernel? If not then I wouldn't call it VM-like.
The low-level details and fiddly knobs matter, not how it looks like from userspace when all is done.
Based on the jail(8) manpage I get the impression that jails are more like all the namespace and cgroup things rolled into a single entity. Which I guess makes it more difficult to use them incorrectly. But it also prevents other uses such as the one that jmillikin has in mind.
The low-level details and fiddly knobs matter, not how it looks like from userspace when all is done.
Based on the jail(8) manpage I get the impression that jails are more like all the namespace and cgroup things rolled into a single entity. Which I guess makes it more difficult to use them incorrectly. But it also prevents other uses such as the one that jmillikin has in mind.