Re: Questions about Jail



Fbsd8 <fbsd8@xxxxxxxxxxxxxxx> wrote:

In most cases your jail environment will function ok as long as
its the same base release level. Example, host=8.0 jail1=8.1 and
jail2=8.2

IIUC, a better example would be host=8.2, jail1=8.1 and jail2=8.0.
A point release is not supposed to make any incompatible changes to
the kernel ABI, but it might add new interfaces not present in the
older kernel.

But host=8.2 and jail1=9.0 will have unknown reliability.

I would say it is only an accident if (jail major > kernel major)
works, because the KABI will likely have changed between N.x and
(N+1).x. However, host=9.0, jail1=8.x should work if the host
kernel includes the COMPAT_FREEBSD8 option.

Technically there is no checks stopping someone from doing this
and from the outside all will look correct, but it will fail and
you may lose both the host and jail.

You may indeed lose the jail, but if _anything_ done in the jail is
able to corrupt the host there is by definition a bug in the host's
jail support.
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