яйцо в утке, утка в зайце...

[netch80]

Author: jamie
Date: Wed May 27 14:11:23 2009
New Revision: 192895
URL: http://svn.freebsd.org/changeset/base/192895

Log:
  Add hierarchical jails.  A jail may further virtualize its environment
  by creating a child jail, which is visible to that jail and to any
  parent jails.  Child jails may be restricted more than their parents,
  but never less.  Jail names reflect this hierarchy, being MIB-style
  dot-separated strings.

Не знаю, насколько полезно, но выглядит очень круто:)