jail.8: Add creating a jail from package base

MFC after:		immediately for inclusion in 15.0R
Reported by:		ivy
Differential Revision:	https://reviews.freebsd.org/D53745

usr.sbin/jail/jail.8

@@ -26,7 +26,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd November 6, 2025
+.Dd November 13, 2025
 .Dt JAIL 8
 .Os
 .Sh NAME
@@ -1147,6 +1147,13 @@ D=/here/is/the/jail
 mkdir -p $D
 tar -xf /usr/freebsd-dist/base.txz -C $D --unlink
 .Ed
+.Ss Setting up a Jail Directory Tree from System Packages
+To set up a jail directory tree containing an selectable
+.Fx
+distribution with the packages tech preview,
+the following command can be used:
+.Pp
+.Dl bsdinstall jail /here/is/the/jail
 .Pp
 In many cases these examples would put far more in the jail than needed.
 In the other extreme case a jail might contain only one file: