http://www.cyberciti.biz/faq/freebsd-mount_nullf-usrports-inside-jail/

as host root
--
D=/jail/www
# mkdir -p $D/usr/ports
# mount_nullfs /usr/ports $D/usr/ports
## you may umount ports after you finished jailed port install

as jailed root
--
/usr/ports/ports-mgmt/portupgrade
jj# rehash
jj# pkgdb -Ff
portupgrade -f p5\* 
portupgrade -fr perl

/usr/ports/net/dropbox-api-command

Now login to jail called www (jail id # 10):
Try to install apache22:

~/bin/sync_dropbox
into crontab