su: This applet requires root priviledges!

[yan seiner]

I am running on an embedded system.  I installed busybox and dropbear.

I can get root shell immediately without loging in at the console, which 
is fine.

The problem comes in when I try to su once I ssh in as an ordinary user.

I get:

~ $ su
su: This applet requires root priviledges!
~ $

How can I get root priveledges after I ssh in?

I don't mind having to log in at the console if that's required....  But 
I absolutely must have security at the network gates....

(These systems will be out in the open, connected via wi-fi, so I have 
to have login security, otherwise every high school kid will be running 
the equipment....)

--Yan