> А что урезано в линуп.совом su?

man su фря
> In particular, by default
>     only users in the “wheel” group can switch to UID 0 (“root”).

https://web.archive.org/web/20131210155635/http://www.gnu.or...
> However, GNU su does not check if the user is a member of the wheel group; see below.
> 23.6.1 Why GNU su does not support the ‘wheel’ group
> (This section is by Richard Stallman.)
> Sometimes a few of the users try to hold total power over all the rest.

...
> However, occasionally the rulers do tell someone. Under the usual su mechanism, once someone learns the root password who sympathizes with the ordinary users, he or she can tell the rest. The “wheel group” feature would make this impossible, and thus cement the power of the rulers.

В общем, из-за каких-то фанати^W идеологических соображений (была) вырезана поддержка su -> только для группы wheel