[Samba] Exist any method to restrict the Admin Domain to access the root resources?

[root]

Hi,

I try the username map in the smb.conf, and put the next line:
root = donadmin

How restrict this Admin Domain (donadmin) to access the resources of the root:

[root at bch:/]# /usr/local/samba/bin/smbclient //192.168.0.1/root -U donadmin%any
smb: \> mkdir testing
smb: \> exit

[root at bch:/]# ls -ld testing/
drwxr-xr-x   2 root     other        512 Jan 13 13:14 testing/

[root at bch:/]# rmdir testing/