cosimo321@ubuntu:~$ su
Password: 
root@ubuntu:/home/cosimo321# aptitude hold xserver-xorg-video-ati
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Reading extended state information      
Initializing package states... Done
Building tag database... Done      
The following packages have been kept back:
  xserver-xorg-video-ati 
0 packages upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
Need to get 0B of archives. After unpacking 0B will be used.
Writing extended state information... Done
root@ubuntu:/home/cosimo321# apt-get dist-upgrde
E: Invalid operation dist-upgrde
root@ubuntu:/home/cosimo321# apt-get dist-upgrade
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
  xserver-xorg-video-ati
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 379kB of archives.
After unpacking 45.1kB of additional disk space will be used.
Do you want to continue [Y/n]? 
root@ubuntu:/home/cosimo321#