You can see what updates are available by typing as sudo aptitude.

For example,

And if you don't want any package to update, then you can lock that package.

1. Open a terminal


2. Type sudo -s and hit enter



3. Enter your password for sudo

   
   
   

   echo libxfont1 hold | dpkg --set-selections
   
   



4. Replace libxfont1 with the package you want to pin


5. Now run sudo apt-get update and then sudo apt-get upgrade.

For more information, check how to pin packages.