To prevent anyone from making changes to Ubuntu, you only need to disable "paste", because even though they can cut and copy, they will not be able to paste it any place. So in effect those two functions are also disabled. To do this enter the /Home folder and right clicking the folder/s inside of it and select Properties. On the Permissions tab set the Owner's file access to "Access files". Then set the other two Folder access boxes to "List files only." Next click the "Apply Permissions to Enclosed Files" button and click close. Nothing on your system can be changed now. I don't know if this will prevent then from copying stuff onto their own computers or not.
Last edited by Tinkster; 08-29-2011 at 06:51 PM.