I have an NVIDIA graphics card (driver version 185.18.36), and wanted to use the proprietary drivers. However, every time I booted up, my resolution was set to a lower level than I wanted. I could re-set the resolution every session, using the NVIDIA control console, but I couldn't save the configuration with the control on the console, because I got the error message "Couldn't delete the file '/etc/X11/xorg.conf.backup'". I tried to delete this file manually, using Terminal and the "chown" command to obtain permissions for the delete, but the system would not allow me to delete the file.
Eventually, I found this advice on the webpage "
http://www.cyberciti.biz/faq/howto-linux-unix-delete-remove-file/":
"Usually, on most filesystems, deleting a file requires write permission on the parent directory (and execute permission, in order to enter the directory in the first place). (
Note that, confusingly for beginners, permissions on the file itself are irrelevant.)"
In order to allow the NVIDIA control program to re-set the display resolution permanently, I used this command on the Terminal program:
sudo chown username /etc/X11
You would use your own user name instead of "username". Problem solved.