Q: How to turn on Num Lock on GNOME startup?

1. Read General Notes
2. Read How to add extra repositories?

3. sudo apt-get install numlockx
   sudo cp /etc/X11/gdm/Init/Default /etc/X11/gdm/Init/Default_backup
   sudo gedit /etc/X11/gdm/Init/Default

4. Find this line

   ...
   exit 0

5. Add the following lines above it

   if [ -x /usr/bin/numlockx ]; then
     /usr/bin/numlockx on
   fi

6. Save the edited file (sample)
7. Read How to restart GNOME without rebooting computer?