From UCL HEP PBT Wiki
Occasionally CERN will release patches or updates for Geant4. To update your version of Geant4 you will need root-access (using command “su”).
Before carrying out this process PLEASE make sure that you back-up any work that you have saved in the Geant4-build or Geant4-install directories.
1. Open a command terminal and log in as root user. Type “su” followed by your password when prompted
2. Change the present working directory to the Geant4-build directory using the command:
3. Type the command:
4. When this is done you will need to delete the folders Geant4-install and Geant4-build. To do this change your present working directory to the Desktop using the command
5. Now type the following command to delete the Geant4-build folder:
rm –rf Geant4-build
6. When this is finished type the following command to delete the Geant4-install folder:
rm –rf Geant4-install
7. Type the command exit to quit root-user mode
8. Now download the updated version of Geant4 and install it as directed by pp. 4-5 (using cmake –DCMAKE…..)