$ sudo apt-get update
$ sudo apt-get install gconf-service-backend 

gconf-service-backend is installed in your system.

Make ensure the gconf-service-backend package were installed using the commands given below,

$ sudo dpkg-query -l | grep gconf-service-backend *

You will get with gconf-service-backend package name, version, architecture and description in a table

gconf-service-backend package basic information: