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

gconf-defaults-service is installed in your system.

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

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

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

gconf-defaults-service package basic information: