FROM ubuntu:16.04
RUN apt update && apt-get -y install gconf-service

docker build -t foo .
docker run -it foo bash

root@c5cc80362316:/# gconf-service
bash: gconf-service: command not found
root@c5cc80362316:/# which gconf-service
root@c5cc80362316:/# echo $?
1
root@c5cc80362316:/# apt list --installed | grep gconf-service

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

gconf-service/xenial,now 3.2.6-3ubuntu6 amd64 [installed]
gconf-service-backend/xenial,now 3.2.6-3ubuntu6 amd64 [installed,automatic]