[CentOS] how to set proxy systemwide (wget and docker)

Sat Jan 5 14:27:58 UTC 2019
Ralf Prengel <ralf.prengel at rprengel.de>

what is the right way to set a proxy systemwide using centos 7?
I need this for wget and docker. 
My first idea was /etc/environment but allthough the proxy is set wget and docker don‘ t connect to their target-systems.

Thanks for hints