How to use systemctl in Ubuntu 14.04

Question

I try to perform the following command in Ubuntu 14.04:

systemctl enable --now docker-cleanup-dangling-images.timer

I also tried it with sudo,

Answer 1

So you want to remove dangling images? Am I correct?

systemctl enable docker-container-cleanup.timer
systemctl start docker-container-cleanup.timer
systemctl enable docker-image-cleanup.timer 
systemctl start docker-image-cleanup.timer

https://github.com/larsks/docker-tools/tree/master/docker-maintenance-units