Problem

You’re running behind a corporate proxy server and you need docker to be able to pull images on CentOS 7 (or any other systemd based distro).

Setting the environment variable http_proxy or https_proxy isn’t working.

Solution for systemd based Linux distributions

CentOS changed their init system to systemd in version 7 and that means to solve this problem you need to make a new file at: /etc/systemd/system/docker.service.d/http-proxy.conf

The contents should contain your proxy server details. Here’s mine:

[Service]
Environment="HTTP_PROXY=http://127.0.0.1:8000/"
Environment="HTTPS_PROXY=https://127.0.0.1:8000/"

More

Full docs from Docker are currently available at https://docs.docker.com/engine/admin/systemd/