systemdのserviceの下に追記
[root@centos ~]# vim /usr/lib/systemd/system/docker.service
[Service]
Environment="HTTP_PROXY=proxy.si1230.com:3128"
Environment="HTTPS_PROXY=proxy.si1230.com:3128"
Environment="NO_PROXY=localhost,192.168.0.0/16"
systemdを変更したのでdaemon-reload
[root@centos ~]# systemctl daemon-reload
docker再起動
[root@centos ~]# systemctl restart docker.service
Docker プロキシ設定