https://hub.docker.com/_/centos/
for test purpose , we use docker to seperate os environments, so supported centos versions below:
latest, centos7, 7 (docker/Dockerfile) centos6, 6 (docker/Dockerfile) centos7.4.1708, 7.4.1708 (docker/Dockerfile) centos7.3.1611, 7.3.1611 (docker/Dockerfile) centos7.2.1511, 7.2.1511 (docker/Dockerfile) centos7.1.1503, 7.1.1503 (docker/Dockerfile) centos7.0.1406, 7.0.1406 (docker/Dockerfile) centos6.9, 6.9 (docker/Dockerfile) centos6.8, 6.8 (docker/Dockerfile) centos6.7, 6.7 (docker/Dockerfile) centos6.6, 6.6 (docker/Dockerfile)