Get https://index.docker.io/v1/repositories/library/centos/images: dial tcp: lookup index.docker.io: Temporary failure in name resolution

报错：

# docker pull centos:6.8
Pulling repository centos
Get https://index.docker.io/v1/repositories/library/centos/images: dial tcp: lookup index.docker.io: Temporary failure in name resolution

解决：

重新登录一下