centos遇到Could not resolve host: mirrorlist.centos.org; 未知的错误"

[root@localhost ~]# sed -i s/mirror.centos.org/vault.centos.org/g /etc/yum.repos.d/*.repo
[root@localhost ~]# sed -i s/^#.*baseurl=http/baseurl=http/g /etc/yum.repos.d/*.repo
[root@localhost ~]# sed -i s/^mirrorlist=http/#mirrorlist=http/g /etc/yum.repos.d/*.repo
[root@localhost ~]# sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*
[root@localhost ~]# sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*