2020年11月30日 centos6各大开源镜像站已经停止维护了，但是阿里云还有其他源可以使用。

错误提示

 http://mirrors.aliyun.com/epel/6/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"

解决办法

cat /etc/yum.repos.d/CentOS-Base.repo 

# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#
 
[base]
name=CentOS-6.10 - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
 
#released updates 
[updates]
name=CentOS-6.10 - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
 
#additional packages that may be useful
[extras]
name=CentOS-6.10 - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
 
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-6.10 - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
 
#contrib - packages by Centos Users
[contrib]
name=CentOS-6.10 - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/6.10/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6

yum clean all
yum makecache