原因：https://wiki.centos.org/About/Product?spm=a2c4g.11174386.n2.3.605e1d82pphpDY%3E
解决方法：
1、关闭fastestmirror
sed -i 's/enabled=1/enabled=0/' /etc/yum/pluginconf.d/fastestmirror.conf
2、yum源备份
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
3、更新新源
cat >> /etc/yum.repos.d/CentOS-Base.repo << EOF
# 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 - vault.centos.org
failovermethod=priority
baseurl=http://vault.centos.org/6.10/os/$basearch/
gpgcheck=1
gpgkey=http://vault.centos.org/RPM-GPG-KEY-CentOS-6
#released updates
[updates]
name=CentOS-6.10 - Updates - vault.centos.org
failovermethod=priority
baseurl=http://vault.centos.org/6.10/updates/$basearch/
gpgcheck=1
gpgkey=http://vault.centos.org/RPM-GPG-KEY-CentOS-6
#additional packages that may be useful
[extras]
name=CentOS-6.10 - Extras - vault.centos.org
failovermethod=priority
baseurl=http://vault.centos.org/6.10/extras/$basearch/
gpgcheck=1
gpgkey=http://vault.centos.org/RPM-GPG-KEY-CentOS-6
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-6.10 - Plus - vault.centos.org
failovermethod=priority
baseurl=http://vault.centos.org/6.10/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://vault.centos.org/RPM-GPG-KEY-CentOS-6
#contrib - packages by Centos Users
[contrib]
name=CentOS-6.10 - Contrib - vault.centos.org
failovermethod=priority
baseurl=http://vault.centos.org/6.10/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://vault.centos.org/RPM-GPG-KEY-CentOS-6
EOF
或者这个方法
https://www.getpagespeed.com/server-setup/how-to-fix-yum-after-centos-6-went-eol