先说，改文件之前做好备份！！！

编辑 /etc/yum.repos.d/CentOS-Base.repo

[C6.10-base]
name=CentOS-6.10 - Base
baseurl=http://vault.centos.org/6.10/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
enabled=1
metadata_expire=never

[C6.10-updates]
name=CentOS-6.10 - Updates
baseurl=http://vault.centos.org/6.10/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
enabled=1
metadata_expire=never

[C6.10-extras]
name=CentOS-6.10 - Extras
baseurl=http://vault.centos.org/6.10/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
enabled=1
metadata_expire=never

[C6.10-contrib]
name=CentOS-6.10 - Contrib
baseurl=http://vault.centos.org/6.10/contrib/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
enabled=0
metadata_expire=never

[C6.10-centosplus]
name=CentOS-6.10 - CentOSPlus
baseurl=http://vault.centos.org/6.10/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
enabled=0
metadata_expire=never

编辑 /etc/yum.repos.d/epel.repo

[epel]
name=Extra Packages for Enterprise Linux 6 - $basearch
#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
baseurl=https://archives.fedoraproject.org/pub/archive/epel/6/x86_64
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6

[epel-debuginfo]
name=Extra Packages for Enterprise Linux 6 - $basearch - Debug
#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch/debug
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-debug-6&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
gpgcheck=1

[epel-source]
name=Extra Packages for Enterprise Linux 6 - $basearch - Source
#baseurl=http://download.fedoraproject.org/pub/epel/6/SRPMS
baseurl=https://archives.fedoraproject.org/pub/archive/epel/6/SRPMS
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-source-6&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
gpgcheck=1

最后，

yum clean all && yum makecache

参考：

https://www.getpagespeed.com/server-setup/how-to-fix-yum-after-centos-6-went-eol