yum makecache或者yum install gcc 报错：

https://vault.centos.org/6.4/os/x86_64/repodata/repomd.xml: [Errno 14] problem making ssl connection
Trying other mirror.

后来查阅资料(/FAQ/General)，是停止维护了

CentoS 6 停止维护更新日期2020年11月30日

CentOS 7 停止维护更新日期2021年6月30日

CentOS 8 停止维护更新日期2021年12月31日

解决方式：

还有一个阿里云源(centos-vault)可以使用，整理内容如下，直接复制可用。

# 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-6.4 - Base
baseurl=http://mirrors.aliyun.com/centos-vault/6.4/os/x86_64/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
 
[updates]
name=CentOS-6.4 - Updates
baseurl=http://mirrors.aliyun.com/centos-vault/6.4/updates/x86_64/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
 
[extras]
name=CentOS-6.4 - Extras
baseurl=http://mirrors.aliyun.com/centos-vault/6.4/extras/x86_64/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
 
[centosplus]
name=CentOS-6.4 - Plus
baseurl=http://mirrors.aliyun.com/centos-vault/6.4/centosplus/x86_64/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6
 
[contrib]
name=CentOS-6.4 - Contrib
baseurl=http://mirrors.aliyun.com/centos-vault/6.4/contrib/x86_64/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-6

 OK，问题解决~