目录在：/etc/yum.repos.d
[root@gip yum.repos.d]# pwd
/etc/yum.repos.d
[root@gip yum.repos.d]# ls
bak CentOS-Base.repo
[root@gip yum.repos.d]# cat 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-$releasever - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/http://mirrors.aliyuncs.com/centos/$releasever/os/$basearch/http://mirrors.cloud.aliyuncs.com/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7#released updates
[updates]
name=CentOS-$releasever - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/http://mirrors.aliyuncs.com/centos/$releasever/updates/$basearch/http://mirrors.cloud.aliyuncs.com/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/http://mirrors.aliyuncs.com/centos/$releasever/extras/$basearch/http://mirrors.cloud.aliyuncs.com/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/http://mirrors.aliyuncs.com/centos/$releasever/centosplus/$basearch/http://mirrors.cloud.aliyuncs.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/contrib/$basearch/http://mirrors.aliyuncs.com/centos/$releasever/contrib/$basearch/http://mirrors.cloud.aliyuncs.com/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7将/etc/yum.repos.d目录下的： CentOS-Base.repo 修改成上边的内容。（最好将原来的文件本地先做个备份）
#更新缓存
yum clean all
yum makecache
通过yum list available检查是否可用。
如果以后安装软件时，遇到问题，再将其它的repo文件从bak文件中考出来。
附：常见的国内 CentOS 镜像源地址：
阿里云镜像：
基础仓库 (Base):
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/ mirrorlist=https://mirrors.aliyun.com/repo/Centos-$releasever/base/更新仓库 (Updates):
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/ mirrorlist=https://mirrors.aliyun.com/repo/Centos-$releasever/updates/额外仓库 (Extras):
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/ mirrorlist=https://mirrors.aliyun.com/repo/Centos-$releasever/extras/
清华大学镜像站：
基础仓库 (Base):
baseurl=http://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/os/$basearch/
更新仓库 (Updates):
baseurl=http://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/updates/$basearch/
额外仓库 (Extras):
baseurl=http://mirrors.tuna.tsinghua.edu.cn/centos/$releasever/extras/$basearch/
腾讯云镜像：
基础仓库 (Base):
baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/os/$basearch/
更新仓库 (Updates):
baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/updates/$basearch/
额外仓库 (Extras):
baseurl=http://mirrors.cloud.tencent.com/centos/$releasever/extras/$basearch/
华为云镜像：
基础仓库 (Base):
baseurl=https://repo.huaweicloud.com/centos/$releasever/os/$basearch/
更新仓库 (Updates):
baseurl=https://repo.huaweicloud.com/centos/$releasever/updates/$basearch/
额外仓库 (Extras):
baseurl=https://repo.huaweicloud.com/centos/$releasever/extras/$basearch/
中国科学技术大学镜像：
基础仓库 (Base):
baseurl=http://mirrors.ustc.edu.cn/centos/$releasever/os/$basearch/
更新仓库 (Updates):
baseurl=http://mirrors.ustc.edu.cn/centos/$releasever/updates/$basearch/
额外仓库 (Extras):
baseurl=http://mirrors.ustc.edu.cn/centos/$releasever/extras/$basearch/
请注意，上面的 $releasever 和 $basearch 是占位符，它们代表你的 CentOS 版本和架构。例如，在 CentOS 7 中，$releasever 将是 7，而 $basearch 通常是 x86_64。
当在 /etc/yum.repos.d/CentOS-Base.repo 文件中使用这些地址时，记得更新这些变量以匹配你的系统环境。例如，对于阿里云镜像的基础仓库，将这样设置：
[base]
name=CentOS-$releasever - Base - mirrors.aliyun.com
mirrorlist=https://mirrors.aliyun.com/repo/Centos-$releasever/base/
#baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
可以选择其中一个镜像源，将其地址复制粘贴到你的 CentOS-Base.repo 文件中，然后根据实际的 CentOS 版本和架构进行调整。
