CentOS 7 YUM 源配置修复文档

问题现象

CentOS 7 系统使用 yum 安装软件时出现错误：

[root@test conf.d]# yum makecache
已加载插件：fastestmirror, product-id, search-disabled-repos, subscription-manager

This system is not registered with an entitlement server. You can use subscription-manager to register.

Determining fastest mirrors


 One of the configured repositories failed (未知),
 and yum doesn't have enough cached data to continue. At this point the only
 safe thing yum can do is fail. There are a few ways to work "fix" this:

     1. Contact the upstream for the repository and get them to fix the problem.

     2. Reconfigure the baseurl/etc. for the repository, to point to a working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages for the previous distribution release still work).

     3. Run the command with the repository temporarily disabled
            yum --disablerepo=<repoid> ...

     4. Disable the repository permanently, so yum won't use it by default. Yum
        will then just ignore the repository until you permanently enable it
        again or use --enablerepo for temporary usage:

            yum-config-manager --disable <repoid>
        or
            subscription-manager repos --disable=<repoid>

     5. Configure the failing repository to be skipped, if it is unavailable.
        Note that yum will try to contact the repo. when it runs most commands,
        so will have to try and fail each time (and thus. yum will be be much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:

            yum-config-manager --save --setopt=<repoid>.skip_if_unavailable=true

Cannot find a valid baseurl for repo: centos-sclo-sclo

解决方案

步骤1：清理现有仓库配置

进入仓库配置目录

cd /etc/yum.repos.d

备份所有现有仓库文件

mkdir -p backup_all

移动所有 .repo 文件到备份目录

mv *.repo backup_all/

验证备份结果

ls -la backup_all/

步骤2：下载阿里云镜像源

重新下载阿里云 CentOS 7 仓库配置（使用 HTTP 协议）

curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

验证文件是否下载成功

ls -l /etc/yum.repos.d/CentOS-Base.repo

步骤3：检查仓库配置文件内容

查看配置文件前50行内容

head -50 /etc/yum.repos.d/CentOS-Base.repo

检查镜像列表和基础URL配置

grep -n "mirrorlist\|baseurl" /etc/yum.repos.d/CentOS-Base.repo | head -20

步骤4：备份并修改阿里云源配置

备份阿里云源配置文件

cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

禁用 mirrorlist（避免DNS解析问题）

sed -i 's/^mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-Base.repo

启用 baseurl 并确保使用 HTTP 协议

sed -i 's@^#baseurl=.*/centos/@baseurl=http://mirrors.aliyun.com/centos/@g' /etc/yum.repos.d/CentOS-Base.repo

步骤5：添加 EPEL 扩展仓库

下载 EPEL（Extra Packages for Enterprise Linux）仓库配置

curl -o /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo

如果需要，同样修改 EPEL 仓库配置

sed -i 's/^mirrorlist/#mirrorlist/g' /etc/yum.repos.d/epel.repo
sed -i 's@^#baseurl=.*/epel/@baseurl=http://mirrors.aliyun.com/epel/@g' /etc/yum.repos.d/epel.repo

步骤6：清理 YUM 缓存并测试

清理所有 YUM 缓存

yum clean all

重建缓存

yum makecache

测试安装软件（示例：安装 lrzsz）

yum install -y lrzsz

验证安装结果

which rz which sz