CentOS7 官方镜像源不可用问题解决方法

背景

我在安装python3.7.16时遇到了问题，发现是cenos7官方镜像源不可用。通过查找，用一下方式解决。

[root@yxf Python-3.7.16]# sudo yum makecache
Loaded plugins: fastestmirror
Determining fastest mirrors
Could not retrieve mirrorlist http://mirrorlist.centos.org?arch=x86_64&release=7&repo=sclo-rh error was
14: curl#6 - "Could not resolve host: mirrorlist.centos.org; Unknown error"


 One of the configured repositories failed (Unknown),
 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-rh/x86_64

我使用centos7时遇到了无法访问 mirrorlist.centos.org 的问题，因为CentOS 官方镜像源不可用。鉴于 CentOS 7 已经停止官方支持，推荐的解决方案是更换为更稳定的第三方镜像源，如阿里云、腾讯云或其他国内镜像源。

解决方案

1. 禁用有问题的仓库

首先，禁用导致问题的仓库（如 centos-sclo-rh），以避免它干扰其他操作：

sudo yum-config-manager --disable centos-sclo-rh

2. 配置阿里云镜像源

接下来，我们将配置阿里云镜像源来替代官方的 CentOS 镜像源。以下是具体步骤：

备份现有的仓库配置文件

在修改之前，建议备份现有的仓库配置文件：

sudo cp -a /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
sudo cp -a /etc/yum.repos.d/CentOS-SCLo-scl.repo /etc/yum.repos.d/CentOS-SCLo-scl.repo.bak

修改基础仓库配置

编辑或替换 /etc/yum.repos.d/CentOS-Base.repo 文件的内容为阿里云提供的 CentOS 7 源：

sudo tee /etc/yum.repos.d/CentOS-Base.repo <<-'EOF'
[base]
name=CentOS-$releasever - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/$releasever/os/$basearch/
gpgcheck=1
enabled=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

[updates]
name=CentOS-$releasever - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
gpgcheck=1
enabled=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

[extras]
name=CentOS-$releasever - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
gpgcheck=1
enabled=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

[centosplus]
name=CentOS-$releasever - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
EOF

添加 SCL 仓库配置

创建或编辑 /etc/yum.repos.d/CentOS-SCLo-scl.repo 文件，添加阿里云的 SCL 仓库配置：

sudo tee /etc/yum.repos.d/CentOS-SCLo-scl.repo <<-'EOF'
[centos-sclo-rh]
name=CentOS-7 - SCLo rh
baseurl=https://mirrors.aliyun.com/centos-vault/7.9.2009/sclo/x86_64/rh/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-SCLo

[centos-sclo-sclo]
name=CentOS-7 - SCLo sclo
baseurl=https://mirrors.aliyun.com/centos-vault/7.9.2009/sclo/x86_64/sclo/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-SIG-SCLo
EOF

3. 清理缓存并刷新元数据

完成上述配置后，清理所有缓存并重新加载仓库元数据：

sudo yum clean all
sudo yum makecache

总结

这样就可以解决该问题，继续使用centos7了。