简介
刚刚使用 yum 下载某工具时，报下面这个错误，意思时 yum 的镜像源不能用了。
[root@localhost build]# yum install -y centos-release-scl
Loaded plugins: fastestmirror, langpacks
Determining fastest mirrors
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock 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: base/7/x86_64
解决
这是因为 CentOS 7 在 2024 年 6 月 30 日停止官方支持（EOL），mirrorlist.centos.org 源已下线不可用。
按照下面的操作解决，先备份原来的源文件，再添加一个新的镜像源。
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
敲下面的命令，添加新的镜像源（阿里云的）。
cat > /etc/yum.repos.d/CentOS-Base.repo <<EOF
> [base]
> name=CentOS-7 - Base - mirrors.aliyun.com
> baseurl=http://mirrors.aliyun.com/centos-vault/7.9.2009/os/x86_64/
> gpgcheck=1
> gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
>
> [updates]
> name=CentOS-7 - Updates - mirrors.aliyun.com
> baseurl=http://mirrors.aliyun.com/centos-vault/7.9.2009/updates/x86_64/
> gpgcheck=1
> gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
>
> [extras]
> name=CentOS-7 - Extras - mirrors.aliyun.com
> baseurl=http://mirrors.aliyun.com/centos-vault/7.9.2009/extras/x86_64/
> gpgcheck=1
> gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
> EOF
再清除之前的缓存，重新建立缓存。
yum clean all
yum makecache
上面的操作都做完后，再执行前面的下载命令，这回可以了。
