Fedora OS，设置了代理后，yum -y install vim失败，解决办法：

报错信息：

Fedora Modular 31 - x86_64 12 B/s | 19 B 00:01
Errors during downloading metadata for repository 'fedora-modular':
- Status code: 404 for http://download.fedoraproject.org/pub/fedora/linux/releases/31/Modular/x86_64/os/repodata/repomd.xml (IP: 10.239.4.100)
Error: Failed to download metadata for repo 'fedora-modular': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

 解决办法：

需替换fedora下载源以及更新 源：

# su
# cd /etc/yum.repos.d/
# mv fedora.repo fedora.repo.backup
# mv fedora-updates.repo fedora-updates.repo.backup
# wget -O /etc/yum.repos.d/fedora.repo http://mirrors.aliyun.com/repo/fedora.repo
# wget -O /etc/yum.repos.d/fedora-updates.repo http://mirrors.aliyun.com/repo/fedora-updates.repo
# dnf clean all
# dnf makecache

参考链接：https://www.jianshu.com/p/79906aca03e0（有更过解决方法汇总）