最近在fedora中yum install gdb时报错：
Failed to download metadata for repo 'fedora-modular'
Error: Failed to download metadata for repo 'fedora-modular'
解决方案1：
在/etc/dnf/dnf.conf结尾添加sslverify=0
参考：
http://fossdev.blogspot.com/2015/12/fedora-update-with-dnf-cannot.html
解决方案2：
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：
https://blog.csdn.net/kajweb/article/details/80202175