Errors during downloading metadata for repository 'appstream':
- Status code: 404 for http://mirrors.cloud.aliyuncs.com/centos/8/AppStream/x86_64/os/repodata/repomd.xml....
Error: Failed to download metadata for repo 'appstream': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried
解决方法：直接跟着下面的命令复制即可
1.进入此目录
cd /etc/yum.repos.d/
2.
for i in `ls`;do sed -i 's/mirrors.cloud.aliyuncs.com/mirrors.aliyun.com/g' $i;done
for i in `ls`;do sed -i 's/$releasever/$releasever-stream/g' $i;done
3.清缓存
yum clean all
yum makecache
4.执行安装
yum -y install gcc-c++
