Determining fastest mirrors
YumRepo Error: All mirror URLs are not using ftp, http[s] or file.
Eg. Invalid release/repo/arch combination/
removing mirrorlist with no valid mirrors: /var/cache/yum/i386/6/base/mirrorlist.txt
Error: Cannot find a valid baseurl for repo: base
在网上找了很多的方法，但是都不起作用：
最终解决方案：
#sed -i "s|enabled=1|enabled=o|g" /etc/yum/pluginconf.d/fastestmirror.conf
#mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/Centos-Base.repo.backup
#curl -o /etc/yum.repos.d/centos-Base.repo https://www.xmpan.com/Centos-6-Vault-Aliyun.repo
#yum clean all
依次执行完上述命令，再执行yum -y install gcc*就没有报错了。