gigsgigscloud 自带的CentOS 7.5系统比较坑，直接安装报错

Cannot retrieve metalink for repository: epel. Please verify its path and try again

要用yum需要先进行设置

vi /etc/resolv.conf

把nameserver改成8.8.8.8

service network restart   重启

之后运行

yum -y install wget      安装wget

yum update   升级下源

wget -N --no-check-certificate https://github.com/teddysun/across/raw/master/bbr.sh && chmod +x bbr.sh && bash bbr.sh
 安装BBR

如果CentOS 6系统执行以上操作不行还需要手工修改下注释，
打开vi /etc/yum.repos.d/epel.repo，将文件第3行注释去掉，把第四行注释掉。

[epel]
name=Extra Packages for Enterprise Linux 6 – $basearch
#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
修改为

[epel]
name=Extra Packages for Enterprise Linux 6 – $basearch
baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
再清理源，重新安装

yum clean all