看CentOS或RedHat的版本

檢查CentOS的版本有下面幾種方法：

1. lsb_release -d
2. rpm --query centos-release
3. hostnamectl
4. cat /etc/centos-release
5. cat /etc/redhat-release 
6. cat /etc/system-release
7. cat /etc/os-release