由于CentOS6的系统安装了epel-release-latest-7.noarch.rpm 导致在使用yum命令时出现Error: xz compression not available问题。
解决方法：
1.到https://centos.pkgs.org/7/epel-x86_64/epel-release-7-11.noarch.rpm.html下载epel-release-latest-7.noarch.rpm
2.卸载epel-release-latest-7.noarch.rpm：yum remove epel-release
3.清空epel目录：rm -rf /var/cache/yum/x86_64/6/epel/
4.安装epel6:rpm -ivh epel-release-latest-6.noarch.rpm
epel是什么 : https://www.cnblogs.com/fps2tao/p/7580188.html
转: https://blog.csdn.net/chenlix/article/details/52300906