由於CentOS6的系統安裝了epel-release-latest-7.noarch.rpm 導致在使用yum命令時出現Error: xz compression not available問題。
解決方法：
1.到https://centos.pkgs.org/7/epel-x86_64/epel-release-7-11.noarch.rpm.html下載epel-release-latest-7.noarch.rpm
2.卸載epel-release-latest-7.noarch.rpm：yum remove epel-release
3.清空epel目錄：rm -rf /var/cache/yum/x86_64/6/epel/
4.安裝epel6:rpm -ivh epel-release-latest-6.noarch.rpm
epel是什么 : https://www.cnblogs.com/fps2tao/p/7580188.html
轉: https://blog.csdn.net/chenlix/article/details/52300906