现象：
Warning: PID file not written; -detached was passed.
ERROR: epmd error for host abcdefg: timeout (timed out)
原因：
其实RabbitMQ报这个错的原因是无法在/etc/hosts中正确识别主机名，因此只需修改该文件即可
解决办法：
vim /etc/hosts
127.0.0.1 abcdefg localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6