1. 查看日志
151101 17:07:02 InnoDB: Completed initialization of buffer pool
151101 17:07:02 InnoDB: Fatal error: cannot allocate memory for the buffer pool
151101 17:07:02 [ERROR] Plugin ‘InnoDB‘ init function returned error.
151101 17:07:02 [ERROR] Plugin ‘InnoDB‘ registration as a STORAGE ENGINE failed.
151101 17:07:02 [ERROR] Unknown/unsupported storage engine: InnoDB
151101 17:07:02 [ERROR] Aborting
151101 17:07:02 [Note] /alidata/server/mysql/bin/mysqld: Shutdown complete
发现错误
2. 清理内存
free -m
echo 1 > /proc/sys/vm/drop_caches
3. 修改配置
vi /etc/my.cnf
innodb_buffer_pool_size = 16M -- 小于可用内存
4. 启动MySQL
service mysqld start
MySQL: The server quit without updating PID file
原文：http://my.oschina.net/maczhao/blog/524601