MySQL auto.cnf 文件

一、auto.cnf 是什么？

简介：MySQL启动时，会自动从data_dir/auto.cnf 文件中获取server-uuid值，并将这个值存储在全局变量server_uuid中。如果这个值或者这个文件不存在，那么将会生成一个新的uuid值，并将这个值保存在auto.cnf文件中。

源码解释：

/**
  File 'auto.cnf' resides in the data directory to hold values of options that
  server evaluates itself and that needs to be durable to sustain the server
  restart. There is only a section ['auto'] in the file. All these options are
  in the section. Only one option exists now, it is server_uuid.
  Note, the user may not supply any literal value to these auto-options, and
  only allowed to trigger (re)evaluation.
  For instance, 'server_uuid' value will be evaluated and stored if there is
  no corresponding line in the file.
  Because of the specifics of the auto-options, they need a seperate storage.
  Meanwhile, it