mysqld與mysqld_safe

       mysqld, also known as MySQL Server, is the main program that does most

       of the work in a MySQL installation. MySQL Server manages access to the

       MySQL data directory that contains databases and tables. The data

       directory is also the default location for other information such as

       log files and status files.

實質上，用rpm或者yum這類包管理的工具，在linux下安裝時，所執行的 service mysqld start也就是啟動的這個程式。

而mysqld_safe呢？我man mysqld_safe了一下：

       mysqld_safe is the recommended way to start a mysqld server on Unix.

       mysqld_safe adds some safety features such as restarting the server

       when an error occurs and logging runtime information to an error log

       file. A description of error logging is given later in this section.

       mysqld_safe tries to start an executable named mysqld. To override the

       default behavior and specify explicitly the name of the server you want

       to run, specify a --mysqld or --mysqld-version option to mysqld_safe.

       You can also use --ledir to indicate the directory where mysqld_safe

       should look for the server.