Mysql的进程为什么会有两个,一个是mysqld_safe一个是mysqld？

[root@iZ2zed9zgziqo9et9ezfsjZ ~]# ps -ef | grep mysql
mysql 14522 1 0 Aug24 ? 00:00:00 /bin/sh /usr/bin/mysqld_safe --basedir=/usr
mysql 14685 14522 0 Aug24 ? 00:00:58 /usr/libexec/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --log-error=/var/log/mariadb/mariadb.log --pid-file=/var/run/mariadb/mariadb.pid --socket=/var/lib/mysql/mysql.sock
root 18208 18177 0 11:18 pts/0 00:00:00 grep --color=auto mysql