裝完數據庫清理一些默認賬號的時候不小心把root刪除了，flush privileges 之后的新 root 忘了grant任何權限，查看mysqld選項里面有個 −−skip-grant-tables

mysql5.5手冊說明如下

This option causes the server to start without using the privilege system at all, which gives anyone with access to the server unrestricted access to all databases. You can cause a running server to start using the grant tables again by executing mysqladmin flush-privileges or mysqladmin reload command from a system shell, or by issuing a MySQL FLUSH PRIVILEGES statement after connecting to the server. This option also suppresses loading of plugins, user-defined functions (UDFs), and scheduled events. To cause plugins to be loaded anyway, use the --plugin-load option.

--skip-grant-tables is unavailable if MySQL was configured with the --disable-grant-options option. See Section 2.10.2, “Typical configure Options”.

mysqld_safe是Unix/Linux系統下的MySQL服務器的一個啟動腳本。這個腳本增加了一些安全特性，會在啟動MySQL服務器以后繼續監控其運行情況，并在出現錯誤的時候重新啟動服務器。后臺啟動mysql

如果沒有root賬戶就添加一個

直接輸入mysql連接并添加權限，這時候是不能使用grant命令的，只能用update

注意我用的是mysql是5.5版本，可能操作過程中sql語句或其他地方有不同，語句執行完畢之后需要flush privileges ，還可能要重新登錄才行。