在Linux中有時安裝Mysql會出現沒有root使用者的狀況，或者說root賬戶被從mysql.user表中誤刪除，這樣就導致很多許可權無法控制。解決辦法是重新建立root使用者，並授予所有許可權，具體方法如下：

1. 修改/etc/my.conf檔案，新增skip-grant-tables

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

skip-grant-tables
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid

/etc/init.d/mysqld restart

mysql

use mysql;
insert into user set user='root',ssl_cipher='',x509_issuer='',x509_subject='';
update user set Host='localhost',select_priv='y', insert_priv='y',update_priv='y', Alter_priv='y',delete_priv='y',create_priv='y',drop_priv='y',reload_priv='y',shutdown_priv='y',Process_priv='y',file_priv='y',grant_priv='y',References_priv='y',index_priv='y',create_user_priv='y',show_db_priv='y',super_priv='y',create_tmp_table_priv='y',Lock_tables_priv='y',execute_priv='y',repl_slave_priv='y',repl_client_priv='y',create_view_priv='y',show_view_priv='y',create_routine_priv='y',alter_routine_priv='y',create_user_priv='y' where user='root';

先退出：quit;

mysql -u root
update mysql.user set password=password('yourrootpasswd') where user='root';
update user set host = '%' where user = 'root'; #設定遠端機器可訪問mysql，如果不需要可不是設定
flush privileges;
quit;

/etc/init.d/mysqld restart