修改自己的密码（root用户，其它用户应该也差不多） 

方法一：

[root@localhost /]# mysqladmin -u root -p password "root"                           #修改密码为rootEnter password:                                                                     #输入旧密码[root@localhost /]# mysql -uroot -p #尝试使用旧密码登录 Enter password: ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES) [root@localhost /]# mysql -uroot -p #输入新密码root登录 Enter password: Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 19 Server version: 5.5.52-MariaDB MariaDB Server Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [(none)]>

方法二： 

在mysql.user中使用update更新密码 

方法三： 

或者进入mysql后，使用set修改密码

[root@localhost /]# mysql -uroot -p                         #使用旧密码root登录Enter password: Welcome to the MariaDB monitor.  Commands end with ; or \g. Your MariaDB connection id is 19 Server version: 5.5.52-MariaDB MariaDB Server Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [(none)]> set password=password("123456"); #修改密码为123456，我一直很好奇为什么密码必须用password扩起来，后来知道了，新密码必须用password来加密 Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> quit Bye [root@localhost /]# mysql -uroot -p #使用新密码123456登录 Enter password: Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 20 Server version: 5.5.52-MariaDB MariaDB Server Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [(none)]>

root用户修改指定用户密码

方法一

MariaDB [(none)]> set password for 'bp'@'localhost'=password("123456"); Query OK, 0 rows affected (0.01 sec)

方法二：

MariaDB [(none)]> update mysql.user set password=password("123") where user='bp' and host='localhost';                          #使用update修改密码，修改成功后，我打开另一个终端使用该用户登录数据库，发现无法使用新密码登录，但使用旧密码可以登录Query OK, 1 row affected (0.00 sec)Rows matched: 1 Changed: 1 Warnings: 0 MariaDB [(none)]> select user,host from mysql.user; #因为报错信息里面包含localhost，于是查看用户表信息有没有错，遗憾的是没有 +---------+-----------------------+ | user | host | +---------+-----------------------+ | aa | % | | aaa | % | | root | 127.0.0.1 | | root | ::1 | | | localhost | | aa | localhost | | bb | localhost | | bp | localhost | | ggo | localhost | | my | localhost | | mytest | localhost | | newuser | localhost | | nome | localhost | | root | localhost | | | localhost.localdomain | | root | localhost.localdomain | +---------+-----------------------+ 16 rows in set (0.00 sec) MariaDB [(none)]> flush privileges; #后来想起来，是不是还要刷新权限。刷新之后，使用新密码可以登录 Query OK, 0 rows affected (0.00 sec)

方法三：grant修改密码

MariaDB [mytest]> grant select on mytest.test to 'bp'@'localhost' identified by 'linux'; Query OK, 0 rows affected (0.05 sec) #这个不需要刷新权限。。

mysql5.7修改密码

cat /var/log/mysqld.log|grep 'temporary password'

alter user 'root'@'localhost' identified by 'root';

忘记密码（需要重启服务器）

在/etc/my.cnf的mysqld里面增加skip-grant-tables （5.7以前的应该是skip-grant）

重启mysqld

mysql> update mysql.user set authentication_string=password(',,,abc123...') where user='root';  （旧版的应该是update mysql.user set password=password(',,,abc123...') where user='root';）

Query OK, 1 row affected, 1 warning (0.00 sec)

Rows matched: 1 Changed: 1 Warnings: 1

mysql> flush privileges;

Query OK, 0 rows affected (0.00 sec)

mysql> quit

重启服务器