A. mysqladmin
mysqladmin -u root -h localhost -p password 'rootroot'B.修改 mysql.user表
use mysql;
update mysql.user set authentication_string=PASSWORD('root') where user='root';
flush privileges;mysql root@localhost:(none)> set password=PASSWORD('root')D.使用 alter user
alter user 'root'@'localhost' identified by 'root'
alter user 'root'@'%' identified by 'root'

A.修改 mysql.user 表
use mysql;
update mysql.user set authentication_string=PASSWORD('itpux') where user='itpux' and host='localhost';
flush privileges;B.使用grant语句
grant usage on *.* to 'itpux'@'%' identified by 'root';
grant usage on *.* to 'itpux'@'localhost' identified by 'root';
flush privileges;C.当前用户登录(比如：itpux)
set password=PASSWORD('itpux')
D.使用 alter user(推荐)
alter user 'itpux'@'localhost' identified by 'root';
alter user 'itpux'@'%' identified by 'root';

mysql 5.7.11之前有一个360天密码过期的问题，5.7.12之后又改为密码不过期。
show variables like 'default_password_lifetime';mysql> show variables like 'default_password_lifetime';
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| default_password_lifetime | 0     |
+---------------------------+-------+A.永久：如果密码要设置过期或者不过期
my.cnf 参数
[mysqld]
default_password_lifetime=0 或 360B.水久：alter user
alter user 'itpux'@'localhost' password expire interval 90 day;
select * from mysql.user;
alter user 'itpux'@'localhost' password expire never;
alter user 'itpux'@'localhost' password expire DEFAULT;

alter user 'itpux'@'localhost' account lock;
alter user 'itpux'@'localhost' account unlock;

skip-grant-tablesor:mysqld --skip-grant-tablesuse mysql;
update mysql.user set authentication_string=PASSWORD('root') where user='root';
flush privileges;

1. service mysql stop
2.加入忽略授权表参数到my.cnf,改参数前备份原参数
[mysqld]
skip-grant-tables3. service mysql start4. mysql -uroot-p不用密码5.改密码
update mysql.user set authentication_string=PASSWORD('root') where user='root';
flush privileges;6.从my.cnf里面取消;
skip-grant-tables7. service mysql restart
8.登录测试

A mysql -uroot -p
B mysqL -p
C mysqL -S /mysql/data/3306/mysql.sock -uroot -p
D mysql -h ip -u root -p
E mysql -hlocalhost -uroot -proot
F mysql -uroot -p --defaults-file=/mysql/data/3306/my.cnf

[client]
user = "root"
password = "root"
登录方法：
mysql --defaults-file=/mysql/data/3306/my.cnf

[mysql]
user = "root"
password = "root"
[mysqladmin]
user = "root"
password = "root"

vi vim ~/.my.cnf
[client]
user = "root"
password = "root"

export MYSQL_PWD=root
登录方法：
mysql -uroot

[root@elasticsearch ~]# mysql_config_editor  set --login-path=itpuxpw --user=root --password
Enter password:
[root@elasticsearch ~]# mysql_config_editor print --all
[itpuxpw]
user = root
password = *****
[root@elasticsearch ~]# mysql --login-path=itpuxpw
清除
[root@elasticsearch ~]# mysql_config_editor remove --login-path=itpuxpw