1. 停止当前mysqld服务
`service mysql stop`

2. 用安全模式启动
`sudo mysqld_safe --skip-grant-tables--user=mysql&`

3. 无密码登陆
`mysql -u root`

4. 修改密码
```sql
FLUSH PRIVILEGES;
ALTER USER 'root'@'localhost' IDENTIFIED BY '密码';
EXIT;
```

5. 恢复正常mysql服务
```
sudo pkill mysqld
service mysql start
```