如果不记得MysqL的root密码，那么就只能强制修改密码了，使用shell轻松自动修改密码:

#!/bin/bash
#Author Aiker
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
export PATH
read -p "Please input your new password:" c
pwd=$c
service MysqLd stop
MysqLd_safe --skip-grant-tables&
echo '正在修改密码...';
echo 'The set password...';
sleep 6
MysqL -uroot -e "insert into MysqL.user(Select_priv,Insert_priv,Update_priv,Delete_priv,Create_priv,Drop_priv,Reload_priv,Shutdown_priv,Process_priv,File_priv,Grant_priv,References_priv,Index_priv,Alter_priv,Show_db_priv,Super_priv,Create_tmp_table_priv,Lock_tables_priv,Execute_priv,Repl_slave_priv,Repl_client_priv,Create_view_priv,Show_view_priv,Create_routine_priv,Alter_routine_priv,Create_user_priv,Event_priv,Trigger_priv,Create_tablespace_priv,User,Password,host)values('Y','Y','root',password('${pwd}'),'127.0.0.1')"
MysqL -uroot -e "insert into MysqL.user(Select_priv,'localhost')"
MysqL -uroot -e "UPDATE MysqL.user SET password=PASSWORD('${pwd}') WHERE user='root'";
MysqL -uroot -e "UPDATE MysqL.user SET authentication_string=PASSWORD('${pwd}') WHERE user='root'";
MysqL -uroot -e "FLUSH PRIVILEGES";
pkill -9 MysqLd_safe
pkill -9 MysqLd
sleep 2
service MysqLd start

echo '==========================================='
echo "MysqL root密码成功修改为: ${pwd}"
echo "The root password set ${pwd}  successuful"

测试效果：

[root@aaa ~]# sh MysqLpwd.sh 
Please input your new password:12345678
Shutting down MysqL.. SUCCESS! 
正在修改密码...
The set password...
2018-03-14T18:19:51.793872Z MysqLd_safe Logging to '/data/MysqL/aaa.err'.
2018-03-14T18:19:51.814649Z MysqLd_safe Starting MysqLd daemon with databases from /data/MysqL
ERROR 1054 (42S22) at line 1: Unknown column 'Password' in 'field list'
ERROR 1054 (42S22) at line 1: Unknown column 'Password' in 'field list'
ERROR 1054 (42S22) at line 1: Unknown column 'password' in 'field list'
MysqLpwd.sh: line 17: 45426 Killed                  MysqLd_safe --skip-grant-tables
Starting MysqL SUCCESS! 
===========================================
MysqL root密码成功修改为: 12345678
The root password set 12345678  successuful
[root@aaa ~]# MysqL -uroot -p         
Enter password: 
Welcome to the MysqL monitor.  Commands end with ; or \g.
Your MysqL connection id is 2
Server version: 5.7.21-log Source distribution

Copyright (c) 2000,2018,Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MysqL> quit
Bye