我道歉。。我知道这个问题以前被问过很多次，但我试过很多建议，根本找不到解决办法。
问题是，当我尝试在workbench上连接时，会出现以下错误：
“无法使用用户root在127.0.0.1:3306连接到mysql”
但如果我跑了 shell> mysqladmin version ，我得到：

mysqladmin Ver 8.42 Distrib 5.7.19, for Linux on x86_64 
Copyright (c) 2000, 2017, 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. 
Server version  5.7.19 
Protocol version    10 
Connection  Localhost via UNIX socket 
UNIX socket /var/run/mysqld/mysqld.sock 
Uptime: 32 sec 
Threads: 1 Questions: 3 Slow queries: 0 Opens: 107 Flush tables: 1 Open 
tables: 26 Queries per second avg: 0.093

以下命令也可以正常运行：

shell> mysqld (service is running)
shell> mysql (login on Server)

wb上的“newconnection”设置为：

Connection Method: Standard (TCP/IP)
Parameters.Hostname: 127.0.0.1 - Port: 3306
Parameters.Username: root
... (next values are by Default)

我的系统是ubuntu 14.04 lts。
提前谢谢。