切换root

chenwx@chenwx-virtual-machine:~$ su

Password:

su: Authentication failure

//切换失败

chenwx@chenwx-virtual-machine:~$ sudo passwd root

//修改密码

[sudo] password for chenwx:

//用户密码，也就是你的登机密码

Enter new UNIX password:

Retype new UNIX password:

//输入两次密码

passwd: password updated successfully

//修改成功

chenwx@chenwx-virtual-machine:~$ su

Password:

root@chenwx-virtual-machine:/home/chenwx#

//切换成功