I can't log in to the root account after installing ubuntu

After ubuntu is installed, the authentication failure will be displayed when logging in to the root account, as follows:

In fact, Ubuntu does not have a password just after installing the image. After logging in to the account you created, you need to set the password for the root account;

Here's how to do it:

Enter in your own user's command interface:

sudo passwd and then enter the password setting interface, you can set your own root account password:

After setting up, you can su root and enter the password you just set to switch to the root user.