There are two ways to cancel the root password.One is to use the passwd command with the - d parameter to delete the password.Usage example: $passwd - d root The other is to edit the/etc/shadow file directly. The/etc/shadow file stores the passwords of each user in an encrypted form. If the password is empty, you are not allowed to log in with a password.Usage example: $sudo nano/etc/shadow Delete the content between the first and second colons in the root line
There is no limit for ordinary users. You can set up an account, but you must have a password.You can use ssh or telnet to log in, provided that you have opened the ssh or telnet service.
