How to remove linux root password?

Question

linux

I go to GNU GRUB (version 1.99-12ubuntu5) > went to the recovery mode section> then root> I write: passwd username> a footcloth opens with commands, from all commands I'm interested in -delete> I write: passwd [-d] [username]> crashes message change to MAX_DAYS and after that my work stopped, because I don't know what value to drive.
I tried to write: passwd [-x 3] [username] and passwd [-x MAX_3] in general, I don’t know how to do it correctly, there is no such information in the manuals.

Answer 1

So reset the password for root or delete?
Please provide console output.
And it confuses me that you write that you have a command like this "passwd [-d] [username]"
do you write it right?
Maybe it is necessary
passwd -d root
But what is the goal?