My Raspberry Pi 4b changes password by itself

Question

I am using Raspbian Bullseye on my Raspberry Pi 4b, and in the last few days it has been changing the password by itself.

I have a headless setup, so I can only connect via SSH, and sometimes, several times a day, when I try to connect it just gives Permission denied, please try again.. I assumed a different issue at first, but after extracting the microSD and changing the /etc/shadow to some known password's hash I am able to gain access again, but this really gets in the way of work.

I know for a fact that I am not just forgetting the password, it is only one letter, I don't really need it very much at all, but this first happened when I was using a password-less setup.

What can be done?

Answer 1

The password is tested for complexity.
As a general guideline, passwords should consist of 6 to 8 characters including one or more characters from each of the following sets:
• lower case alphabetics
• digits 0 thru 9
• punctuation marks

passwd will reject any password which is not suitably complex.