I just tested again, passwords length from 21 to 24, all can be used to login in tty7.

Maybe that day, I inputted the wrong password in tty7 login page.

I am always wrong. Sorry.

Exactly what happens when you try to log on to tty7 with a long password? It sounds as if it *might* be the GUI only allows you to enter 20 (or so) characters for the password (the programmers probably assumed no one would want to use a 24 char password). Does trying to log on produce a failed login reported in syslog or by lastb? If not the GUI might not be allowing you to try to log on.

Have you tried the same thing with tty1 to tty6?

I think (as in *seem to recall having read*) that tty7 is different from the rest ie: tty1 to tty6 in that it is usually taken by the Xorg display server.
This would mean that it is in use from the moment you logged in to your system.

Maybe the clue is there?

Best,

A.

Old password length = 20
New password length = 24

I cannot use the new password to login in tty7,
so I have to use the new password to login in tty1,
then I change the new password to the old password which length is 20.

I mean I cannot use a password which length is more than 20(?) to login in tty7.
Is there any other solution?

Thank you.