See the other thread. All is made clear there.

Assuming you trying to log in as "lfs" user using root password (that one you had changed recently).
Boot your system. When you will be asked for login, type "root" and hit Enter key. Being asked for password, type the password you had changed recently. Press Enter key. If you successfully logged in, run this command:
it will show content of /home directory. /home has a subdirectory matches your user name. You must use it as your user name. Let say it's name is "lfs" as you expecting it. Reset (set new password) for this user by running:
Once you will change user password, type "exit" and press Enter. You will be logged out. Now log in as "lfs" user with new "lfs" user's password.


I'm wondering how did you install LFS if you even can't log in and reset password?

Just FYI, there is no regular user yet at the point where this person is working. The /home directory is completely empty at this point. A newly finished LFS system has only the root user.
Except for a set of temporary compiling tools, an LFS system is built entirely in a chroot environment in a host system.

My assumption is he could create user account and that is why I suggested to check /home directory.
Nobody knows for sure whether he has user account or not (including OP itself since he tries to log in). Once he forgot a password he could forgot a user as well, isn't it? So ls /home is just a test for user existence.

And yes, thanks for remembering about chroot, I just forgot that my system built in the same way...

You're right. He could have created a user account without mentioning it.
In basan46's other thread on this matter (this one is a re-animated zombie-necro), it's clearer that he simply became confused and thought the "lfs" user in the host system was somehow present in the newly created LFS system.