Could someone verify this?
In UNIX systems you also have an important file called
/etc/shadow. Inside that file, you have encrypted password for each user. I think that you changed the files
/etc/passwd but forgot to change the
/etc/shadow. So now, you have changed a username, but you don't have actually a password for it. I am just theorizing here.
For example I created a
dummy account, with
dummy password. My contents of files are:
Now I will remove the entry from
/etc/shadow file. This is what I get:
Password: <I type dummy here>
su: Authentication failure
So there you have it. You should generate a proper hash for your new user and it to
/etc/shadow. Hope that helps.