I cannot reset password using rescue mode

We have a problem on a centos 6 server. normally, PasswordAuthentication is off. When I get connected using rescue mode, I execute these commands : mount -o remount,rw / chroot / /bin/bash passwd root It says password reset successfully. And I also try to edit /etc/ssh/sshd_config and /etc/ssh/ssh_config to enable password authentication, but the problem is that none of the modifications is saved after reboot. And when I try the new password with ssh, it does not work. Do you have any idea?