i am beginner with centos - Linux i have dedicated server . my root username is bnroot . now i am taking ssh using this user. i want to disable ssh for bnroot. i have created user user name welcome i want take ssh login by welcome user then i ll use su - bnroot to get root privileges. i have set PermitRootLogin no , AllowUsers welcome IN /etc/sshd_config and after restarting sshd service . i take ssh login by welcome use then it is ok. but when i use su bnroot its prompt to password and i enter right passowrd it show su: incorrect password , i dont know where i am wrong . please help me here. changes i done - /etc/ssh/sshd_confid PermitRootLogin no AllowUsers welcome /etc/sudoers welcome ALL=(ALL) ALL getting error in /var/log/secure unix_chkpwd[666]: password check failed for user (bnroot) su: pam_unix(su:auth): authentication failure; logname=ewalletssh uid=503 euid=500 tty=pts/1 ruser=ewalletssh rhost= user=bnroot please let me know where i am wrong