can't ssh into remote host with root, password incorrect

Question

I have a remote host, previously I can ssh into it with root and password

ssh root@remote_host

or I ssh into it first using a regular user account

ssh esolve@remote_host

and then su root and input password

but today, in both ways, my password is always incorrect, like

[esolve@local esolve]$  ssh root@remote_host
root@remote_host's password: 
Permission denied, please try again.

or

[esolve@remote_host ~]$ su root
Password: 
su: incorrect password

related information:

1. I can use this password to log in with root if I operated locally on that remote machine today.

2. I ssh into is via VPN

Why did this happen? How can I solve this problem?

Answer 1

Do you have ssh as root disabled? Check your sshd configuration (possibly /etc/ssh/sshd_config) and look for the line PermitRootLogin no. Change the no to yes and restart sshd (most likely either service ssh restart or service sshd restart).

Some distributions (e.g., Ubuntu) default to without-password for PermitRootLogin such that root login is allowed via public key authentication, but not with a password.

Answer 2

For first time if you are access SSH remote server in new system, just update it. Open the ssh configuration file,

# vim /etc/ssh/sshd_config

PermitRootLogin without-password

change to

PermitRootLogin yes

Restart your ssh service.

restart ssh server.

Answer 3

In my case, this 73rd line in sshd_config didn't allow any user to login with password. No where found this solution, just struck it with luck. Either comment it out (or make it 'yes'):

KbdInteractiveAuthentication no

This prohibits keyboard interaction while logging into remote server.