Cannot login as root to centos server

I used to login as ssh root@servip with a password authentication into my CentOS 6 server.

I am not sure if what I have done has caused this, but while trying to get over my problem of accessing webmin remotely I followed the following tutorial until I reached:

adding auth required pam_google_authenticator.so into /etc/pam.d/sshd. Then by mistake, I have closed the ssh session. When I tried to login in back with the usual password, I get: Permission denied, please try again error. How can I get over this problem?

I don’t have a physical access to the server.

Switch to the second ssh session that you should have opened, and fix it. The howto did explicitly warn you to do this, exactly because of the possibility of something like this happening.

At this point the only way you can recover is via the system console. If you don’t have remote access to the console, e.g. with DRAC, iLO, IPMI, etc., you will have to physically visit the server.

Check more discussion of this question.

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