The server was not allowing login to server even when ssh keys were saved

On rebooting server I could see it and error on screen “chown: Invalid username: root:Disk”

On troubleshooting found error to be due to corruption of /etc/passwd  as this is where all users are saved and due to corruption the user  root was missing in  /etc/passwd

So I got the serve in single user mode and fastboot as only single user mode wont server and would restart

Once I got access to single user I just moved the /etc/passwd to /etc/passwd.bkp and  copied  /etc/paswd.OLD which was in  /etc to /etc/passwd

Now on rebooting server i can see it working fine. 🙂