unable to login as root

Root login should work in Webmin, Webshell, SSH and SFTP. If you are trying to login to the WebUI of a specific webapp (e.g. WrodPress, Joomla, Drupal, etc) then root will not work. You'll need to use whatever admin account is relevant to the specific app (see the relevant appliance page for details, generally it will either be 'admin' or email address configured on firstboot).

Just having reread your post however it sounds like you are trying to log in via SSH (or local terminal). Is that right? Depending on where the system is running you may be able to reset the root password. If you can get access to a local terminal during boot then this should help (Proxmox is Debian based, same as TurnKey).

Without some more diagnosis I have no idea what the problem might be though...

Is this a new install? If so I'd check that the ISO (or VMDK or whatever build you are using) is not corrupted. And assuming that it's not I'd just do a clean install. Obviously if you have data in there then that may not be an option (unless you have a recent backup).

Did you try resetting the root password as described in that link?

Thanks for your reply,

I am trying to login using turnkey linux terminal(installed in virtual box).

when I enter credentails root and password normal message appears and disappears in a second and again asks for credentials like a loop. If I try that in putty, putty window disappears(closes) automatically.

other than that I have a another user on this machine, I can login as that user normally.

I would say it is login problem.

Please sugggest me how can I fix this issue.

Thanks,

Harish.