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I have a small embedded device that runs Linux and an SSH server. This box is set up with one user (root) and no password whatsoever.

Currently, there is one Windows XP-based laptop that is used to run diagnostics on the embedded device. When attempting to SSH into the device from the laptop, the user is prompted for a password, even though there isn't one associated with root. From any other computer, SSH correctly logs in sans password.

On the laptop, this behavior is exhibited when using putty, cygwin, and a virtual machine. Again, on any other computer, this exact same VM will connect via SSH successfully without a password.


It's clear that I don't have a firm grasp on Linux/SSH's ideas of password requirements.

As I said, though, from any other device, ssh root@DEVICEIP will log in without a password once the device's key is stored. It's only this one laptop (and any method of using SSH on this laptop) that is misbehaving.

For reference, here's passwd and shadow:

root@ULCB-Linux:/etc cat passwd 
    ftp:x:11:101:ftp user:/home:/bin/false
    www:x:12:102:www user:/home:/bin/false
    sshd:x:13:100:SSH Server:/var/run/sshd:/bin/false
    service:x:500:100:Service User:/home:/bin/sh

root@ULCB-Linux:/etc cat shadow
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Are you sure the root account actually doesn't have a password? The other computers could be set up with public/private key authentication to bypass manually entering the password. – Rain May 1 '13 at 20:23
having no password is not the same as having a blank password. I'd say check the /etc/password file and make sure it has no password (i think it's just a star in the password field) -- stay logged in while testing obviously in case you bork the file format. – Sirex May 1 '13 at 20:24
SSH must always have some kind of authorization. You can however by-pass if you install a certificate witch you can generate with ssh-keygen (Linux) ou puttygen (windows) – cfreire May 1 '13 at 20:37
I amended the original with more information. Does this help anyone? – musasabi May 1 '13 at 21:06
@Sirex A * in the password field isn't "no password"; it's an old-fashioned way of locking out an account. (No password will encrypt to '*', so having it in the password field results in an account which can't log in no matter what password is given.) I gather there's a newfangled method now as well, but if you see * in the password field, that's what it means. – Aaron Miller May 1 '13 at 21:11

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