I've installed Debian 4.0 onto my Sun Ultra5, choosing the Desktop Environment, Web Server, and File Server configuration. After this, I installed ssh by doing "apt-get install ssh".

My Windows XP machine can connect to it fine using PuTTY, but using ssh from a command line in Fedora Core on the same machine results in "Connection closed". I've also tried this from my Mandriva machine, and I'm still getting the same. I'm guessing it's something to do with either the protocols or the keys.

Can anyone give me a few suggestions?

Cheers,
Zomb.

Is there any type of error message besides "Connection closed"?
Try connecting with 'ssh -v' (up to three '-v' for more verbosity). Maybe that'll shed some light on it.

I've never had any problems like that with the default Debian settings. Until I change all the ports, I can use ssh from any other machine as normal. Is it possible your problem has something to do with a router? Either way, you can check your basic settings at /etc/ssh/sshd_config. If you made settings of your own, the config file will be in your /home/you/.ssh/ directory.

Thanks for the replies, peeps. My Windows XP and Fedora Core 6 installation are on the same PC, with the same IP etc. PuTTY under Windows works (using ssh 2 protocol), but ssh from a command line in Fedora doesn't. I've also tried "ssh -2 sun-z13" from the Fedora command line.

I've tried "ssh -v sun-z13" as suggested...
I know this has gotta be something simple.

Anything in /var/log/auth.log?

Why are you all suspecting something wrong with the Debian ssh server? If PuTTY can connect to it, then obviously it's working. The ssh CLIENT settings in Fedora Core and Mandriva are the obvious suspects.

My guess is that both FC and Mandriva have the ssh client configured for key based instead of password based authentication. By default, Debian's openssh-server installs with password based authentication.

Cheers, IsaacKuo. That's what I was thinking (client problem), but isn't key based authentication for when you don't want to use a password to log in? I don't want that, I just want to be able to ssh into the box just like I do to my Mandriva and Fedora boxes.

I can't believe this is a problem, such a fundamentally simple task...

Cheers,
Zomb.

Key based authentication can work either way: with a password or without. Although a lot of people do it without a pass because it's quicker, I prefer to have a password for the key since it's more secure.

Have you checked the default client settings on your other distros?

You said XP and FC share the same IP? That might be the source of the problem. Check the sshd log details.

Thanks for the reply, but I don't understand how having one of my machines dual-booted with XP and FC could be the problem. Using PuTTY under Windows on that machine works fine, but using ssh on the FC command line on the same machine results in "Connection closed". Doesn't that prove that it's a configuration problem on either the ssh server on the Debian box, or the ssh client on FC (and also on my Mandriva box)?

Cheers,
Zomb.

Is there anything at the time of the connection attempt(s) in /var/log/auth.log on the Debian server?

Depending on how you connect, the first time an IP address is seen by a sshd it keeps some information. When this information doesn't match later on, it thinks it's some kind of attack.

Just change the IP address of your Fedora installation to an IP address you haven't used to connect to sshd and try again.

I'd start by deleting the ~/.ssh/known_hosts file on the Fedora box.