[CentOS] SSH suddenly started failing :(

Paul Heinlein heinlein at madboa.com
Thu Jun 7 20:51:50 UTC 2007

On Thu, 7 Jun 2007, John Lagrue wrote:

> I am running a VNC onto the server, and using a window in there can 
> switch users quite happily. But nobody can ssh into the server.
> My only thought is that a few days ago I changed the hostname using 
> system-network-config but I am pretty certain that I could still ssh 
> in after doing that. It just stopped working this morning.
> I've even tried rebooting in case there were odd processes hanging 
> about, but that's made no difference. At the moment I'm totally 
> stuck!

Try a different tack. Get a root shell on the machine in question and 
fire up sshd in no-fork mode under strace:

   strace -o /tmp/ssh.trace sshd -D -p 2222

Then try to ssh into that machine on port 2222 (or whatever you 
choose). Assuming it fails, close down the temporary sshd and point 
$PAGER at /tmp/ssh.trace. The failure point will likely be about 90% 
of the way through the file. (The end of the file will be related to 
closing down sshd).

Paul Heinlein <> heinlein at madboa.com <> http://www.madboa.com/

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