I have a CentOS Linux server with a SSH connection. It works perfectly but from time to time, the server refuses the connection.

If I reboot the server, I can SSH again.

What could be wrong?

  • 2
    What do you have in the logs?
    – Mat
    Nov 25, 2012 at 10:29
  • what log should I check?
    – Duck
    Nov 25, 2012 at 10:35
  • 1
    /var/log/messages and the other stuff in there.
    – Mat
    Nov 25, 2012 at 10:54

2 Answers 2


Try running sshd on the server in debug mode (-d, you can go up to -ddd) to get additional info. You can do this even remotely if don't happen to have the server under your table: log in, and then you can start another sshd instance on a different port with the -p option and try to log on into this instance.


Check to log on the server:

grep -Ri ssh /var/log/*

and also use SSH with more verbosity on the client:

ssh -vvv user@server

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