F17 (fresh) - I cannot SSH

[John5342]

On Sun, May 6, 2012 at 8:30 AM, antonio <antonio.montagnani at gmail.com> wrote:
> Guido Grazioli ha scritto / said the following    il giorno/on 06/05/2012
>> Open your $HOME/.ssh/known_hosts and delete the line corrisponding
>> to the new server ip address. (you can find the line number in the
>> error message you get when trying to connect with ssh)
>>
>>
> Guido, tnx a lot..it worked!!!! can you explain why this deletion is
> necessary?? a bug??

The host key is generated when sshd is first run on a new
installation. Since you did a fresh install a new key was generated.
This new key will obviously be different to the old one you have
listed for that machine on the client in ~/.ssh/known_hosts. Therefore
it quite rightly complained that the key had changed and refused to
connect. Normally a key change could mean a man-in-the-middle attack
or similar but in this case it is a genuine and expected change.

The deletion was necessary because the host key on your newly
installed machine had changed. It's not a bug because the official way
to delete the entry is "ssh-keygen -R hostname" where hostname is the
host you want to remove the entry for. It's just often easier to
delete it by hand.

-- 
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and those who don't...