Saturday, May 24, 2014

Solution for RSA Host Key verification failed

When making an SSH connection to a machine we've never contacted before, The server presented its host key to the client as part of the initial handshake.
On Client when you said 'yes', SSH client saves the server's host key locally in the file $HOME/.ssh/known_hosts. for root user location is /root/.ssh/known_hosts.This file is, effectively, your personal Certificate Authority -- it is the list of all SSH server

The next time you connect to this machine, your SSH client will go through the standard steps of verifying the remote machine and allowing you to log in, this time, it did not ask you to verify the key fingerprint at all. That's because the key was in your $HOME/.ssh/known_hosts file. The SSH client actually checks in a few places:
The global known hosts file, typically /etc/ssh/ssh_known_hosts. This can be modified by changing the GlobalKnownHostsFile parameter in the ssh configuration file (typically /etc/ssh/ssh_config).
The user's known hosts file, typically $HOME/.ssh/known_hosts. This can be modified by changing the UserKnownHostsFile parameter in the ssh configuration file.

If the operating system of the host computer changes (e.g. re-install with the same hostname), an error message will occur notifying the user that the remote host ID has changed and access will be denied:

RSA Host Key verification failed
This was actually pretty easy to fix. Since you are already trying to SSH, this assumes you already know where Terminal is and you have it opened

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