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Ethan Bertrand
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Asked: 2022-05-12T12:16:27+00:00 In:

Steps to fix the error “ the authenticity of host can’t be established”

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I get the “the authenticity of host can’t be established” issue when trying to ssh to a machine. Here is the detail of the error I got the error message:

The authenticity of host '<host>' can't be established.
 ECDSA key fingerprint is SHA256:TER0dEslggzS/BROmiE/s70WqcYy6bk52fs+MLTIptM.
 Are you sure you want to continue connecting (yes/no)? yes
 Warning: Permanently added 'pc' (ECDSA) to the list of known hosts.

Please give me some advice to solve this problem.

the authenticity of host
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2 Answers

  1. Best Answer
    Expert

    The cause: I think this error occurs if you frequently edit keys, this warning will appear owing to security features; do not disable this feature. This warning only appeared once. If the problem persists after a second connection, the issue is most likely with writing to the known_hosts file. After that, you’ll receive the following message:

    Failed to add the host to the list of known hosts

    The solution: To solve this problem you can change the file’s owner or make it writable by your user by fixing the file’s permissions.

    sudo chown -v $USER ~/.ssh/known_hosts
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  2. An old question that deserves a better response.

    Without disabling StrictHostKeyChecking, you can disable interactive prompt (which is insecure).

    The following logic can be incorporated into your script:

    if [ -z "$(ssh-keygen -F $IP)" ]; then
 ssh-keyscan -H $IP >> ~/.ssh/known_hosts
fi

    It checks to see if the public key for the server is in known_hosts. It checks if the public key of the server is in known_hosts. If it is not, it requests it from the server and adds that to known_hosts.

    This means that you will be exposed to Man-In the-Middle attack once only.

    • Make sure that the script connects over a secure channel.
    • Inspecting logs and known_hosts to manually check fingerprints (to be done once only)
    • 22

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