How to Fix “Paramiko Server Not Found in Known_Hosts” Error

Hello Dev! Are you facing the “Paramiko Server Not Found in Known_Hosts” error while trying to connect to a remote server? Don’t worry, you’re not alone. This error occurs when the SSH client is unable to find the server in its known_hosts file. In this article, we’ll explain what causes this error and provide you with step-by-step instructions to fix it.

Understanding the “Paramiko Server Not Found in Known_Hosts” Error

SSH (Secure Shell) is a network protocol used to securely connect to a remote server. When you connect to a server for the first time, SSH saves the server’s public key in a file called known_hosts. On subsequent connections, SSH verifies the server’s identity by checking its public key against the known_hosts file.

If the server’s public key has changed since the last time you connected, SSH will throw the “Paramiko Server Not Found in Known_Hosts” error. This is a security feature of SSH to prevent man-in-the-middle attacks.

Fixing the “Paramiko Server Not Found in Known_Hosts” Error

Step 1: Identify the Host Key

To fix the “Paramiko Server Not Found in Known_Hosts” error, you first need to identify the host key of the remote server. You can do this by running the following command in your terminal:

Command:	ssh-keygen -F <hostname>
Description:	Displays the host key of the specified hostname.

Replace <hostname> with the hostname or IP address of the remote server.

If the host key is not found, you will see the following output:

ssh-keygen: <hostname> not found in /home/user/.ssh/known_hosts

This means that you have not connected to the server before and need to add its host key to known_hosts.

Step 2: Add the Host Key to Known_Hosts

If the host key is not found in known_hosts, you can add it manually by running the following command:

Command:	ssh-keyscan <hostname> >> ~/.ssh/known_hosts
Description:	Adds the host key of the specified hostname to known_hosts.

Replace <hostname> with the hostname or IP address of the remote server.

If the host key has changed since the last time you connected, you will see a warning message similar to the following:

@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @

This means that the server’s public key has changed and you need to remove the old key from known_hosts before adding the new one.

Step 3: Remove the Old Host Key

To remove the old host key from known_hosts, run the following command:

Command:	ssh-keygen -R <hostname>
Description:	Removes the host key of the specified hostname from known_hosts.

Replace <hostname> with the hostname or IP address of the remote server.

Step 4: Connect to the Remote Server

You should now be able to connect to the remote server without seeing the “Paramiko Server Not Found in Known_Hosts” error. To connect, run the following command:

Command:	ssh <user>@<hostname>
Description:	Connects to the remote server using SSH.

Replace <user> with your username on the remote server and <hostname> with the hostname or IP address of the remote server.

Frequently Asked Questions

What is the known_hosts file?

The known_hosts file is a file in the SSH directory that stores the public keys of remote servers.

What is a man-in-the-middle attack?

A man-in-the-middle attack is an attack where a third party intercepts communication between two parties and can eavesdrop, manipulate, or steal data.

Can I automate the process of adding host keys to known_hosts?

Yes, you can use tools like Ansible or Puppet to automate the process of adding host keys to known_hosts.

What should I do if the host key has changed and I didn’t expect it to?

If the host key has changed and you didn’t expect it to, it could be a sign of a man-in-the-middle attack. In this case, you should contact the server administrator to verify the host key and take appropriate security measures.

What other SSH errors should I be aware of?

Some other common SSH errors include “Permission Denied (publickey)”, “Connection Refused”, and “Connection Timed Out”.

Conclusion

In conclusion, the “Paramiko Server Not Found in Known_Hosts” error is a common SSH error that can be fixed by adding the server’s host key to known_hosts. This error is a security feature of SSH and prevents man-in-the-middle attacks. By following the steps outlined in this article, you should be able to fix this error and connect to your remote server without any issues.