Solved: Proxmox Host Key Verification Failed

Proxmox VE is a popular open-source platform for virtualization that is powerful and flexible, but in some cases, users may encounter errors, such as “Host key verification failed,” when attempting to perform tasks such as SSH access, adding nodes to a cluster, or programmatically managing Proxmox services. In this article, we will provide you with the reasons for this error and how to solve it.

Causes of Proxmox Host Key Verification Failed

1. The remote Server’s SSH key changed

This issue may occur after a reinstallation or reconfiguration of SSH.

2. You are previously to a different server at the same IP or hostname

Especially common in labs, home labs, or cloud environments with dynamic IPs.

3. A MITM attack is suspected

While rare in local or lab setups, this error is there for a reason – it protects you from malicious tampering.

How to Solve Host Key Verification Failed

The following parts will provide you three methods to solve host key verification failed.

Method 1. Manually Remove the Old Key

1. Open a terminal on the machine that’s failing to connect.

2. Use the following command to remove the offending key:

3. Try to connect again:

Then, you will be prompted to trust the new key. Verify it and accept.

Method 2. Edit known_hosts Directly

1. Open ~/.ssh/known_hosts in a text editor:

2. Find the line corresponding to the problematic host and delete it.

3. Save and exit, then reconnect.

Method 3. Disable Strict Host Key Checking

If you are scripting or troubleshooting and need a quick fix, use the following command:

⚠️But you should notice that this disables SSH’s host verification, exposing you to security risks. Use only in trusted environments.

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Data security for personal and enterprises is quite important, so you can use a backup tool to protect data. Here is a recommendation for AOMEI Cyber Backup, it can provide you with VM backup (VMware and Hyper-V), physical backup, file backup, and so on. While you use it, you can enjoy:

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Conclusion

Host Key Failure can be annoying, but it protects the system from intrusion when it works. That's why resolving the failure is necessary, and with the methods provided in this article, you can fix the issue in time.