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Jenkins Host key verification failed

25 September 2026 · 9 min read

Jenkins Host key verification failed

Encountering the dreaded “Jenkins Host key verification failed” error can halt your continuous integration and continuous delivery (CI/CD) pipeline in its tracks. This error, often cryptic and frustrating, arises when Jenkins, your automation server, can’t securely verify the identity of a remote host, typically a server or virtual machine you’re trying to connect to for deployments or testing. It’s a security measure designed to prevent man-in-the-middle attacks, ensuring that you’re indeed communicating with the intended server and not a malicious imposter. However, when legitimate connections fail due to this verification, understanding the root cause and implementing the correct solution is crucial for maintaining a smooth and secure development workflow. This article delves into the common causes of this error and provides practical solutions to resolve it, ensuring your Jenkins jobs run without interruption. We’ll explore everything from SSH key management to host file configurations, providing you with the knowledge to troubleshoot and fix this persistent problem.

Understanding the “Jenkins Host Key Verification Failed” Error

The “Jenkins Host key verification failed” error essentially means that Jenkins is unable to trust the SSH key presented by the remote host it’s trying to connect to. This distrust can stem from several reasons. The most common is that the host key has changed since Jenkins last connected to that host. This can happen when a server is re-imaged, its SSH server is reconfigured, or when you’re connecting to a new server for the first time. Jenkins stores known host keys in a file (usually in the Jenkins user’s home directory), and if the key presented by the remote host doesn’t match what’s stored, the verification fails.

Another reason could be related to network issues or DNS resolution problems. If Jenkins can’t properly resolve the hostname of the remote server or if there’s a network interruption during the key exchange, the verification process can fail. Misconfigured SSH settings on either the Jenkins server or the remote host can also lead to this error. For example, if the remote host is using an outdated or unsupported SSH protocol, Jenkins might be unable to establish a secure connection. It’s also worth noting that incorrect user permissions or file ownership on the Jenkins server can prevent it from accessing the necessary SSH keys, triggering the verification failure. Understanding these potential causes is the first step towards effectively troubleshooting and resolving the issue.

For example, imagine a scenario where you’ve just migrated your application to a new server. During the server setup, a new SSH key pair was generated. Now, when Jenkins attempts to deploy the application to this new server, it encounters the “Jenkins Host key verification failed” error because the SSH key stored in Jenkins’ known_hosts file doesn’t match the new server’s key. This highlights the importance of updating Jenkins’ known_hosts file whenever a server’s SSH key changes.

Common Causes and Solutions

Several factors can contribute to the “Jenkins Host key verification failed” error. Let’s explore the most frequent culprits and their corresponding solutions:

  • Changed Host Key: As mentioned earlier, this is the most common cause. A server re-image, SSH server reconfiguration, or connecting to a new server can all lead to a changed host key.
  • Incorrect SSH Configuration: Misconfigured SSH settings on either the Jenkins server or the remote host can cause issues. This includes outdated SSH protocols, incorrect ciphers, or restrictive access controls.
  • Network Connectivity Problems: Intermittent network issues or DNS resolution failures can disrupt the SSH key exchange process, leading to verification failures.
  • Permissions Issues: Incorrect file permissions or ownership on the Jenkins server can prevent access to the SSH keys.

To address these common causes, consider the following solutions:

  1. Update Jenkins’ known_hosts file: This involves removing the old key and adding the new key. You can do this manually by editing the file or automatically by using the ssh-keyscan command.
  2. Disable Host Key Verification (Not Recommended for Production): While not recommended for production environments due to security risks, you can temporarily disable host key verification for testing purposes. This should be done with caution and only when you fully understand the risks involved.
  3. Verify SSH Configuration: Ensure that both the Jenkins server and the remote host are using compatible SSH protocols and ciphers. Check for any restrictive access controls that might be blocking the connection.
  4. Troubleshoot Network Connectivity: Test the network connection between the Jenkins server and the remote host. Verify DNS resolution and ensure there are no firewalls or network devices blocking the SSH traffic.
  5. Correct Permissions: Ensure that the Jenkins user has the necessary permissions to access the SSH keys and the known_hosts file.

Featured Snippet: The “Jenkins Host key verification failed” error usually occurs because Jenkins stores a known copy of a server’s SSH host key. When the server’s key changes (due to re-imaging or reconfiguration), Jenkins detects a mismatch and refuses to connect. The most common solution is to update Jenkins’ known_hosts file with the new key, ensuring that Jenkins trusts the server’s identity. This can be achieved manually or with the ssh-keyscan command.

Step-by-Step Guide to Resolving the Error

Here’s a detailed guide to resolving the “Jenkins Host key verification failed” error, focusing on updating the known_hosts file:

  1. Identify the Affected Host: Determine the hostname or IP address of the server causing the error. The Jenkins console output will typically provide this information.
  2. Access the Jenkins Server: Log in to the Jenkins server as the Jenkins user. This is crucial because the known_hosts file is specific to the Jenkins user.
  3. Remove the Old Key: Use the ssh-keygen command to remove the old key from the known_hosts file. The command is typically: ssh-keygen -R hostname, replacing “hostname” with the actual hostname or IP address.
  4. Add the New Key: Use the ssh-keyscan command to retrieve the new key and add it to the known_hosts file. The command is typically: ssh-keyscan hostname >> ~/.ssh/known_hosts, again replacing “hostname” with the actual hostname or IP address.
  5. Verify the Connection: Test the connection from the Jenkins server to the remote host using the ssh command. This will confirm that the key verification is successful.
  6. Restart Jenkins Job: Retry the Jenkins job that was failing. The updated known_hosts file should now allow Jenkins to connect to the remote host without the verification error.

Alternatively, you can manually edit the known_hosts file located in the Jenkins user’s .ssh directory. However, using the ssh-keygen and ssh-keyscan commands is generally preferred as it’s more secure and less prone to errors. Ensure the Jenkins user has the correct permissions to read and write to the .ssh directory and the known_hosts file. Proper user management and access control are essential for maintaining a secure Jenkins environment. For more information on secure Jenkins practices, refer to the official Jenkins documentation here.

Advanced Troubleshooting and Prevention

Beyond the basic solutions, here are some advanced troubleshooting techniques and preventative measures:

  • Use SSH Agent Forwarding: SSH agent forwarding allows you to use your local SSH keys on the Jenkins server without storing them directly on the server. This enhances security and simplifies key management.
  • Implement Configuration Management: Tools like Ansible, Chef, or Puppet can automate the management of SSH keys across your infrastructure, ensuring consistency and preventing key mismatches.
  • Monitor SSH Key Changes: Implement monitoring to detect changes in SSH keys on your servers. This allows you to proactively update Jenkins’ known_hosts file before connection issues arise.

Consider using a dedicated SSH key management system. Several commercial and open-source solutions can help you manage and distribute SSH keys across your infrastructure. These systems provide features like key rotation, access control, and auditing, which can significantly improve your overall security posture. Regularly auditing your SSH keys and access policies is crucial for identifying and mitigating potential security risks. Tools like Teleport Teleport can assist to discover existing SSH keys and then manage them in one place.

For example, let’s say you’re using Ansible for configuration management. You can create an Ansible playbook that automatically updates the known_hosts file on the Jenkins server whenever an SSH key changes on any of your managed servers. This ensures that Jenkins always has the correct SSH keys, preventing the “Jenkins Host key verification failed” error. This proactive approach minimizes downtime and ensures a smooth CI/CD pipeline. It is important to ensure that the Ansible user has the correct permissions on the Jenkins server. You can check the Ansible documentation here for more details.

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FAQ: Jenkins Host Key Verification Failed -----------------------------------------
Why am I getting the "Jenkins Host key verification failed" error?
This error occurs when Jenkins can't verify the SSH key of the remote host it's trying to connect to. This usually happens because the host key has changed or is not present in Jenkins' known\_hosts file.
How do I find the known\_hosts file?
The known\_hosts file is typically located in the .ssh directory within the Jenkins user's home directory (e.g., /var/jenkins\_home/.ssh/known\_hosts).
Is it safe to disable host key verification?
Disabling host key verification is generally not recommended for production environments as it compromises security. It should only be used temporarily for testing purposes and with extreme caution.
Can network issues cause this error?
Yes, intermittent network connectivity problems or DNS resolution failures can disrupt the SSH key exchange process, leading to verification failures. Ensure that the Jenkins server and remote host can communicate reliably.
What if I'm using a different SSH port?
If you're using a non-standard SSH port, you need to specify the port when using the ssh-keyscan command: ssh-keyscan -p \[port\_number\] hostname >> ~/.ssh/known\_hosts
The "**Jenkins Host key verification failed**" error, while initially daunting, is usually a straightforward issue to resolve once you understand its underlying causes. By systematically addressing the potential problems, such as outdated SSH keys, misconfigured SSH settings, or network connectivity issues, you can quickly restore your Jenkins pipeline to its optimal state. Remember, prioritizing security best practices and implementing proactive monitoring will help prevent this error from recurring and ensure a more robust and reliable CI/CD environment. Don't let this minor hurdle derail your progress. Take the steps outlined here, and you'll be back on track in no time. Explore [our other articles](https://courthousezoological.com/n7sqp6kh?key=e6dd02bc5dbf461b97a9da08df84d31c) on DevOps best practices for more tips and tricks! **Question & Answer :** I have a problem with **jenkins**, setting "git", shows the following error: 
Failed to connect to repository : Command "git ls-remote -h https://<a class="__cf_email__" data-cfemail="5c2c392e2f33321c3e35283e293f37392872332e3b" href="/cdn-cgi/l/email-protection">[email protected]</a>/person/projectmarket.git HEAD" returned status code 128: stdout: stderr: fatal: Authentication failed

I have tested with ssh:

<a class="__cf_email__" data-cfemail="5c3b35281c3e35283e293f37392872332e3b" href="/cdn-cgi/l/email-protection">[email protected]</a>:person/projectmarket.git

This is error:

Failed to connect to repository : Command "git ls-remote -h <a class="__cf_email__" data-cfemail="4d2a24390d2f24392f382e26283963223f2a" href="/cdn-cgi/l/email-protection">[email protected]</a>:person/projectmarket.git HEAD" returned status code 128: stdout: stderr: Host key verification failed. fatal: The remote end hung up unexpectedly

I’ve also done these steps with “SSH key”.

Login under Jenkins

sudo su jenkins

Copy your github key to Jenkins .ssh folder

cp ~/.ssh/id_rsa_github* /var/lib/jenkins/.ssh/

Rename the keys

mv id_rsa_github id_rsa mv id_rsa_github.pub id_rsa.pub

but still not working git repository in jenkins.

Change to the jenkins user and run the command manually:

git ls-remote -h <a class="__cf_email__" data-cfemail="42252b3602202b362037212927366c2d3025" href="/cdn-cgi/l/email-protection">[email protected]</a>:person/projectmarket.git HEAD

You will get the standard SSH warning when first connecting to a new host via SSH:

The authenticity of host 'bitbucket.org (207.223.240.181)' can't be established. RSA key fingerprint is 97:8c:1b:f2:6f:14:6b:5c:3b:ec:aa:46:46:74:7c:40. Are you sure you want to continue connecting (yes/no)?

Type yes and press Enter. The host key for bitbucket.org will now be added to the ~/.ssh/known_hosts file and you won’t get this error in Jenkins anymore.