Jenkins SSH Remote Hosts Can’t Connect to Server

Greetings, Dev! If you’re reading this article, chances are that you’ve encountered an issue with Jenkins SSH Remote Hosts not connecting to your server. Not to worry, we’ve got you covered! In this article, we will go through the possible reasons for this issue and how to troubleshoot and fix it. So, let’s get started!

What is Jenkins SSH Remote Hosts?

Jenkins SSH Remote Hosts plugin allows you to connect to remote hosts via SSH and execute shell commands. This plugin is useful when you need to execute some tasks on a remote server, such as deploying code or running tests. However, sometimes this plugin may not work as expected, and you may encounter errors like “Failed to connect to remote host” or “Connection refused”. Let’s find out why this happens and how to fix it.

Reasons for Jenkins SSH Remote Hosts Connection Issue

Firewall

One common reason for SSH connection issues is a firewall. The firewall can block incoming and outgoing SSH traffic, which will prevent Jenkins from connecting to the remote host. To fix this issue, you need to open port 22, which is the default SSH port, on both the Jenkins server and the remote host. You can do this by configuring your firewall settings.

Authentication

Another reason for SSH connection issues is authentication. If the authentication fails, Jenkins will not be able to connect to the remote host. Make sure you are using the correct username and password or SSH key to authenticate. Also, check that the SSH key is added to the authorized_keys file on the remote host. If the authentication still fails, try enabling verbose mode to get more information about the issue.

SSH Configuration

The SSH configuration can also cause connection issues. Check the SSH configuration on both the Jenkins server and the remote host to ensure that they match. Also, check that the SSH daemon is running on the remote host. You can check this by running the command “sudo service ssh status” on the remote host.

Network Connection

A poor network connection can also cause SSH connection issues. Make sure that the remote host is reachable from the Jenkins server and that there are no network issues. You can test the network connection by pinging the remote host from the Jenkins server.

Jenkins Plugin

Sometimes the issue may be with the Jenkins SSH Remote Hosts plugin itself. Make sure that you are using the latest version of the plugin and that it is compatible with your Jenkins version. If the issue persists, try disabling and re-enabling the plugin or reinstalling it.

How to Troubleshoot Jenkins SSH Remote Hosts Connection Issue

Enable Verbose Mode

Enabling verbose mode can give you more information about the SSH connection issue. To enable verbose mode, add the “-v” option to the SSH command. For example, “ssh -v user@remotehost”.

Check Logs

Check the Jenkins logs to see if there are any errors related to the SSH connection. You can find the logs in the Jenkins home directory under the “logs” folder.

Test Connection

You can test the SSH connection from the Jenkins server by running the command “ssh user@remotehost”. This will check if SSH is working and if authentication is successful.

Use Different SSH Client

If you are having issues with the SSH client that Jenkins is using, you can try using a different SSH client. For example, you can use PuTTY on Windows or the ssh command on Linux/Mac.

Verify SSH Key

If you are using SSH key authentication, make sure that the SSH key is correct and that it is added to the authorized_keys file on the remote host. You can check this by running the command “cat ~/.ssh/authorized_keys” on the remote host.

FAQ

Q1. What is SSH?

SSH (Secure Shell) is a protocol used for secure remote login and command execution over an insecure network. It provides encryption and authentication to protect the communication between the client and the server.

Q2. How do I open port 22?

You can open port 22 by configuring your firewall settings. The exact method depends on the firewall software you are using. Consult the documentation of your firewall software for instructions on how to open a port.

Q3. What is verbose mode?

Verbose mode is a mode of operation that produces more detailed output. In the case of SSH, enabling verbose mode will display more information about the SSH connection, such as the authentication method used and the SSH key fingerprint.

Q4. How do I check the SSH configuration?

You can check the SSH configuration by examining the sshd_config file on the remote host. This file is usually located in the /etc/ssh/ directory. You can also check the SSH configuration on the Jenkins server by looking at the SSH settings in the Jenkins global configuration.

Q5. Why am I getting “Connection refused” error?

“Connection refused” error occurs when the remote host is not accepting the connection request. This can happen if the SSH daemon is not running on the remote host or if the firewall is blocking the connection.

Conclusion

There you have it, Dev! In this article, we’ve gone through the possible reasons for Jenkins SSH Remote Hosts connection issues and how to troubleshoot and fix them. Remember to always check your firewall, authentication, SSH configuration, network connection, and Jenkins plugin when you encounter this issue. With these tips, you should be able to connect to your remote host via SSH without any issues.