SSH Connection Refused: Troubleshooting Guide
Are you experiencing an "SSH connection refused" error even though you can ping the remote server, and you can log in to the remote server locally? This article will provide a detailed guide on how to troubleshoot this issue. We will cover the key concepts, provide subtitles using H2, H3, etc., and use paragraphs and code blocks as needed. The content inside code blocks will be properly formatted according to the programming language, including indentation and tabulation where needed.
Overview
The SSH (Secure Shell) protocol is a widely-used network protocol that allows for secure remote login from one computer to another. When attempting to connect to a remote server using SSH, you may encounter an error message that reads "connection refused." This error typically means that the remote server is not allowing incoming SSH connections.
Checking Basic Connectivity
The first step in troubleshooting this issue is to check if you can reach the remote server and if SSH is running on the remote server. You can ping the remote server to check if it's reachable, and you can also check if SSH is running on the remote server using the following command:
sudo systemctl status sshIf SSH is running, the output of the above command should indicate that the service is active (running). If it's not running, start the service using the following command:
sudo systemctl start sshChecking Local SSH Connections
If you are able to log in to the remote server locally using SSH, this means that SSH is working correctly on the remote server, and the issue may be related to remote connections. To test this, try connecting to the remote server using its localhost:
ssh localhostIf the connection is successful, this confirms that SSH is working correctly on the remote server. However, if the connection is still refused, this may indicate a problem with the SSH daemon or the SSH configuration file (/etc/ssh/sshd\_config).
Checking SSH Configuration
The SSH configuration file contains settings that control how SSH behaves. To check if there are any issues with the configuration file, run the following command:
sudo nano /etc/ssh/sshd\_configCheck the following settings in the configuration file:
- Port: Ensure that the SSH port number is correct and is not blocked by a firewall.
- ListenAddress: Ensure that it's set to 0.0.0.0 or the IP address of the remote server.
- PermitRootLogin: Ensure that it's set to yes or no, depending on your requirement.
- PasswordAuthentication: Ensure that it's set to yes or no, depending on your requirement.
- AllowUsers: Ensure that the user you're trying to connect with is allowed in the configuration file.
If any of these settings are incorrect, update them and restart the SSH service.
Firewall Configuration
If the SSH configuration file is correct, the issue may be related to the firewall. By default, most Linux distributions come with a firewall enabled. To check if the SSH port is open, run the following command:
sudo ufw statusIf the SSH port is not open, you can allow incoming SSH connections by running the following command:
sudo ufw allow 22Replace 22 with the SSH port number if it's different.
Checking for SELinux Configuration
If you are using a Linux distribution that has SELinux enabled, check if SELinux is blocking SSH connections. To check the status of SELinux, run the following command:
sestatusIf SELinux is enforcing, check the SSH configuration using the following command:
sestatus | grep sshIf the output of the above command is empty, SELinux is not allowing SSH connections. To allow SSH connections, run the following command:
sudo semanage port -a -t ssh\_port
```bash
-p tcp 22
```
In this article, we have covered several steps that can help you troubleshoot an "SSH connection refused" error. The key concepts covered include checking basic connectivity, checking local SSH connections, checking SSH configuration, firewall configuration, and SELinux configuration. By following these steps, you should be able to identify and resolve the issue.
References
- SSH Configuration File: https://man.openbsd.org/sshd_config
- SELinux: https://wiki.centos.org/HowTos/SELinux
- SUSE Firewall: https://documentation.suse.com/sles/15-SP3/html/SLES-all/art-sle-firewall.html
- Ubuntu Firewall: https://help.ubuntu.com/community/UFW