Introduction

In today’s digital landscape, managing servers efficiently and securely is paramount for businesses and developers alike. With the increasing reliance on cloud computing and virtualization technologies, tools like Proxmox have made it easier to deploy and manage multiple virtual machines, including Ubuntu servers.

Secure Shell (SSH) is a protocol that enables secure remote access to servers, allowing users to execute commands, manage files, and configure services from anywhere in the world. Whether you're a system administrator overseeing server health or a developer deploying applications, knowing how to connect to your server via SSH is essential.

In this blog post, we will guide you through the process of connecting to an Ubuntu server installed on Proxmox using PuTTY for terminal access and FileZilla for secure file transfers. We’ll also cover how to generate an SSH key pair using PuTTY and use it for secure authentication. By the end of this guide, you’ll be equipped with the knowledge to manage your server effectively and transfer files securely, enhancing your workflow and productivity.

Prerequisites

Before we begin, ensure you have the following:

1. Ubuntu Server Installed on Proxmox: Make sure your Ubuntu server is set up on Proxmox. If you need help with this, check out my Step-by-Step Guide to Installing Ubuntu Server on Proxmox.
2. SSH Access: You should have SSH access enabled on your server. For detailed instructions on configuring SSH on Ubuntu, refer to my blog on SSH Configurations on Ubuntu Server.
3. Client Software:

• PuTTY: A popular SSH client for Windows, which also includes PuTTYgen for generating SSH keys. Download PuTTY from official page.
• FileZilla: An FTP client that supports SFTP (SSH File Transfer Protocol). Download FileZila from official page.

Understanding Public and Private Keys

What Are Public and Private Keys?

Public and private keys are components of asymmetric encryption, a method that uses a pair of keys for secure communication. Here’s how they work:

Public Key:

• The public key is meant to be shared with anyone. It can be distributed widely without compromising security.
• It is used to encrypt data or verify a digital signature.
• In the context of SSH, the public key is added to the server's authorized_keys file, allowing the server to recognize and authenticate clients that possess the corresponding private key.

Private Key:

• The private key is kept secret and should never be shared. It is crucial for maintaining the security of your encrypted data.
• The private key is used to decrypt data that has been encrypted with the corresponding public key or to create a digital signature.
• In SSH, the private key is used to authenticate your identity when connecting to the server. The server uses the public key to verify the signature made by the private key.

How They Work Together

When you attempt to connect to an SSH server:

1. The server sends a challenge to your client.
2. Your client uses the private key to sign the challenge.
3. The server then uses the public key to verify that the signature is valid.
4. If verification is successful, you gain access without needing to enter a password.

This method enhances security because even if someone intercepts the public key, they cannot access the server without the corresponding private key.

Step 1: Generate SSH Key Pair Using PuTTY

Open PuTTYgen:

• Launch PuTTYgen, which is included with your PuTTY installation.

Select Key Type:

• In the PuTTYgen window, make sure the option for RSA is selected.
• Set the Number of bits in a generated key to 4096 for enhanced security.

Generate Key:

• Click the Generate button.
• Move your mouse around the blank area to generate randomness until the key is created.

Add a Passphrase (optional):

• You can enter a passphrase to add an extra layer of security to your private key. This is optional but recommended.

Save Keys:

• Click on the Save private key button to save your private key (e.g., mykey.ppk).

Click on the Save public key button to save your public key (e.g., mykey.pub). You can also copy the public key from the text area above.

Step 2: Add Public Key to the Ubuntu Server

Now, you need to add the public key to your Ubuntu server to allow key-based authentication.

Copy the Public Key:

• If you copied the public key in the previous step, you can paste it directly. If not, open the mykey.pub file you saved to view its contents. The key will look something like this:

> ssh-rsa AAAAB3... user@hostname

Connect to Your Server:

• Use PuTTY or another SSH client to connect to your Ubuntu server using your username and password.

Create .ssh Directory:

• Once logged in, create a .ssh directory in your home folder if it doesn’t already exist:

> mkdir -p ~/.ssh
> chmod 700 ~/.ssh

Add the Public Key:

• Open the authorized_keys file:

> nano ~/.ssh/authorized_keys

• Paste your public key into this file and save it (Ctrl + O, then Enter to save, and Ctrl + X to exit).

Set Permissions: Ensure the permissions are set correctly:

> chmod 600 ~/.ssh/authorized_keys

Step 3: Connecting with PuTTY Using Private Key

Open PuTTY:

• Launch the PuTTY application on your computer.
• Configure Connection:
• In the Host Name (or IP address) field, enter the IP address of your server.
• Ensure the Port is set to 22.
• Under Connection type, make sure SSH is selected.

Load Private Key:

• In the left sidebar, navigate to Connection > SSH > Auth.
• Click the Browse button next to the Private key file for authentication field and select your private key file (e.g., mykey.ppk).

Save Session (optional):

• In the Saved Sessions field, you can give your session a name and click Save for future use.

Click Open:

• Click the Open button to initiate the connection.

Login:

• A terminal window will appear asking for your username. Enter your username and press Enter. If you set a passphrase for your key, you will be prompted to enter it.

Successful Connection:

• If your credentials and key are correct, you’ll be logged into your Ubuntu server, and you’ll see a command prompt.

Step 4: Connecting with FileZilla

Open FileZilla:

• Launch FileZilla on your computer.

Site Manager:

• Click on the File menu and select Site Manager.
• Click on New Site and name it (e.g., My Ubuntu Server).

Configure Connection:

• Host: Enter the IP address of your server.
• Port: Set to 22.
• Protocol: Select SFTP - SSH File Transfer Protocol.
• Logon Type: Choose Key file for SSH key authentication.
• User: Enter your username.
• Key file: Browse to the location of your private SSH key (e.g., mykey.ppk).

Connect:

• Click Connect to establish a connection to your server.

File Transfer:

• Once connected, you will see your local files on the left and the server files on the right. You can drag and drop files between your local machine and the server.

Step 5: Troubleshooting Connection Issues

• Firewall Settings: Ensure that your server’s firewall allows incoming connections on port 22. You may need to adjust your ufw (Uncomplicated Firewall) settings on Ubuntu.
• SSH Service: Verify that the SSH service is running on your server. You can check this by running sudo systemctl status ssh on the server.
• Network Issues: Ensure your local network allows outgoing connections on port 22.

Conclusion

Connecting to your Ubuntu server via SSH is not just a technical skill—it’s a gateway to effective server management. By generating SSH keys using PuTTY, you enhance security while simplifying the login process. Understanding the concept of public and private keys ensures you can use this method safely and effectively.

With tools like PuTTY and FileZilla, you can efficiently navigate the server's command line and transfer files securely, whether for development, deployment, or routine maintenance.

Understanding how to establish these connections empowers you to maintain and troubleshoot your server environment with confidence. As you continue your journey in server management, these foundational skills will enable you to adapt to new challenges and technologies.

With your Ubuntu server up and running on Proxmox, and armed with the knowledge from the linked resources, you’re well-equipped to make the most of your virtualized infrastructure. Explore further, experiment, and leverage the full potential of your server environment!