Set up SSH tunneling for a VPS

ssh tunneling
ssh keys
bastion host
vps
scp
Last reviewed

July 1, 2025

Last modified

July 3, 2025

This guide explains how to set up a secure, single-step SSH connection to a Virtual Private Server (VPS) at TU Delft using SSH tunneling. By default, connecting to a VPS requires first accessing a Bastion Host (an intermediary server controlling access), making it a two-step process. Therefore, it is a two-step process: to reach a remote host, a user has to connect first to the bastion host and from there to the VPS. However, by using SSH tunneling and SSH keys, you can connect to your VPS and other remote hosts in a single step.

With the method described below, you will be able to connect directly from your local machine to your VPS, bypassing the need to log in to the bastion host separately. This setup also simplifies secure file transfers between your local machine and the VPS.

Accessing a VPS

Depending on your geogaphic location, access to a VPS via SSH may be blocked by the TU Delft firewall. In such cases, you must use a VPN connection via eduVPN. Access if usally blocked if you are connecting from your home network.

Prerequisites

Before starting, you need:

  • A TU Delft NetID.
  • Access to a VPS provided by TU Delft ICT, including a username and password.
  • An SSH client installed on your local machine (usually included with most Linux and macOS distributions; for Windows, you can use a third-party SSH client like PuTTY).
  • ALinux or macOS terminal

Steps for Linux and macOS

Summary of steps
  1. Create SSH keys.
  2. Copy SSH keys to bastion host and remote server.
  3. Create a new host for SSH connection.
  4. Test connection

Set up SSH tunneling for a host (Linux Terminal)

  1. If you do not have an SSH key-pair, create one on the local machine. Go to the terminal and enter the following command. Replace <my-keyname> with a name of your choice for the SSH key, e.g., id_rsa or id_ed25519.
$  ssh-keygen -t ed25519 -f ~/.ssh/<my-keyname>

You will be promted to crate a passphrase. We recommend you to add one to make the connection more secure. The passphrase will be asked every time you connect to the VPS. To skip the passphrase, press Enter when prompted. You should see something like this:

Generating public/private ed25519 key pair.
Enter passphrase for "ed25519" (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in ~/.ssh/<my-keyname>
Your public key has been saved in ~/.ssh/<my-keyname>.pub
The key fingerprint is:
SHA256:6j06srvun06gJ5UCmD+MVq6RsPuytCO5mF4hTELnWTg root@local-machine
The key's randomart image is:
+--[ED25519 256]--+
| . ...           |
|o.oEo            |
|*. +.            |
|=*+  .           |
|o*=o+   S        |
|..+=.. .         |
|.+o.. o          |
|*+oo.o.o.        |
|B*oo*B*o..       |
+----[SHA256]-----+

A private and public key will be added to ~/.ssh.

The public key is the file with the .pub extension, e.g., <my-keyname>.pub

Tip

Similar to passwords, it is advised to rotate your SSH keys regularly (e.g., every 6 months). You can do this by generating a new key pair and replacing the old one on your local machine and VPS.

  1. Log in to your VPS and, copy the content of your public key into the VPS ~/.ssh/authorized_keys file. You can achieve this by copying the content of the public key file to the clipboard and pasting it into the authorized_keys file on the VPS. Be mindful and not remove anything from this file, or other SSH connections might stop working. Finally, save the file.

  2. Create a new host for SSH connection. On your local machine, edit the ~/.ssh/config file and add the following configuration. If the file does not exist, create it.

Host <host-nickname>
    HostName <target-host>
    User <target-username>
    ProxyJump <target-username>@linux-bastion-ex.tudelft.nl
    IdentityFile ~/.ssh/<my-keyname>

Replace: : a name of your choice for the target host, e.g., my-server : the actual name of the target host (FQDM), e.g, server.tudelft.nl : the username used to log in to the target host, usually your NetID : the username used to log in to the bastion server : the name of the SSH private key you created, e.g., id_rsa. If your private key is stored in a different location, replace the path accordingly.

  1. Test the SSH tunneling connection. Connect to the VPS using SSH tunneling by typing the command below. Use your bastion-password when asked. This is usually the password associated with your NetID.
$ ssh <host-nickname>

If you encounter problems with the connection, use the debug mode ssh -vvv <host-nickname> to find out what might have gone wrong. This command will provide detailed information about the connection process and can help you troubleshoot any issues.