How to Set Up a VPN Server on Linux

A VPN (Virtual Private Network) provides a secure, encrypted connection between your devices and the internet. By setting up your own VPN server with OpenVPN, you can ensure privacy, bypass content restrictions, and protect your data from unauthorized access. This guide will walk you through the process of setting up an OpenVPN server on your Linux system.

Using OpenVPN

Step 1: Open Terminal

Open the terminal by pressing Ctrl + Alt + T on your keyboard or by searching for it in the applications menu.

Step 2: Install OpenVPN and Easy-RSA

On Debian/Ubuntu-based systems:

sudo apt update && sudo apt install openvpn easy-rsa

On Fedora/RPM-based systems:

sudo dnf update && sudo dnf install openvpn easy-rsa

Step 3: Set Up Certificate Authority (CA)

A Certificate Authority (CA) is necessary to generate and sign certificates for your VPN server and clients. To set up a CA, follow these steps:

Create a directory for your CA:

mkdir -p ~/easy-rsa && cp -r /usr/share/easy-rsa/* ~/easy-rsa/

Edit the vars file to customize your CA:

nano ~/easy-rsa/vars

Modify the following lines to match your organization’s information:

export KEY_COUNTRY=”US”
export KEY_PROVINCE=”CA”
export KEY_CITY=”SanFrancisco”
export KEY_ORG=”YourOrganization”
export KEY_EMAIL=”you@example.com”
export KEY_OU=”MyOrganizationalUnit”

Save the file and exit the text editor.

Initialize the CA and generate the necessary files:

cd ~/easy-rsa && source ./vars && ./clean-all && ./build-ca

Step 4: Create Server Certificate and Key

To create the server certificate and key, execute the following command:

./build-key-server server

When prompted, confirm that you want to sign the certificate and commit the changes.

Step 5: Generate Diffie-Hellman Parameters

Diffie-Hellman parameters are used to establish a secure connection between the server and clients. Generate the parameters with this command:

./build-dh

Step 6: Configure OpenVPN Server

Copy the necessary files to the OpenVPN directory:

sudo cp ~/easy-rsa/keys/{ca.crt,server.crt,server.key,dh.pem} /etc/openvpn/

Create a new OpenVPN server configuration file:

sudo nano /etc/openvpn/server.conf

This example uses nano. You can use the text editor of your choice.

Add the following lines to the file:

port 1194
proto udp
dev tun
ca ca.crt
cert server.crt
key server.key
dh dh.pem
server 10.8.0.0 255.255.255.0
push “redirect-gateway def1 bypass-dhcp”
push “dhcp-option DNS 208.67.222.222”
push “dhcp-option DNS 208.67.220.220”
keepalive 10 120
cipher AES-256-CBC
user nobody
group nogroup
persist-key
persist-tun
status openvpn-status.log
verb 3

Save the file and exit the text editor.

Step 7: Enable IP Forwarding

To allow VPN traffic to be forwarded between the server and clients, enable IP forwarding:

sudo nano /etc/sysctl.conf

Uncomment or add the following line:

net.ipv4.ip_forward = 1

Save the file and exit the text editor. Apply the changes with the following command:

sudo sysctl -p

Step 8: Configure Firewall Rules

Adjust your firewall settings to allow VPN traffic and enable NAT for IP forwarding:

On Debian/Ubuntu-based systems:

sudo ufw allow 1194/udp && sudo nano /etc/ufw/before.rules

Add the following lines at the beginning of the file:

*nat
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -s 10.8.0.0/8 -o eth0 -j MASQUERADE
COMMIT

Replace eth0 with the name of your network interface, if necessary. Save the file and exit the text editor.

On Fedora/RPM-based systems:

sudo firewall-cmd –add-service=openvpn && sudo firewall-cmd –add-masquerade && sudo firewall-cmd –permanent –add-service=openvpn && sudo firewall-cmd –permanent –add-masquerade

Step 9: Start and Enable OpenVPN Service

Start and enable the OpenVPN service:

sudo systemctl start openvpn@server && sudo systemctl enable openvpn@server

Step 10: Create Client Certificates and Configuration Files

For each client that will connect to your VPN server, create a client certificate and configuration file:

Generate a client certificate:

cd ~/easy-rsa && ./build-key client1

Replace client1 with a unique name for each client.

Create a client configuration file:

sudo mkdir -p /etc/openvpn/client-configs && sudo nano /etc/openvpn/client-configs/client1.ovpn

Add the following lines to the file:

client
dev tun
proto udp
remote YourServerPublicIP 1194
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
cipher AES-256-CBC
verb 3
<ca>

Copy the contents of ca.crt from ~/easy-rsa/keys/ca.crt and paste it after the <ca> line. Add the following lines:

</ca>
<cert>

Copy the contents of client1.crt from ~/easy-rsa/keys/client1.crt and paste it after the <cert> line.

Add the following lines:

</cert>
<key>

Copy the contents of client1.key from ~/easy-rsa/keys/client1.key and paste it after the <key> line.

Add the following line:

</key>

Save the file and exit the text editor.

Step 11: Distribute Client Configuration Files

Distribute the client configuration files to your clients. They can use these files to connect to the VPN server using an OpenVPN client application.

Conclusion

You have now successfully set up an OpenVPN server on your Linux system. By following this guide, you can provide secure, encrypted connections for your devices and protect your data from unauthorized access.