Set Up Your Own WireGuard VPN Server on Debian

This tutorial is going to show you how to set up your own WireGuard VPN server on Debian. WireGuard is made specifically for the Linux kernel. It runs inside the Linux kernel and allows you to create fast, modern, and secure VPN tunnel.

Features of WireGuard VPN

  • Lightweight and super fast speed, blowing OpenVPN out of the water.
  • Cross-platform. WireGuard can run on Linux, BSD, macOS, Windows, Android, iOS, and OpenWRT.
  • User authentication is done by exchanging public keys, similar to SSH keys.
  • It assigns static tunnel IP addresses to VPN clients. Some folks may not like it, but it can be useful in some cases.
  • Mobile devices can switch between Wi-Fi and mobile network seamlessly without dropping any connectivity.
  • It aims to replace OpenVPN and IPSec in most use cases.

Prerequisites

This tutorial assumes that the VPN server and VPN client are both running Debian operating system.

Step 1: Install WireGuard on Debian Server and Desktop

Log into your Debian server. WireGuard is included in the Debian 11 (Bullseye) repository, so you can run the following commands to install it.

sudo apt update
sudo apt install wireguard wireguard-tools linux-headers-$(uname -r)

Debian 10 users need to add the backport repository with the following command.

echo "deb http://deb.debian.org/debian buster-backports main" | sudo tee /etc/apt/sources.list.d/buster-backports.list

Then install WireGuard.

sudo apt update
sudo apt -t buster-backports install wireguard wireguard-tools wireguard-dkms linux-headers-$(uname -r)

Use the same commands to install WireGuard on your local Debian computer (the VPN client). Note that you also need to install the openresolv package on the client to configure DNS server.

sudo apt install openresolv

Step 2: Generate Public/Private Keypair

Server

Run the following command on the Debian server to create a public/private key pair, which will be saved under /etc/wireguard/ directory.

wg genkey | sudo tee /etc/wireguard/server_private.key | wg pubkey | sudo tee /etc/wireguard/server_public.key

Debian-wireguard-VPN-server-generate-public-private-key

Client

Run the following command to create a public/private key pair on the local Debian computer (the VPN client).

wg genkey | sudo tee /etc/wireguard/client_private.key | wg pubkey | sudo tee /etc/wireguard/client_public.key

Step 3: Create WireGuard Configuration File

Server

Use a command-line text editor like Nano to create a WireGuard configuration file on the Debian server. wg0 will be the network interface name.

sudo nano /etc/wireguard/wg0.conf

Copy the following text and paste it to your configuration file. You need to use your own server private key and client public key.

[Interface]
Address = 10.10.10.1/24
SaveConfig = true
PrivateKey = KIWV46zRQIFUu4qrffNBB23yuaST99PLCC3zigPbsGc=
ListenPort = 51820

[Peer]
PublicKey = 75VNV7HqFh+3QIT5OHZkcjWfbjx8tc6Ck62gZJT/KRA=
AllowedIPs = 10.10.10.2/32

Debian-wireguard-VPN-server-configuration-file

Where:

  • Address: Specify the private IP address of the VPN server. Here I’m using the 10.10.10.0/24 network range. 10.10.10.1 is the private IP address for the VPN server.
  • SaveConfig: the configuration should be saved on shutdown using the current status of the interface.
  • PrivateKey: The private key of VPN server, which can be found in the /etc/wireguard/server_private.key file on the server.
  • ListenPort: WireGuard VPN server will be listening on UDP port 51820, which is the default.
  • PublicKey: The public key of VPN client, which can be found in the /etc/wireguard/client_public.key file on the client computer.
  • AllowedIPs: IP addresses the VPN client is allowed to use. In this example, the client can only use the 10.10.10.2 IP address inside the VPN tunnel.

Save and close the file. (To save a file in Nano text editor, press Ctrl+O, then press Enter to confirm. Press Ctrl+X to exit.)

Change the file permission mode so that only root user can read the files.

sudo chmod 600 /etc/wireguard/ -R

Client

Use a command-line text editor like Nano to create a WireGuard configuration file on your local Debian computer. wg-client0 will be the network interface name.

sudo nano /etc/wireguard/wg-client0.conf

Copy the following text and paste it to your configuration file. You need to use your own client private key and server public key.

[Interface]
Address = 10.10.10.2/24
DNS = 10.10.10.1
PrivateKey = cOFA+x5UvHF+a3xJ6enLatG+DoE3I5PhMgKrMKkUyXI=

[Peer]
PublicKey = kQvxOJI5Km4S1c7WXu2UZFpB8mHGuf3Gz8mmgTIF2U0=
AllowedIPs = 0.0.0.0/0
Endpoint = 12.34.56.78:51820
PersistentKeepalive = 25

Where:

  • Address: Specify the private IP address of the VPN client.
  • DNS: specify 10.10.10.1 (VPN server) as the DNS server. It will be configured via the resolvconf command.
  • PrivateKey: The client’s private key, which can be found in the /etc/wireguard/client_private.key file on the client computer.
  • PublicKey: The server’s public key, which can be found in the /etc/wireguard/server_public.key file on the server.
  • AllowedIPs: 0.0.0.0/0 represents the whole Internet, which means all traffic to the Internet should be routed via the VPN.
  • Endpoint: The public IP address and port number of VPN server. Replace 12.34.56.78 with your server’s real public IP address.
  • PersistentKeepalive: Send an authenticated empty packet to the peer every 25 seconds to keep the connection alive. If PersistentKeepalive isn’t enabled, the VPN server might not be able to ping the VPN client.

Save and close the file.

Change the file mode so that only root user can read the files.

sudo chmod 600 /etc/wireguard/ -R

Step 4: Enable IP Forwarding on the Server

In order for the VPN server to route packets between VPN clients and the Internet, we need to enable IP forwarding. Edit sysctl.conf file.

sudo nano /etc/sysctl.conf

Add the following line at the end of this file.

net.ipv4.ip_forward = 1

Save and close the file. Then apply the changes with the below command. The -p option will load sysctl settings from /etc/sysctl.conf file. This command will preserve our changes across system reboots.

sudo sysctl -p

Step 5: Configure IP Masquerading on the Server

We need to set up IP masquerading in the server firewall, so that the server becomes a virtual router for VPN clients. I will use UFW, which is a front end to the iptables firewall. Install UFW on Debian with:

sudo apt install ufw

First, you need to allow SSH traffic.

sudo ufw allow 22/tcp

Then edit /etc/default/ufw file.

sudo nano /etc/default/ufw

Change the default forward policy from “DROP” to “ACCEPT”.

DEFAULT_FORWARD_POLICY="ACCEPT"

Save and close the file. Next, find the name of your server’s main network interface.

ip addr

As you can see, it’s named ens3 on my Debian server.

debian-wireguard-firewall

To configure IP masquerading, we have to add iptables command in a UFW configuration file.

sudo nano /etc/ufw/before.rules

By default, there are some rules for the filter table. Add the following lines at the end of this file. Replace ens3 with your own network interface name.

# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -o ens3 -j MASQUERADE

# End each table with the 'COMMIT' line or these rules won't be processed
COMMIT

In Nano text editor, you can go to the end of the file by pressing Ctrl+W, then pressing Ctrl+V.

UFW NAT table POSTROUTING MASQUERADE

The above lines will append (-A) a rule to the end of of POSTROUTING chain of nat table. It will link your virtual private network with the Internet. And also hide your network from the outside world. So the Internet can only see your VPN server’s IP, but can’t see your VPN client’s IP, just like your home router hides your private home network.

Save and close the file. Then enable UFW.

sudo ufw enable

If you have enabled UFW before, then you can use systemctl to restart UFW.

sudo systemctl restart ufw

Now if you list the rules in the POSTROUTING chain of the NAT table by using the following command:

sudo iptables -t nat -L POSTROUTING

You can see the Masquerade rule.

wireguard-IP-Masquerading-ufw-debian

Step 6: Install a DNS Resolver on the Server

Since we specified the VPN server as the DNS server for client, we need to run a DNS resolver on the VPN server. We can install the bind9 DNS server.

sudo apt install bind9

Once it’s installed, BIND will automatically start. You can check its status with:

systemctl status bind9

Sample output:

 named.service - BIND Domain Name Server
     Loaded: loaded (/lib/systemd/system/named.service; enabled; vendor preset: enabled)
     Active: active (running) since Sun 2020-05-17 08:11:26 UTC; 37s ago
       Docs: man:named(8)
   Main PID: 13820 (named)
      Tasks: 5 (limit: 1074)
     Memory: 14.3M
     CGroup: /system.slice/named.service
             └─13820 /usr/sbin/named -f -u bind

If it’s not running, start it with:

sudo systemctl start bind9

Edit the BIND DNS server’s configuration file.

sudo nano /etc/bind/named.conf.options

Add the following line to allow VPN clients to send recursive DNS queries.

allow-recursion { 127.0.0.1; 10.10.10.0/24; };

wireguard BIND DNS resolver

Save and close the file. Restart BIND9 for the changes to take effect.

sudo systemctl restart bind9

Then you need to run the following command to allow VPN clients to connect to port 53.

sudo ufw insert 1 allow in from 10.10.10.0/24

Step 7: Open WireGuard Port in Firewall

Run the following command to open UDP port 51820 on the server.

sudo ufw allow 51820/udp

Step 8: Start WireGuard

server

Run the following command on the server to start WireGuard.

sudo wg-quick up /etc/wireguard/wg0.conf

To stop it, run

sudo wg-quick down /etc/wireguard/wg0.conf

You can also use systemd service to start WireGuard.

sudo systemctl start [email protected]

Enable auto-start at system boot time.

sudo systemctl enable [email protected]

Check its status with the following command. Its status should be active (exited).

systemctl status [email protected]

Now WireGuard server is ready to accept client connections.

Client

Start WireGuard.

sudo systemctl start [email protected]

Enable auto-start at system boot time.

sudo systemctl enable [email protected]

Check its status:

systemctl status [email protected]

Now go to this website: http://icanhazip.com/ to check your public IP address. If everything went well, it should display your VPN server’s public IP address instead of your client computer’s public IP address.

Policy Routing

By default, all traffic on the VPN client will be routed through the VPN server. Sometimes you may want to route only a specific type of traffic, based on the transport layer protocol and the destination port. This is known as policy routing.

Policy routing is configured on the client computer, and we need to stop the WireGuard client process.

sudo systemctl stop [email protected]

Then edit the client configuration file.

sudo nano /etc/wireguard/wg-client0.conf

For example, if you add the following 3 lines in the [interface] section, then WireGuard will create a routing table named “1234” and add the ip rule into the routing table. In this example, traffic will be routed through VPN server only when TCP is used as the transport layer protocol and the destination port is 25, i.e, when the client computer sends emails.

Table = 1234
PostUp = ip rule add ipproto tcp dport 25 table 1234
PreDown = ip rule delete ipproto tcp dport 25 table 1234

wireguard-vpn-policy-routing-debian

Save and close the file. Then start WireGurad client again.

sudo systemctl start [email protected]

VPN Kill Switch

By default, your computer can access the Internet via the normal gateway when the VPN connection is disrupted. You may want to enable the kill switch feature, which prevents the flow of unencrypted packets through non-WireGuard interfaces.

Stop the WireGuard client process.

sudo systemctl stop [email protected]

Edit the client configuration file.

sudo nano /etc/wireguard/wg-client0.conf

Add the following two lines in the [interface] section.

PostUp = iptables -I OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT
PreDown = iptables -D OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT

Like this:

[Interface]
Address = 10.10.10.2/24
DNS = 10.10.10.1
PrivateKey = cOFA+x5UvHF+a3xJ6enLatG+DoE3I5PhMgKrMKkUyXI=
PostUp = iptables -I OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT
PreDown = iptables -D OUTPUT ! -o %i -m mark ! --mark $(wg show %i fwmark) -m addrtype ! --dst-type LOCAL -j REJECT

[Peer]
PublicKey = kQvxOJI5Km4S1c7WXu2UZFpB8mHGuf3Gz8mmgTIF2U0=
AllowedIPs = 0.0.0.0/0
Endpoint = 12.34.56.78:51820
PersistentKeepalive = 25

Save and close the file. Then start the WireGuard client.

sudo systemctl start [email protected]

Wrapping Up

That’s it! I hope this tutorial helped you install and configure WireGuard on Debian. As always, if you found this post useful, then subscribe to our free newsletter to get more tips and tricks 🙂

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2 Responses to “Set Up Your Own WireGuard VPN Server on Debian

  • Thanks for the lovely tutorial…
    Could you also include how to configure SPLIT TUNNELING so that you can configure certain services through VPN and rest of it through your ISP ?

    • I think the “policy routing” in this article is what you want with split tunneling by services. You just need to adjust the protocol type and destination port.

      If you need split tunneling by IP addresses like in a typical corporate environment, edit the client configuration file.

      sudo nano /etc/wireguard/wg-client0.conf

      Change

      AllowedIPs = 0.0.0.0/0

      To

      AllowedIPs = 10.10.10.0/24

      So traffice will be routed through VPN only when the destination address is in the 10.10.10.0/24 network range.
      Save and close the file. Then restart WireGuard client.

      sudo systemctl restart [email protected]

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