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Setting up an OpenVPN server with Ubuntu

This guide will walk you through the steps involved in setting up an OpenVPN server on an Ubuntu host that allows you to securely access your home/office network from a remote location and optionally send all of your network traffic through it so you can access the internet securely as well.

Before using this guide, we highly recommend you read through our Introduction to Running an OpenVPN Server Article.

Preparation

For this guide, we assume:

  • You have already installed the latest LTS version of Ubuntu (26.04 at time of writing)
  • You have root access to this installation
  • This installation of Ubuntu is a clean install
  • Know the name of your network interfaces (instructions just below)
  • You have access to the server via Terminal or SSH
  • You are able to copy files on and off the server using SCP or a similar protocol
  • You already have a copy of Viscosity installed on your client device

If you need to download and install a copy of Ubuntu, information can be found at https://www.ubuntu.com/download. We won't be covering the details of setting up an Ubuntu instance, many guides can be found online. If you are running a different version of Ubuntu, it's very likely that many or even all of the steps outlined in this guide will still apply. If you are looking to set up an OpenVPN server on a different operating system, please check out our other guides.

If you don't have a copy of Viscosity already installed on your client, then please check out this setup guide for installing Viscosity (Mac | Windows).

If you're new to SSH or SCP, we have some instructions in our Introduction Guide.

To get the name of your Primary Network Interface (WAN Access), run the following on your Ubuntu server:
ip route | grep default | awk '{print $5}'. You should see an interface name similar to "ens224" or "enp1s0". If you are using a different version of Ubuntu, you may need to run just ip route | grep default instead and look for the interface name in the output.

If you have a second network interface for accessing machines on your local network, you will need the name of this as well when setting up the firewall and routing.

Support

Unfortunately we cannot provide any direct support for setting up your own OpenVPN server. We provide this guide as a courtesy to help you get started with, and make the most of, your copy of Viscosity. We've thoroughly tested the steps in this guide to ensure that, if you follow the instructions detailed below, you should be well on your way to enjoying the benefits of running your own OpenVPN server.

For further information or help with Ubuntu, there are a range of community resources available at https://www.ubuntu.com/community

Getting Started

First, update your server:

sudo apt update
sudo apt -y upgrade

You may be informed that you need to restart after the package upgrades are complete. If so, go ahead and restart, then log back in and continue on.

To set up an OpenVPN server, we need to install OpenVPN from Ubuntu's package repositories:

sudo apt -y install openvpn

Generating Configurations, Certificates and Keys

The next step is to generate your configurations for the server and your clients as well as certificates to go with them. You can do this easily by following the Creating Certificates and Keys Guide. You can either follow the section for Ubuntu and copy your client configurations off the server (we recommend this), or generate everything on your PC or Mac and copy the server folder that is generated onto your Ubuntu server.

If you use the default DNS Server (10.8.0.1), you will need to set up a DNS server yourself, instructions are at the end of this article. We recommend instead using an existing DNS server, a publicly available DNS server like Google's (8.8.8.8 and 8.8.4.4) is the easiest.

Once you have generated your server and client configurations, you will need to transfer the server configuration to your server, or transfer your client configurations off your server. If you have local access, a USB drive is the easiest. If not, we have some help on how to transfer files with SCP in our Introduction Guide.

IP Forwarding

In order to forward our requests passing through the VPN, we want the OpenVPN server to act like a router. As such, we need to enable IP forwarding.

To enable IP forwarding, and ensure it remains enabled after a reboot, create a sysctl configuration file for OpenVPN:

echo "net.ipv4.ip_forward=1" | sudo tee /etc/sysctl.d/99-openvpn.conf

Now load the updated sysctl settings:

sudo sysctl --system

Firewall Rules

We will use the Uncomplicated Firewall (ufw) that is installed by default on Ubuntu to control how traffic is passed through the OpenVPN server. If your Ubuntu server is externally accessible (has a direct connection to the internet with its own IP address, without a router), then you should use ufw to allow the OpenVPN port we have set up above (1194). Otherwise, we will set ufw to allow all traffic and configure the settings for routing.

If your Ubuntu server DOES NOT need ufw to protect it (i.e. it is behind a router or has a different firewall set up), you need to set the default input rule to allow all traffic to pass through ufw by default. To do so, we need to modify the configuration file.

  1. Open this file in nano:
    sudo nano /etc/default/ufw
  2. Scroll down to the section: 
    # Set the default input policy to ACCEPT, DROP, or REJECT. Please note that if
    # you change this you will most likely want to adjust your rules.
    DEFAULT_INPUT_POLICY="DROP"
  3. Since our server will not be using this firewall for protection, change this from "DROP" to "ACCEPT"
  4. Scroll down to the section: 
    # Set the default forward policy to ACCEPT, DROP or REJECT.  Please note that
    # if you change this you will most likely want to adjust your rules
    DEFAULT_FORWARD_POLICY="DROP"
  5. Change the forward policy from "DROP" to "ACCEPT"
  6. Press ctrl + x to exit nano. Save the changes when prompted.

If your Ubuntu server DOES need ufw to protect it, you need to tell it which ports to allow as it has the default input and forward policies of DROP. If you are running the OpenVPN server from some remote location, you will need to SSH into it to change any settings. As such, we need to tell the firewall to permit SSH traffic.

  1. Entering the following into the terminal:
    sudo ufw allow ssh
  2. The VPN traffic we will send to the OpenVPN server will be over UDP on port 1194, so enter into the terminal:
    sudo ufw allow 1194/udp

If you have other services running on your Ubuntu server, then you need to make sure that you allow their traffic through ufw as well. Make sure to add any allow rules for any other ports your Ubuntu server is listening on (such as a Plex media server or maybe your own email server).

Next, regardless of your network setup, you need to set up the routing rules for ufw.

  1. Open the ufw configuration file in nano:
    sudo nano /etc/ufw/before.rules
  2. Move the cursor below the section: 
    #
    # rules.before
    #
    # Rules that should be run before the ufw command line added rules. Custom
    # rules should be added to one of these chains:
    #   ufw-before-input
    #   ufw-before-output
    #   ufw-before-forward
  3. Paste in the following: 
    # START OPENVPN RULES
    # NAT table rules
    *nat
    :POSTROUTING ACCEPT [0:0]

    # Uncomment the next POSTROUTING line and replace ens224 with the name
    # of your Local Network Interface if you have a second network interface
    # for accessing machines on your local network
    # Allow OpenVPN client to communicate with local home network
    #-A POSTROUTING -s 10.8.0.0/24 -d 192.168.0.0/24 -o ens32 -j MASQUERADE

    # Allow traffic from OpenVPN client to your WAN and/or LAN via ens224
    -A POSTROUTING -s 10.8.0.0/24 -o ens224 -j MASQUERADE
    COMMIT
    # END OPENVPN RULES
    • Replace ens224 with the name of your Primary Network Interface if it is different (See Preparation section for more information)
  4. Move the cursor below the section: 
    # Don't delete these required lines, otherwise there will be errors
    *filter
    :ufw-before-input - [0:0]
    :ufw-before-output - [0:0]
    :ufw-before-forward - [0:0]
    :ufw-not-local - [0:0]
    # End required lines
  5. Paste in the following: 
    #Accept all traffic to and from VPN
    -A ufw-before-input -i tun+ -j ACCEPT
    -A ufw-before-output -i tun+ -j ACCEPT

    # Forward traffic to and from the VPN
    -A ufw-before-forward -s 10.8.0.0/24 -j ACCEPT
    -A ufw-before-forward -d 10.8.0.0/24 -j ACCEPT
  6. Press ctrl + x to exit nano. Save the changes when prompted.

Ufw is now ready to be activated.

  1. In the terminal, type:
    sudo ufw enable
  2. If you are SSH’d into this Ubuntu instance, it will display the prompt: 
    Command may disrupt existing ssh connections. Proceed with operation (y|n)?
    To which you should reply with y.

The following output will then be displayed (regardless of SSH or not) 

Firewall is active and enabled on system startup

Starting the OpenVPN Server

At this point the basics are complete. Your server configuration and files should be on your server, either generated on the server, or copied on from where you generated them.

First, create the OpenVPN server directory and copy the server configuration files to it using the commands below. Replace "/path/to/configs/server" with the correct path to where the files are on your server.

sudo mkdir -p /etc/openvpn/server
sudo cp /path/to/configs/server/* /etc/openvpn/server/

Now start your server, and enable it to start after a reboot as well.

The name after @ matches the server configuration filename without the .conf extension. As ovpngen creates server.conf by default, the service name is openvpn-server@server.

sudo systemctl enable openvpn-server@server
sudo systemctl start openvpn-server@server

To check the server status, enter:

sudo systemctl status openvpn-server@server

To which it should reply with:

Active: active (running)

If the server is not listed as active (running), you should see a log output displaying what has gone wrong. You can also view the OpenVPN server log by entering:

sudo journalctl -u openvpn-server@server -xe

Your OpenVPN server is now up and running and ready for you to connect to it.

Router Setup

If your Ubuntu server is directly accessible, then you can skip this section. There is no router to configure.

However if your Ubuntu server is behind a router (such as on your home WiFi), then you will need to configure your router to permit VPN traffic. Please see our Introduction to Running an OpenVPN Server Article for more information.

Optional: OpenVPN Data Channel Offload (DCO)

OpenVPN Data Channel Offload (DCO) can improve VPN performance by processing VPN data traffic in the Linux kernel instead of in the OpenVPN userspace process. It is of particular benefit to servers with multiple VPN clients, however even single-connection OpenVPN servers should see a noticeable performance improvement. This is optional, and the standard setup above will work without it.

DCO requires a compatible OpenVPN configuration. In particular, it requires a tun-style VPN, modern AEAD data ciphers, and no compression. If DCO is not available or the configuration is not compatible, OpenVPN should continue to run without DCO.

To check whether the DCO kernel module is available on your Ubuntu server, enter:

modinfo ovpn

If the command displays information about the module, load it with:

sudo modprobe ovpn

Then restart your OpenVPN server:

sudo systemctl restart openvpn-server@server

You can check the OpenVPN log to see whether DCO is being used:

sudo journalctl -u openvpn-server@server -b | grep -i dco

If you experience connection issues after enabling DCO, disable it by adding the following line to your server configuration:

disable-dco

Then restart OpenVPN again:

sudo systemctl restart openvpn-server@server

Setting Up Viscosity

The final step is to set up Viscosity. Thanks to ovpngen, this is as easy as importing and connecting.

Importing

Copy your *.visz file you created with ovpngen to your Mac or Windows machine with Viscosity installed and double click the file. You should see a prompt that the config was imported successfully.

Connecting and Using Your VPN Connection

You are now ready to connect. Click on the Viscosity icon in the macOS menu bar or Windows system tray to open the Viscosity Menu, select the connection you imported, and Viscosity will connect.

To check that the VPN is up and running, you can open the Details window from the Viscosity Menu. This will allow you to view connection details, traffic and the OpenVPN log.



 

That's it, you've set up your very own OpenVPN server. Congratulations, you are now free to enjoy the benefits of operating your own OpenVPN server!

Basic DNS Server

If you are electing to run your own DNS server for clients, the following is an example setup for dnsmasq.

You first need to disable systemd-resolved. This default service is restricted and won't allow us to listen for DNS requests over the VPN.

sudo systemctl disable systemd-resolved
sudo systemctl stop systemd-resolved
sudo unlink /etc/resolv.conf

Now create the resolv.conf file with the DNS server the Ubuntu server should use for lookups. Here we are using 8.8.8.8 (Google's Public DNS server), however you can replace that with a different address if desired.

echo "nameserver 8.8.8.8" | sudo tee /etc/resolv.conf

Now install dnsmasq with the following command:

sudo apt install -y dnsmasq

Next we need to modify some of the default configuration.

  1. Create a backup of the original dnsmasq configuration:
    sudo cp /etc/dnsmasq.conf /etc/dnsmasq.conf.bak
  2. Set the DNS server to listen for requests from the Ubuntu server (127.0.0.1) and from the VPN (10.8.0.1):
    printf "listen-address=127.0.0.1,10.8.0.1\nbind-interfaces\n" | sudo tee /etc/dnsmasq.conf
  3. Prevent our DNS requests from flooding the root DNS servers with bad requests:
    printf "domain-needed\nbogus-priv\n" | sudo tee -a /etc/dnsmasq.conf
  4. Use the Google DNS servers to resolve requests (you are free to use your DNS resolution service of choice):
    printf "server=8.8.8.8\nserver=8.8.4.4\n" | sudo tee -a /etc/dnsmasq.conf
  5. If you want to use friendly names for devices on your home/office network, add them to /etc/hosts. For example:
    echo "192.168.0.10 fileserver.home.arpa fileserver" | sudo tee -a /etc/hosts
  6. Restart the dnsmasq service to activate our changes:
    sudo systemctl restart dnsmasq

To check that the DNS server is listening on the addresses we requested, type:

sudo ss -ulpn | grep ':53'

You should see a list of addresses, including 127.0.0.1 and 10.8.0.1: 

State  Recv-Q Send-Q Local Address:Port  Peer Address:Port Process
...
UNCONN 0      0      127.0.0.1:53         0.0.0.0:*     users:(("dnsmasq",pid=54892,fd=6))
UNCONN 0      0      10.8.0.1:53          0.0.0.0:*     users:(("dnsmasq",pid=54892,fd=4))
...


Lastly, we need to ensure that dnsmasq is started after OpenVPN on system startup. By default, dnsmasq runs before OpenVPN, which prevents it from setting up the DNS server for the VPN as the VPN doesn't exist yet.

  1. Edit the OpenVPN server service:
    sudo systemctl edit openvpn-server@server
  2. Between the ### Anything between here and the comment below will become the new contents of the file and ### Lines below this comment will be discarded lines add the commands [Service] and ExecStartPost=/bin/systemctl restart dnsmasq so that it looks like:

    ### Anything between here and the comment below will become the new contents of the file

    [Service]
    ExecStartPost=/bin/systemctl restart dnsmasq

    ### Lines below this comment will be discarded
  3. Reload the service:
    sudo systemctl daemon-reload
    sudo systemctl restart openvpn-server@server

We are now done setting up the DNS server.