(Last Updated On: May 21, 2019)

This guide will explain how to install and configure OpenVPN Server on RHEL / CentOS 8. A Virtual Private Network (VPN) allows you to traverse untrusted networks securely as if you were within a secure LAN network. OpenVPN is a full-featured, open-source Secure Socket Layer (SSL) VPN solution that supports a wide range of configurations.

With OpenVPN, you can easily set a secure tunnel that extends private network across a public network. All traffic being sent is encrypted and you can trust the information received on the other end. In this blog post, we will explore an easy way of installing and configuring OpenVPN server on RHEL / CentOS 8 server.

Install OpenVPN Server on RHEL / CentOS 8

There are two options of setting up OpenVPN server on RHEL / CentOS 8.

  1. Installing OpenVPN server manually – Time consuming
  2. Install OpenVPN server using automated scripts – Easy and quick

This guide will focus on using a trusted script to install and configure OpenVPN server. We will use openvpn-install script which let you set up your own VPN server in no more than a minute, even if you haven’t used OpenVPN before. It has been designed to be as unobtrusive and universal as possible.

Step 1: Add EPEL and Install git

Add EPEL repository to your RHEL / CentOS 8 system. It has openvpn package and dependencies required.

How to Install EPEL Repository on RHEL / CentOS 8

We also need git to pull the code from Github. Ensure it is installed.

sudo dnf -y install git

Step 2: Clone openvpn-install repository

Now clone the openvpn-install repository using git tool installed in Step one:

$ cd ~
$ git clone https://github.com/Nyr/openvpn-install.git
Cloning into 'openvpn-install'…
remote: Enumerating objects: 360, done.
remote: Total 360 (delta 0), reused 0 (delta 0), pack-reused 360
Receiving objects: 100% (360/360), 104.04 KiB | 263.00 KiB/s, done.
Resolving deltas: 100% (180/180), done.

Step 3: Run OpenVPN installer

Switch to the openvpn-install directory and run the installer script.

$ chmod +x openvpn-install.sh
$ sudo ./openvpn-install.sh

You will get a couple of prompts to change or confirm default settings for the installation.

Welcome to this OpenVPN "road warrior" installer!
I need to ask you a few questions before starting the setup.
You can leave the default options and just press enter if you are ok with them.
First, provide the IPv4 address of the network interface you want OpenVPN
listening to.
IP address: 192.168.122.198
This server is behind NAT. What is the public IPv4 address or hostname?
Public IP address / hostname: vpn.example.com
Which protocol do you want for OpenVPN connections?
1) UDP (recommended)
2) TCP
Protocol [1-2]: 1
What port do you want OpenVPN listening to?
Port: 1194
Which DNS do you want to use with the VPN?
1) Current system resolvers
2) 1.1.1.1
3) Google
4) OpenDNS
5) Verisign
DNS [1-5]: 1
Finally, tell me your name for the client certificate.
Please, use one word only, no special characters.
Client name: computingforgeeks
Okay, that was all I needed. We are ready to set up your OpenVPN server now.
Press any key to continue…
Updating Subscription Management repositories.
Updating Subscription Management repositories.
Extra Packages for Enterprise Linux 7 - x86_64 189 kB/s | 16 MB 01:24
Last metadata expiration check: 0:00:54 ago on Wed 20 Mar 2019 07:23:31 PM EAT.
Package epel-release-7-11.noarch is already installed.
Dependencies resolved.
Nothing to do.
Complete!
Updating Subscription Management repositories.
Updating Subscription Management repositories.
Waiting for process with pid 1906 to finish.
Package iptables-1.8.0-11.el8.x86_64 is already installed.
Package openssl-1:1.1.1-6.el8.x86_64 is already installed.
Package ca-certificates-2018.2.24-6.el8.noarch is already installed.
Dependencies resolved.
Package Arch Version Repository Size
Installing:
openvpn x86_64 2.4.7-1.el7 epel 522 k
Installing dependencies:
pkcs11-helper x86_64 1.11-3.el7 epel 56 k
libnsl x86_64 2.28-18.el8 rhel-8-for-x86_64-baseos-beta-rpms 84 k
compat-openssl10 x86_64 1:1.0.2o-3.el8 rhel-8-for-x86_64-baseos-beta-rpms 1.1 M
Transaction Summary
Install 4 Packages
Total download size: 1.8 M
Installed size: 4.6 M
Downloading Packages:
(1/4): pkcs11-helper-1.11-3.el7.x86_64.rpm 34 kB/s | 56 kB 00:01
(2/4): openvpn-2.4.7-1.el7.x86_64.rpm 191 kB/s | 522 kB 00:02
(3/4): libnsl-2.28-18.el8.x86_64.rpm 26 kB/s | 84 kB 00:03
(4/4): compat-openssl10-1.0.2o-3.el8.x86_64.rpm
.......................

You need to set:

  • Server’s IP address to be used by VPN
  • The hostname of Server if inside NAT
  • OpenVPN protocol to be used – TCP or UDP
  • OpenVPN port
  • DNS Nameserver to be used with VPN
  • Name of first client profile to create

If the installation was successful, you should receive message similar to one below.

..............
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
commonName :ASN.1 12:'computingforgeeks'
Certificate is to be certified until Mar 17 16:24:47 2029 GMT (3650 days)
Write out database with 1 new entries
Data Base Updated
Using SSL: openssl OpenSSL 1.1.1 FIPS 11 Sep 2018
Using configuration from /etc/openvpn/easy-rsa/pki/safessl-easyrsa.cnf
Can't load /etc/openvpn/easy-rsa/pki/.rnd into RNG
140135296710464:error:2406F079:random number generator:RAND_load_file:Cannot open file:crypto/rand/randfile.c:90:Filename=/etc/openvpn/easy-rsa/pki/.rnd
An updated CRL has been created.
CRL file: /etc/openvpn/easy-rsa/pki/crl.pem
788
success
success
success
success
success
success
612
Created symlink /etc/systemd/system/multi-user.target.wants/[email protected] → /usr/lib/systemd/system/[email protected]
Finished!
Your client configuration is available at: /root/computingforgeeks.ovpn
If you want to add more clients, you simply need to run this script again!

The main OpenVPN server configuration file is,/etc/openvpn/server.conf you are free to tune it to your liking.

$ cat  /etc/openvpn/server.conf 
port 1194
proto udp
dev tun
sndbuf 0
rcvbuf 0
ca ca.crt
cert server.crt
key server.key
dh dh.pem
auth SHA512
tls-auth ta.key 0
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS 192.168.122.1"
keepalive 10 120
cipher AES-256-CBC
user nobody
group nobody
persist-key
persist-tun
status openvpn-status.log
verb 3
crl-verify crl.pem

A  tun0 virtual interface will be created during the setup process. This is used by OpenVPN clients subnet.

$ ip addr | grep tun0
3: tun0: mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 100
inet 10.8.0.1/24 brd 10.8.0.255 scope global tun0

The default subnet for this interface is.10.8.0.0/24.OpenVPN server will be assigned 10.8.0.1 IP address:

Step 3: Generate OpenVPN user profile (.ovpn file)

After completing step 1 through 3, your VPN Server is ready for use. We need to generate VPN Profiles to be used by the users. The same script we used for the installation will be used for this. It manages the creation and revocation of user profiles.

Run script and select 1 to add new user.

$ sudo ./openvpn-install.sh

Looks like OpenVPN is already installed.
What do you want to do?
1) Add a new user
2) Revoke an existing user
3) Remove OpenVPN
4) Exit
Select an option [1-4]: 1
Tell me a name for the client certificate.
Please, use one word only, no special characters.
Client name: user1
Using SSL: openssl OpenSSL 1.1.1 FIPS 11 Sep 2018
Can't load /etc/openvpn/easy-rsa/pki/.rnd into RNG
139966006863680:error:2406F079:random number generator:RAND_load_file:Cannot open file:crypto/rand/randfile.c:90:Filename=/etc/openvpn/easy-rsa/pki/.rnd
Generating a RSA private key
……………………………………………………………………..+++++
……………………………………….+++++
writing new private key to '/etc/openvpn/easy-rsa/pki/private/user1.key.SeCj8ncgaH'
Using configuration from /etc/openvpn/easy-rsa/pki/safessl-easyrsa.cnf
Can't load /etc/openvpn/easy-rsa/pki/.rnd into RNG
139828629223232:error:2406F079:random number generator:RAND_load_file:Cannot open file:crypto/rand/randfile.c:90:Filename=/etc/openvpn/easy-rsa/pki/.rnd
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
commonName :ASN.1 12:'user1'
Certificate is to be certified until Mar 17 16:48:32 2029 GMT (3650 days)
Write out database with 1 new entries
Data Base Updated
Client user1 added, configuration is available at: /root/user1.ovpn

The .ovpn OpenVPN profile file is placed inside /root folder.

$ sudo ls /root/ | grep ovpn
computingforgeeks.ovpn
user1.ovpn

Revoking OpenVPN user profile

To revoke a user profile, run the script and select 2.

$ sudo ./openvpn-install.sh
Looks like OpenVPN is already installed.
What do you want to do?
1) Add a new user
2) Revoke an existing user
3) Remove OpenVPN
4) Exit
Select an option [1-4]: 2
Select the existing client certificate you want to revoke:
1) computingforgeeks
2) user1
Select one client [1-2]: 2
Do you really want to revoke access for client user1? [y/N]: y
Using configuration from /etc/openvpn/easy-rsa/pki/safessl-easyrsa.cnf
Can't load /etc/openvpn/easy-rsa/pki/.rnd into RNG
140410149218112:error:2406F079:random number generator:RAND_load_file:Cannot open file:crypto/rand/randfile.c:90:Filename=/etc/openvpn/easy-rsa/pki/.rnd
Revoking Certificate FAC5CC0C127D1242CC55BD31B7FB27D3.
Data Base Updated
Using SSL: openssl OpenSSL 1.1.1 FIPS 11 Sep 2018
Using configuration from /etc/openvpn/easy-rsa/pki/safessl-easyrsa.cnf
Can't load /etc/openvpn/easy-rsa/pki/.rnd into RNG
139874879330112:error:2406F079:random number generator:RAND_load_file:Cannot open file:crypto/rand/randfile.c:90:Filename=/etc/openvpn/easy-rsa/pki/.rnd
An updated CRL has been created.
CRL file: /etc/openvpn/easy-rsa/pki/crl.pem
Certificate for client user1 revoked!

Uninstalling OpenVPN server on RHEL / CentOS 8

If you no longer need OpenVPN server, uninstallation can be done using the same installer script.

$ sudo ./openvpn-install.sh
Looks like OpenVPN is already installed.
What do you want to do?
1) Add a new user
2) Revoke an existing user
3) Remove OpenVPN
4) Exit
Select an option [1-4]: 3
Do you really want to remove OpenVPN? [y/N]: y
788
success
success
success
success
success
success
Updating Subscription Management repositories.
Updating Subscription Management repositories.
Dependencies resolved.
....
Complete!
OpenVPN removed!

Step 4: Connect to OpenVPN Server from the client

You can use the VPN client of your choice to configure OpenVPN client on your operating system. For those who want to use Official OpenVPN client, go to the downloads page and get the latest release then install it.

Once Installed, on Windows, navigate to the directory with the ovpn profile, right click on the file name and select “Start OpenVPN on this config file

For Linux users, you can use NetworkManager and openvpn plugin to connect to OpenVPN server. Check my previous guide for how to: How to use nmcli to connect to OpenVPN Server on Linux.

Conclusion

You have successfully installed the OpenVPN server on RHEL/CentOS 8. The computers at each end of the VPN tunnel will encrypt the data entering the tunnel and is decrypted at the other end. Check OpenVPN documentation for more configuration options.

You can check other VPN related articles available in our blog.

Algo VPN – Setup a personal IPSEC VPN in the Cloud

How to Setup IPSec VPN server with L2TP and Cisco IPsec on Linux

How to use nmcli to connect to OpenVPN Server on Linux

How to connect to VPN Server with OpenConnect SSL VPN Client on Linux

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