How to Install and Configure OpenVPN Server with Linux and Windows Clients in RHEL/CentOS 7

A Virtual Private Network is a technology solution used to provide privacy and security for inter-network connections. The most well-known case consists of people connecting to a remote server with traffic going through a public or insecure network (such as the Internet).

Picture the following scenarios:

OpenVPN Network Diagram

OpenVPN Network Diagram

In this article we will explain how to set up a VPN server in a RHEL/CentOS 7 box using OpenVPN, a robust and highly flexible tunneling application that uses the encryption, authentication, and certification features of the OpenSSL library. For simplicity we will only consider a case where the OpenVPN server acts as a secure Internet gateway for a client.

For this setup, we’ve used three machines, the first one act as a OpenVPN server and other two (Linux and Windows) act as a clients to connect to remote OpenVPN Server.

Note: The same instructions also works on RHEL/CentOS 6 and Fedora systems..

Installing OpenVPN Server

To install OpenVPN in a RHEL/CentOS 7 server, you will first have to enable the EPEL repository and then install the package, along with easy-rsa – a small RSA key management package used primarily for key management and also for building web certificates.

# yum update && yum install epel-release
# yum install openvpn easy-rsa

When the installation completes, head over to the sample configuration files directory:

# cd /usr/share/doc/openvpn-*/sample/sample-config-files/

and copy the server.conf file to /etc/openvpn:

# cp server.conf /etc/openvpn

Now we’re ready to start configuring the server.

Generate Keys and Certificates

The easy-rsa package provides several scripts as utilities, located inside /usr/share/easy-rsa/2.0 after installation, to generate keys and certificates. For our convenience, we are going to copy those files into /etc/openvpn/rsa (you need to create this directory first). Enter y if prompted to overwrite the existing files:

# mkdir /etc/openvpn/rsa
# cp –rf /usr/share/easy-rsa/2.0/* /etc/openvpn/rsa
Generate OpenVPN Keys and Certificates

Generate OpenVPN Keys and Certificates

Next, we will use the parameters in /etc/openvpn/rsa/vars to indicate the values for our keys and certificates. Change the values according to your needs (fields are self-explanatory):

export KEY_SIZE=2048
export CA_EXPIRE=365
export KEY_EXPIRE=365
export KEY_CITY="VillaMercedes"
export KEY_ORG=""
export KEY_EMAIL="[email protected]"
export KEY_NAME="GabrielCanepa"

And source the file to export the variables and their values to the current environment (you will need them in the next step). You will see a message informing you the purpose of the clean-all script (also present in the same directory):

# source ./vars
Export Keys and Certificates

Export Keys and Certificates

Now run the following scripts from the keys directory, in the specified order.

# ./clean-all

The build-ca script will create a Certificate Authority (certificate + key) in /etc/openvpn/rsa/keys. Press Enter to accept the default values:

OpenVPN Certificate Authority Key

OpenVPN Certificate Authority Key

Next, we will create the key and the certificate for the server itself. As before, accept the default values and then press y to confirm the signing of the certificate:

# ./build-key-server server
Create Keys and Certificates for Server

Create Keys and Certificates for Server

Next, generate the Diffie-Hellman file used for information exchange to complement RSA (this will take quite some time). This will create a file named dh2048.pem inside /etc/openvpn/rsa/keys:


Finally, create separate certificate files for each client that will use your VPN server (change client to a name of your choosing):

# ./build-key client

The above step will create a certificate and key for a client. Follow the same steps as before to complete the process. Later on this tutorial we will download these files to a client that will use them to connect to the VPN server.

Configuring the OpenVPN Server

Let’s now dive into /etc/openvpn/server.conf:

1. Specify the length of the Diffie-Hellman parameters. Don’t use a value below 2048 if you don’t want to expose yourself to security threats:

dh /etc/openvpn/rsa/keys/dh2048.pem

2. All IP traffic (such as web browsing and and DNS lookups) should go through the VPN. Make sure the following line is uncommented:

push "redirect-gateway def1 bypass-dhcp"

3. As a consequence of #2, you need to specify at least two DNS servers that will be used to resolve names. The default ones are provided by and you can either use them or Google’s ( and

push "dhcp-option DNS"
push "dhcp-option DNS"

4. Finally, as a security measure, we will ensure that openvpn runs with the least privilege by changing the user and the group to nobody:

user nobody
group nobody

We also need to allow vpn traffic through the firewalld and enable masquerading:

# firewall-cmd --permanent --add-service=openvpn
# firewall-cmd --add-service=openvpn
# firewall-cmd --permanent --add-masquerade
# firewall-cmd --add-masquerade

And copy the certificate and key files to /etc/openvpn (the following command assumes your current working directory is /etc/openvpn/rsa/keys):

# cp ca.crt server.crt server.key ../../

Then enable the service:

# systemctl -f enable [email protected]
# systemctl start [email protected]

At this point it’s a good idea to check the status of the service.

# systemctl -l status [email protected] 

If it failed to start,

# journalctl --xn

will provide necessary debug information to troubleshoot any issues.

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Gabriel Cánepa

Gabriel Cánepa is a GNU/Linux sysadmin and web developer from Villa Mercedes, San Luis, Argentina. He works for a worldwide leading consumer product company and takes great pleasure in using FOSS tools to increase productivity in all areas of his daily work.

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19 Responses

  1. Big Ian says:

    [[email protected] user]# yum install openvpn
    Loaded plugins: fastestmirror, langpacks
    Loading mirror speeds from cached hostfile
    * base:
    * extras:
    * updates:
    No package openvpn available.
    Error: Nothing to do

    • Ravi Saive says:

      @Big Ian,

      Have you installed epel-release package on the system? if not first install it as shown:

      # yum install epel-release

      Once epel installed, you can install openvpn.

      # yum install openvpn
  2. Patric S. says:

    I would use this Script from nyr. In my opinion is this the best alternative.


  3. Urs says:

    Small typo:
    cp ca.crt server.crt server.key /../.. (should be “../../”)

  4. dilan says:

    Please I am looking for how to install Open VPN Server on Linux, I want to run my computer..

  5. testsubject says:

    ca somethingelse.crt <—– shouldn't this be ca.crt?
    cert somethingelse.crt
    key somethingelse.key

  6. Ttlequals0 says:

    Here is an even quicker way of doing this that creates the Endpoint in any AWS region on demand.

  7. batisfera says:

    Obsolete already

  8. Nice article!
    Would love to see add user account, and point into different vlan

  9. pcasisten says:

    is there an error in that sentence?
    To set up a client (regardless of the distribution or operating system) you will need to copy the ca.crt, server.crt, and server.key files from /etc/openvpn/rsa/keys.

    wouldn’t be the client.crt and client.key files copied instead?

  10. cray says:

    journalctl –xn must be written with one dash, at least it is in Fedora. Double dash is not recognized

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