In this guide, we’ll show you how to set up and install an OpenVPN on CentOS 5 and CentOS 6 server – At the end of this guide, you’ll have successfully installed OpenVPN on your server. A VPN stands for Virtual Private Network. It creates a secure connection between 2 or more than two devices. VPN is a connection used to add privacy to public and private networks. VPN is used by the individuals and companies to protect their sensitive data and information.
When combined with HTTPS connections, this setup permits you to secure your wireless logins and transactions. OpenVPN is a full-featured, ASCII document Secure Socket Layer (SSL) VPN resolution that accommodates an oversized vary of configurations.
- OpenVZ based server (Recommended). Other types of servers such as Xen/KVM should work fine too, but you might encounter some additional problems during the installation process.
- Your server’s operating system should be CentOS 5 or CentOS 6 (This guide will not work for any other Linux distributions).
- TUN/TAP enabled on the server; You can use below command to check.
The first step is to examine if TUN/TAP is enabled on your server or not by typing this command in your SSH:
If TUN/TAP is enabled then you should see this:
cat: /dev/net/tun: File descriptor in bad state
If it’s not turned on, then you must search for TUN/TAP in your server control panel and allow it or contact your hosting.
Installing some required packages
Let’s first check for server updates:
yum update -y
Install the required package for OpenVPN:
yum install gcc make rpm-build autoconf.noarch zlib-devel pam-devel openssl-devel nano -y
Download LZO RPM and Configure RPMForge Repo:
RPMForge 32-bit Package:
RPMForge 64-bit Package:
Build the rpm packages:
rpmbuild --rebuild lzo-1.08-4.rf.src.rpm rpm -Uvh lzo-*.rpm rpm -Uvh rpmforge-release*
Set Up and Installing OpenVPN on CentOS (5 and 6)
yum install openvpn -y
Copy the easy-rsa folder to /etc/openvpn/:
cp -R /usr/share/doc/openvpn-2.2.2/easy-rsa/ /etc/openvpn/
Note: If you are using the above commands and if it brings an error like below then you shouldn’t worry about it, follow the below steps to transfer and copy easy-rsa as it’s not included with the new build OpenVPN 2.3.1:
cannot stat `/usr/share/doc/openvpn-2.2.2/easy-rsa/’: No such file or directory
Download easy-rsa from below:
Extract the package:
tar -zxvf easy-rsa-2.2.0_master.tar.gz
Copy to OpenVPN directory:
cp -R easy-rsa-2.2.0_master/easy-rsa/ /etc/openvpn/
Please note on CentOS 6 we need to make a small change before you run the commands below, open up /etc/openvpn/easy-rsa/2.0/vars and edit the below line:
export KEY_CONFIG=`$EASY_RSA/whichopensslcnf $EASY_RSA`
Now let’s create the certificate:
cd /etc/openvpn/easy-rsa/2.0 chmod 755 * source ./vars ./vars ./clean-all
Country Name: may be filled or press enter State or Province Name: may be filled or press enter City: may be filled or press enter Org Name: may be filled or press enter Org Unit Name: may be filled or press enter Common Name: your server hostname Email Address: may be filled or press enter
Build key server:
Almost the same with ./build.ca but check the changes and additional Common Name: server A challenge password: leave Optional company name: fill or enter sign the certificate: y 1 out of 1 certificate requests: y
Wait a moment until the process finish:
Now create your config file:
touch /etc/openvpn/server.conf vi /etc/openvpn/server.conf
And enter the following:
port 1194 #- port proto udp #- protocol dev tun tun-mtu 1500 tun-mtu-extra 32 mssfix 1450 reneg-sec 0 ca /etc/openvpn/easy-rsa/2.0/keys/ca.crt cert /etc/openvpn/easy-rsa/2.0/keys/server.crt key /etc/openvpn/easy-rsa/2.0/keys/server.key dh /etc/openvpn/easy-rsa/2.0/keys/dh1024.pem plugin /usr/share/openvpn/plugin/lib/openvpn-auth-pam.so /etc/pam.d/login #- Comment this line if you are using FreeRADIUS #plugin /etc/openvpn/radiusplugin.so /etc/openvpn/radiusplugin.cnf #- Uncomment this line if you are using FreeRADIUS client-cert-not-required username-as-common-name server 10.8.0.0 255.255.255.0 push "redirect-gateway def1" push "dhcp-option DNS 220.127.116.11" push "dhcp-option DNS 18.104.22.168" push "block-outside-dns" keepalive 5 30 comp-lzo persist-key persist-tun status 1194.log verb 3
Now before we start OpenVPN, Let’s first disable the SELinux. If it is left enabled then it can cause some issues with OpenVPN:
echo 0 > /selinux/enforce
This solution is a temporary and will be re-enabled once you boot your system, to disable it permanently you need to edit the following /etc/SELinux/config and change:
When your system next reboots it will still be disabled.
Now, let’s start OpenVPN:
service openvpn restart
Now we need to enable IP forwarding. So open the file /etc/sysctl.conf and set ‘net.ipv4.ip_forward’ to 1:
net.ipv4.ip_forward = 1
To make the changes to sysctl.conf take effect, use the following command.
The rule below will work fine on Xen and KVM based VPS’s but for OpenVZ use the OpenVZ iptable rule instead:
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
OpenVZ iptable rules:
iptables -t nat -A POSTROUTING -o venet0 -j SNAT --to-source 22.214.171.124
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -j SNAT --to-source 126.96.36.199
Make sure you change 188.8.131.52 to your server IP.
IF you have CSF on the same server you need to open your OpenVPN port (Usually 1194) through the firewall and run the below commands for CSF, also it’s a good idea to add them to /etc/csf/csfpre.sh.
iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT iptables -A FORWARD -j REJECT iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE iptables -t nat -A POSTROUTING -j SNAT --to-source 184.108.40.206
If the above rules cause you any problems or don’t seem to work (Especially on cPanel servers) then remove the rules above and use below:
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE iptables -A FORWARD -i tun0 -o eth0 -j ACCEPT iptables -A FORWARD -i eth0 -o tun0 -j ACCEPT
Please make sure 220.127.116.11 is your primary server IP.
service iptables save
Now create a server.ovpn config file and enter the following:
client dev tun proto udp remote 18.104.22.168 1194 # - Your server IP and OpenVPN Port resolv-retry infinite nobind tun-mtu 1500 tun-mtu-extra 32 mssfix 1450 persist-key persist-tun ca ca.crt auth-user-pass comp-lzo reneg-sec 0 verb 3
Make sure you change 22.214.171.124 to your server IP.
And make sure that OpenVPN starts at boot:
chkconfig openvpn on
Download ca.crt file in /etc/openvpn/easy-rsa/2.0/keys/ directory and place it in the same directory as your server.ovpn.
Congratulations! You have successfully installed an OpenVPN on CentOS 5 and CentOS 6 following this guide. As you know, VPN service is essential for businesses and individuals to protect their valuable data and information (for instance, secretive files, credit card details, passwords, and other credentials). We have designed an OpenVPN based management system that will enable you to run your VPN service in a few steps. It automizes everything for you; from sign up to termination. Take a look at our Homepage to learn more about us.