HOW TO INSTALL OPENVPN on CENTOS

hope this will be useful 
==================== 
1. enter to your server via putty
2. have to login with root access
---
ensure TUN TAP is activated
enter this command :
cat /dev/net/tun
the answer must be : file descriptor in bad state 
---------------------------------
3. and then entering this command :
CENTOS 5 32bit

wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm

CENTOS 5 64bit

wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.x86_64.rpm

CENTOS 6 32 bit

wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.i686.rpm

CENTOS 6 64bit

wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm

ALL CENTOS 5 

rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt

rpm -K rpmforge-release-0.5.2-2.el5.rf.*.rpm

rpm -i rpmforge-release-0.5.2-2.el5.rf.*.rpm

ALL CENTOS 6 

rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt (abaikan jika gagal)

rpm -K rpmforge-release-0.5.3-1.el6.rf.*.rpm

rpm -i rpmforge-release-0.5.3-1.el6.rf.*.rpm

yum install openvpn -y

cp -r /usr/share/doc/openvpn-2.2.2/easy-rsa/ /etc/openvpn/

PLEASE NOTICE CENTOS 6
Need little change
yum -y install nano
nano /etc/openvpn/easy-rsa/2.0/vars

you have to edit this line : 

export KEY_CONFIG=`$EASY_RSA/whichopensslcnf $EASY_RSA`

to  :

export KEY_CONFIG=/etc/openvpn/easy-rsa/2.0/openssl-1.0.0.cnf

and then SAVE (Ctrl+x) (Y) (ENTER)

cd /etc/openvpn/easy-rsa/2.0/

chmod +x *

source ./vars

./vars

./clean-all

./build-ca

press enter in all choice EXCEPT COMMON NAME (fill it as your desire)
then :

./build-key-server server

watch this step carefully 
when notification showed up (twice) choose Y (y)
----------------------------------------

./build-dh

wait til the process is done
if so, enter this command :

cp -r /etc/openvpn/easy-rsa/2.0/keys/ /etc/openvpn/keys/

cp /etc/openvpn/keys/ca.crt /etc/openvpn/ 

cd /etc/openvpn/

making Response to TUN driver

cat > server.conf <<END

dev tun*

END 

Making Server Configuration :

cat > groundworld.conf <<END

port 443
proto tcp
dev tun
ca /etc/openvpn/keys/ca.crt
cert /etc/openvpn/keys/server.crt
key /etc/openvpn/keys/server.key
dh /etc/openvpn/keys/dh1024.pem
plugin /usr/share/openvpn/plugin/lib/openvpn-auth-pam.so /etc/pam.d/login
client-cert-not-required
username-as-common-name
server 10.9.8.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "redirect-gateway def1"
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"
keepalive 5 30
comp-lzo
persist-key
persist-tun
status server-tcp.log
verb 3
END

 Forwarding Port

echo 1 > /proc/sys/net/ipv4/ip_forward

Iptables Route rules

iptables -t nat -A POSTROUTING -s 10.9.8.0/24 -o venet0 -j SNAT --to xxx.xxx.xxx.xxx

xxx.xxx.xxx.xxx above have to be changed with your VPS IP ADDRESS
 Run VPN on your server: 

service openvpn start