Yearly Archives: 2016

Setting up ReactJS Development environment with Babel and WebPack

This quick guide is to help you setup ReactJS Development environment with Babel and WebPack. The post is mostly copied from Source: I post it here for later personal reference. Let’s start from scratch Create a new folder ‘react-hello-world’ and initialize it with npm. [bash]mkdir react-hello-world cd react-hello-world npm init[/bash] […]

Running Selenium with FireFox browser in CentOS

Quick note here the necessary steps to install and run Selenium with FireFox browser in CentOS. We will need to setup XWindows for Headless Selenium with FireFox webdriver. First, install Xvfb: [bash]yum -y install firefox Xvfb libXfont Xorg[/bash] Then, install X-desktop: [bash]yum -y groupinstall "X Window System" "Desktop" "Fonts" "General Purpose […]

OpenVPN installation quick tutorial

Just a quick introduction for OpenVPN installation since there is a good work from that helps install in 1-click. I just add some extra notes when installing as well as connecting for future references. First, run the one-step installation command: [bash]wget -O && bash[/bash] When installing, just remember to […]

Install OpenVPN server CentOS 7

Today I will brief necessary steps for installing OpenVPN server CentOS 7. This will include custom server name and also rules for csf firewall which is widely used. The OpenVPN server name in this tutorial will be myvpnserver, associated domain will be, and server IP address is XXX.YYY.ZZZ.UUU . We […]

Migrate Gitlab to new server

When migrating gitlab to a new server, you might face much problems of in-compatible versions, different OS (so different latest gitlab version), etc. The best way is to upgrade the old server to the same latest gitlab version, then backup gitlab, and then transfer the backup to the new server, […]

Real IP from Amazon Load Balancers

If you are running an EC2 instance behind an Amazon Elastic Load Balancer (ELB), you’ll find that the visitors’ IPs are hided behind the load balancer, so your application cannot get the clients’ real IPs. In fact, visitors’ original IPs are passed via a X-Forwarded-For information in the header (, […]