DNS overview...

What is it?

The Domain Name System (DNS) translates Internet domain and host names to IP addresses. 

You can read the detail here

How does it work?

DNS Namespace (hierarchical structure):

DNS standard name resolution process:

Error 404

General: Differences between FTP and HTTP

Linux: creating a self-signed certificate...

A few simple commands to generate a self-signed certificate for your Linux server:

#mkdir -p /etc/ssl/private/

#openssl req -x509 -nodes -days 97300 -newkey rsa:2048 -keyout /etc/ssl/private/pure-ftpd.pem -out /etc/ssl/private/pure-ftpd.pem

#chmod 600 /etc/ssl/private/pure-ftpd.pem

General: Understanding load balancing...

Adding two new lines of Internet connections:

Then it will work this way by sharing equal loads between the three ISPs:

If one line cuts off, the remaining two lines will share equal loads again without causing problem. So, the Internet is still up and running.

This is why load balancing is cool. And it will work also with other thing like Apache web server as an example.

General: FTP server & Web server are working together...

General: Active and Passive FTP Transfer Modes

Linux: Free - How to use vim command - Cheat Sheet

Linux: Run Levels

Transport Layer 4: Port Numbers