Linux netinstall

Network bandwidth has grown so fast, do you still need DVD image to install your Linux? Over WAN, it looks a bit unsecure, but as long as you know where are you downloading the image, for Desktop users, it should be ok.

Net install(Netinstall) image

You can find netinstall image from the linux distribution website you like, burn it to CD/DVD, or to usb stick, there are many ways on web you can find.
Or use easier/general one, UNetbootin, it's GPL 2 free software, which allows you to create bootable Live USB drives for Ubuntu, Fedora, and other Linux distributions without burning a CD.  You can either let UNetbootin download one of the many distributions supported out-of-the-box for you, or supply your own Linux .iso file if you've already downloaded one or your preferred distribution isn't on the list.

Install

I tried two linux distributions, one is Fedora, the other is CentOS. Fedora is rather easy, you don't have to worry anything. For CentOS, you have to provide url where contains installation image. I don't want to go through it again for some people have don it already.
This one I found is quite good.

http://www.if-not-true-then-false.com/2011/centos-6-netinstall-network-installation/

The start page is different with UNetbotin screen, but it's not a big deal, For my self, I tried Fedora 19 and CentOS 6.5, both worked perfectly. For other linux distributions, if UNetbootin doesn't provides url, then find it by your self. I tried UNetbootin version 585.

Grub problem

This is the part CentOS should fix, via netinstall, for my case, bootloader wasn't correctly installed. By default, it points to /dev/sda1, but it was USB disk(case might be different in your case), but if I specify /dev/sdb1, which is the first hard driver partition, it won't work.
So, what I did was to just use USB disk as boot loader, of course to load installed CentOS(/dev/sda1), then did the following fix after boot.
USB disk became the last disk after boot, so what I did was to run

grub-install --boot-directory=/ --recheck /dev/sda

Then, made sure /boot/grub/grub.conf
splashimage=(hd0,0)/grub/splash.xpm.gz
...
    root (hd0,0)

Then, reboot without USB stick.