For example if I have 4 computers and I want to install Linux to all these, what is the fastest way to install multiple computers at the same time and how ? For example our school has computer classes and if I need to try something which needs multiple computers how can I quickly set them up ? I was thinking that if I create a image first and then somehow install it via network boot ? Suggestions ? Using Xubuntu.
You can use Cobbler.
It has a nice web interface to manage your deployment image and you can create seed and kickstart file to automate install.
You can create system profiles by mac address to automatically choose the good kickstart file.
Likely the best way would be to use Ghost software to create an image of your setup and put it on a portable device of your choice to implement on a new system. Assuming you have one copy you can probably do four computers in under an hour. Clonezilla will do this for you just fine, or you can select whichever one you want.
Just bare in mind you will need to set your IP etc as you go along, since you don't want this mirrored.