How to make a mac os x iso file?

I have two laptops: a mac os x, and a windows/ubuntu. I want to have all three on one computer, but since the mac came without an install dvd, i need to make an iso of it to install it onto my other laptop. Any ideas on how to do that? Thanks in advance.
Update: the whole world already does have a free operating system: ubuntu. Its way better than windows, because it's a lot faster.
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