I would like to use
latexmk tools together with TeX Live 2012, but I could not find
latexmk. Is it extra tools, or did TeX Live stop supporting it?
In my case, I have OS Ubuntu 12.10.
There is a bit more detail in the docs for the script, but that should hopefully get you started.
Note that the 'recommended' way to have an up-to-date TeX system on Linux is to use the 'vanilla' TeX Live from TUG: How to install "vanilla" TeXLive on Debian or Ubuntu?.