My Cloud is in my Pocket

I don´t know if many people do this. But personally I can´t live without my “cloud” in my pocket. I have different Macs. At home I have a big iMac. At work I have another one. I also have a MacBookPro that I carry around sometimes but I find it very heavy and with a horrible tendency to overheat. But even though I use 3 different Macs I have a system by which they are constantly cloned. Whenever I use a Mac I use an external bootable 500GB HP hardrive. I use the same HD whatever Mac I use. Whenever I start with a new Mac I boot off my HD by pressing Power and ALT at the same time. So in the end I always have the same info whatever Mac I use. So what I take around is a HD in my pocket, not a laptop, my pocket cloud. I have not found a way to do this with Linux, nor with Windows.