Note: “i686” is a 32-bit system while “x86_64” is a 64-bit one (that is why you got “cannot execute binary file: Exec format error”).
You need a “x86_64” system if you want to use the “binary distribution” provided by the ROOT team (you do not need to rebuild ROOT, unless you need some features which are missing in this particular “binary distribution”, but can be “switched on” when you build your own ROOT version).
If you want ROOT on your “i686” system, you will need to compile it yourself using the “source code”.
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