How can I learn Hadoop big data online for free?

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I am beginner in Data Science and machine learning field. I am searching for the tutorials to learn:

How can I learn Hadoop big data online for free?

Try to provide me good examples or tutorials links so that I can learn the topic "How can I learn Hadoop big data online for free?". Also tell me which is the good training courses in Machine Learning, Artificial Intelligence and Data Science for beginners.

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