2.1 Austerity, the study of sacred texts, and the dedication of action to God constitute the discipline of Mystic Union.
Time to move on to Book 2 of the Yoga Sutras. Book One focuses more on the philosophical side of Yoga, while Book Two focuses more on spiritual practices and disciplines. Just like in Book One, there are not any specific breathing, poses, or meditation techniques given. It's just another basic guideline for practice.
Sutra 2.1 opens the book with a broad brush stroke, giving us the basic types of discipline one can use to reach enlightenment. Some schools preach using one, parts of others or all of them. I think any practitioner should use the vast array of techniques and methods to see which ones works best. When you find one that does the trick, pound on it like a jackhammer. The tricky thing about Yoga is that it's not a linear path. Many times it will seem like you have taken two steps forward, only to realize that you lost what you had. Sometimes things will happen out of nowhere and you can spend years trying to get the same experience only to find it was not as great as the first time.
Austerity, in Yoga has different levels. Mental austerity is the process of changing unneeded though patterns. Physical austerity is trying to get the most out of using the least. I have yet to see a Yogi on Hoarders. Verbal austerity means being conscious of our words and the impact they have on the world around us. So we learn to do more with less.
Study of sacred text does not limit itself to the Vedas. I think of it as indulging yourself in anything that expands your self awareness. If you are an engineer, have you bothered to read the Twilight series? We love to mock it, but it is still something you have yet to experience for yourself. It's the sacred text of sparkly vampires.
Dedication of actions to God is another meaning of detachment. Working in the world in the light of truth without regard to outcome and selfless action are examples, if not the same thing.