Make a strong portfolio by adding your work in GitHub and writing blogs explaining your projects. Find some good online courses on Hadoop that provides certification also. Add those certifications in your Linkedin profile. Research on the internet for most frequently asked questions in Hadoop developer Interviews.
I recommend this course for Hadoop Certification by Intellipaat. You can go through this blog on most frequently asked Hadoop Interview Questions to crack a Hadoop developer interview.
You can watch this video on how to become a Hadoop developer to know more about this Hadoop certification: