A Linux Grey Box QA Developer is a software quality assurance professional who works primarily with Linux systems. They are called 'grey box' testers because they have partial knowledge of the internal workings of the system. Their main role is to ensure the quality and efficiency of software by conducting rigorous testing. They design and execute grey box tests, which combine both black box (testing software without knowing its inner workings) and white box (testing with knowledge of the internal structure) techniques. They also debug issues, report defects, and work closely with development teams to ensure software reliability and performance.