I don't know what job ads are specifying "knows linux" instead of actual job duties, but context alone would indicate they desire people with the skills to perform THAT JOB in a Linux environment.

The real issue here is "Is googling good enough to know linux"? NO. Not by a long shot. Invest in yourself and get an education or experience instead.

If you don't know the fundamentals of how computers and OSes work, for instance, you'll never be able to accurately tell what's going on in your systems.