You dont have to have a Linux certification to get a job working with Linux, but it cant hurt.
Simply working on Linux is easy. Join a Linux community like The Debian Project, Red Hats Fedora, Novells OpenSUSE, or half-a-hundred projects and go for it.
Of course, you wont get paid, and 95 percent of the work on Linux projects is programming. So, if you want a salary, and your skills lie in system administration or network management, it behooves you to look into Linux certifications.
Of course, a Linux certification doesnt mean a darn thing in and of itself. I havent met a standardized test yet that I couldnt beat. It doesnt mean I know anything. Im just one of those people who test well.
What really counts is the ability to take Linux and make it jump up and down and do the work that todays companies need done. The only way to really show that you have those skills is by doing the work.
That said, as Linux increasingly is entering businesses front doors rather than as a skunk-works project in the back-room, the people hiring Linux-workers are more likely to be in human resources than in IT.
That, in turn, means youre more likely to be judged by your degrees and certifications than by your experience and skills.
But, which certification? Aye, theres the rub.