Certification is available for most areas of Linux but I think you're putting too much focus on it.
People predominately hire people who are competent at what they do, not the hoops they've jumped through to get there. A year of specific industry experience is worth a dozen vague certificates.
Even if you do want to continue down a road of certification-over-experience (which I can understand for somebody without much real-world experience), in order for the certificate to hold any value, it needs to be locked onto a real-world skill. Few companies will hire somebody solely on the basis that they have a "generic Linux certificate". If you want to be a DBA, get certified for MySQL or Oracle. If you want to be a network monkey, look through the various networking certification programmes available.
I'll add that the good certification programs are both quite hard and expensive (especially at the higher levels) and most of them rely on you having real-world experience for your reasoning.
And if you're applying for newly-grad/junior posts, people won't expect you to have put yourself through a certification programme anyway. They're looking to train up people.