Personally, what I would do is to "get a job ... any job ..." in a Linux-based shop. Then, once you're "in," be very attentive to everything that's going on around you, except that you purposely turn your head whenever a password of any sort is being entered. As people give you things to do – and they will be small things, at first – diligently do them. Ask questions freely: it's far better to ask, than to not-ask.
In this way, you begin to build up trust in the minds of the others. That's key.
Perhaps, later down the line, you'll be offered a chance to attend professional-training courses (which may or may not lead to "certifications"), at your employer's expense, and if that happens take advantage of it. But, don't look for "shortcuts," and don't try too hard to specialize.