How to switch from SVR4/BSD internals to Linux internals?

Hello,

Long-time Unix hacker here - I've worked on four variants of the kernel prior to the introduction of Linux. In my spare time, I've written Linux (Ubuntu) device drivers, kernel modules, cross-compiled, and built the kernel.

I'd like to do Linux internals/device drivers as a day job, but every recruiter has said that unless I have "paid Linux experience" they won't submit my resume to their clientele - the ones with the jobs.

How did you make the jump to Linux at work? My employer has me maintaining a legacy OS and would prefer if I did NOT retrain. (I would have tried to jump ship long before now but had family commitments.)

Thank you!

Why is your employer not in favor of putting you on a relevant Linux course? Can you make the case to him/her that you would like to develop yourself into other areas, while still staying on for the legacy tasks, thereby making you more valuable for the firm?
Is there any point in asking to make a lateral move within the firm?
The other option I can think of is participating in an open source project with enough critical mass to also get noticed by future employers. It would also be a way to get in touch with like-minded developers who might give you advice on where else to look.