I haven't read it yet, but the linked report may have the answer:
The 2013 Linux Jobs Report, conducted by Dice, [...] includes insights into why employers are seeking Linux talent now and what the top incentives are for Linux pros, among other important findings. Download the complete report [1]today.
By looking at the infograph, it seems developers, syadmins, and devops are amongst these 'UNIX pros', so not really kernel hackers. I'd assume few companies are in need of 'kernel hacking skills'.
I think a lot of people assume Linux pro means kernel dev or someone who writes software for Linux but my take, here at least, is that Linux pro encompasses server admins and people familiar with Linux on a networking / infrastructure level.
I think the distinction he was trying to make is that UNIX skills are those that are transferable between UNIX modelled OS's e.g. shell programming, administration, application development. Whereas a Linux pro would be someone whose skills are specifically on that platform. The most obvious reason being kernel programming expertise which is almost the epitome/definition of Linux.
Could also be someone from a Unix background that also knows specifics of how to optimally manage typical Linux business deployments (usually RHEL, SLES, etc). I can't tell you how many long-time Unix admins I've worked with that didn't know anything about how to create a start/stop init script that was chkconfig compliant (chkconfig originated from Irix I belive), and end up making symlinks in /etc/rcX.d manually. Or be able to debug boot problems (requires knowledge of at least some kernel boot parameters, the initrd, order of the various startup scripts, etc).
A short list:
- Systems monitoring and being able to recognize and resolve performance problems
- Being able to fix/compile/modify/package software
- Being somewhat of a polyglot. Knowing shell, a few scripting languages, config languages, regular expressions, etc.
- Being able to identify and fix hardware related issues