I'd argue every programmer. It's such a fundamental part of computers & operating systems that key concepts will come up again and again. Just the other day I wanted to learn about Docker/CoreOS/etcd only to realize that I have an embarrassingly lacking understanding of how UNIX works. I immediately went to the library to pick up this book and begin fixing a flaw of mine (even as a web developer).
Meh. Not all programmers are on a UNIX system. Not all programmers are even on UNIX || Window.XX.
But even if there was only UNIX... the entire point of a well designed system is to allow users of the system to reason about it on a high level, not a domain-expert level or even domain-intermediate level. As programmers we reason about code without worrying too much about gate layout on silicon. As non-system programmers we should likewise not need to worry about shoddy OS design.
I'd argue every programmer. It's such a fundamental part of computers & operating systems that key concepts will come up again and again. Just the other day I wanted to learn about Docker/CoreOS/etcd only to realize that I have an embarrassingly lacking understanding of how UNIX works. I immediately went to the library to pick up this book and begin fixing a flaw of mine (even as a web developer).