[drablyechoes]

Topics to study should include: Unix IPC, signals and syscalls, filesystem and kernel implementation details, and network/socket programming.

Being able to read and write C programs goes a really long way.

Beej's guides are a good resource. I learned a lot from them.

Guide to network programming: https://beej.us/guide/bgnet/html/multi/index.html

Guide to Unix IPC: https://beej.us/guide/bgipc/

The Unix Programming Environment (Kernighan & Pike) is also very good.

http://files.catwell.info/misc/mirror/the-unix-programming-e...

A good exercise would be to write a simple IRC-like chat server and client in C.