As someone who is moving into more of a devops role from a pure development role. Here is my learning list so far.

1. The TCP/IP Guide: A Comprehensive, Illustrated Internet Protocols Reference. http://www.amazon.com/The-TCP-Guide-Comprehensive-Illustrate...

2. Advanced Programming in the UNIX Environment http://www.amazon.com/Programming-Environment-Addison-Wesley...

3. A systems programming language- I choose golang.

4. GDB/makefiles

5. SSH, The Secure Shell: The Definitive Guide: The Definitive Guide http://www.amazon.com/SSH-Secure-Shell-Definitive-Guide-eboo...