Linux Kernel Development, 2nd Edition
Embedded Linux kernel and driver development
Introduction to Linux
Bash Guide for Beginners
Advanced Bash-Scripting Guide
GNU/Linux Command-Line Tools Summary
Linux Filesystem Hierarchy
The Linux Kernel Module Programming Guide
The Linux System Administrator's Guide
Linux Network Administrators Guide
GNU/Linux advanced administration
Autobook: GNU Autoconf, Automake, and Libtool src
Understanding the Linux Virtual Memory Manager