RICHARD BLUM has over 35 years of experience working as a system and network administrator. He teaches online courses in Linux and Web programming and is co-author with Christine Bresnahan of several Linux titles, including CompTIA Linux+ Study Guide, Linux Essentials, Mastering Linux System Administration, and the Linux Command Line and Shell Scripting Bible. CHRISTINE BRESNAHAN has over 35 years of experience working in the IT industry. She is an Adjunct Professor at Ivy Tech Community College where she teaches Linux certification and Python programming classes. She is co-author with Richard Blum of CompTIA Linux+ Study Guide, Linux Essentials, Mastering Linux System Administration, and the Linux Command Line and Shell Scripting Bible.