Unix-like operating systems have a primitive access control system. The root account can do anything. Other users are peasants with only minimal system access. Sudo lets you divide root’s monolithic power between the people who need it, with accountability and auditability.
While many people use sudo, most use only a small part of it’s features. Master sudo with Sudo Mastery.
DNS is one of the oldest protocols on the Internet, and was designed for a network without hostile users. Anyone who wants to break into a network starts by investigating the target's Domain Name Service. DNS Security Extensions, or DNSSEC, hardens DNS and brings it into the 21st century.
Secure Shell (SSH) lets systems administrators securely manage remote systems. But most people only use the bare minimum SSH offers. Used properly, SSH simplifies your job.
This book saves you from sifting a decade of obsolete online tutorials and quickly gets you running:SSH with the OpenSSH server and the PuTTY and OpenSSH clients.
Master SSH with SSH Mastery.