Linux

"It's been my impression that the BSD communit{y,ies}, in general, understand Linux far better than the Linux communit{y,ies} understand BSD. I have a few theories on why that is, but that's not really relevant. I think a lot of Linux people get turned off BSD because they don't really understand how and why it's put together. Thus, this rant; as a BSD person, I want to try to explain how BSD works in a way that Linux people can absorb."

Chapter 1: Quick Introduction to Linux Chapter 2: Getting started with Shell Programming Chapter 3: Shells (bash) structured Language Constructs Chapter 4: Advanced Shell Scripting Commands Chapter 5: Essential Utilities for Power User

Overview of steps:

• Don’t panic. Keep your calm and develop a plan of actions
• Disconnect the system from the network
• Discover the method used to compromise the system
• Stop all the attacker scripts and remove his files
• Restore not affected services
• Fix the problem that caused the compromise
• Restore the affected services
• Monitor the system

Full article: How to restore a hacked Linux server

SS64.com is a useful site with:

• An A-Z Index of the Linux BASH command line.
• An A-Z Index of the Apple OS X command line.

"With proper use of groups, and a bit of scheduling, you don't need to hand out root [password]. In this article, we're going to implement group-based security for managing DNS files. The same techniques can be applied to almost any other section of the system." Full article: Using Groups to Eliminate Root