Administration

Recently I was compiling a list of Linux commands that every sysadmin should know. One of the first commands that came to mind was nmap. nmap is a powerful network scanner used to identify systems and services. nmap was originally developed with network security in mind, it is a tool that was designed to find vulnerabilities within a network. nmap is more than just a simple port scanner though, you can use nmap to find specific versions of services, certain OS types, or even find that pesky printer someone put on your network without telling you....

In a world where the Anonymous group is petitioning the US Government to make DDoS attacks a legal means of protest; For internet facing systems the threat of Denial of Service attacks are very real. The cold harsh reality of DoS attacks are that there is no way to stop them. While there are services out there that are designed to take the brunt of the attack for you these costs a significant amount of money (update: CloudFlare seems pretty decent)....

For today's article I am going to explain how to create a basic firewall allow and deny filter list using the iptables package. We will be focused on creating a filtering rule-set for a basic everyday Linux web server running Web, FTP, SSH, MySQL, and DNS services. Before we begin lets get an understanding of iptables and firewall filtering in general. What is iptables? iptables is a package and kernel module for Linux that uses the netfilter hooks within the Linux kernel to provide filtering, network address translation, and packet mangling....

Zombies don't just appear in scary movies anymore, sometimes they also appear on your Linux systems; but don't fret they are mostly harmless. What is a Zombie Process? Before we get started I wanted to first cover what exactly a Zombie process is. Linux and Unix both have the ability for a process to create a sub process otherwise known as a “Child Process”. Once a process creates a new sub process the first process then becomes a “Parent Process” as it has spawned a child process during its execution....

Access Control Lists aka ACL's are one of those obscure Linux tools that isn't used every day; and if you find yourself using ACL's every day than you probably have a very complicated Linux environment. A few years ago I had an engineer tell me “Any thing you want to solve with ACL's can be solved with standard unix permissions” and while he may have just been justifying why he didn't know ACL's very well....