debian

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....

For todays article I wanted to put together a quick little cheat sheet for some GNU find command examples. Some of these commands will be basic some will be more advanced, but they all will be useful. As a caveat some commands don't work in all Unix environments and this is especially true with older releases. If you find yourself in one of those situations there is a way to make the find command work you will just need to use different methods like the -exec flag....

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....

I'm going to start this post by saying what I'm really thinking. 90% of the time if an application is running as the root user on a Unix/Linux machine; it is because the sysadmin who setup or designed the environment was being lazy. Now before getting offended, being a lazy sysadmin is a good thing. The fact is that most systems administrators are lazy in some way, and that is the reason why most systems administration tasks end up being scripted....

On System V based OS's the /etc/rc.local file is executed by the init process at the end of the systems boot process. The fact that the rc.local file is executed during the boot process makes it an easy target for misuse by lazy Sysadmins. Since I started my Unix experience on FreeBSD which relies primarily on the /etc/rc.* configuration files, I've seen and shamefully contributed to my fair share of misuse in the rc....