Unix/Linux Filesystem Permissions 101

Background Standard Unix filesystem permissions are less complex than Windows file system permissions and Linux ACLs. Though, this lacks flexibility which is sometimes needed, In many cases it can be leveraged as an advantage. Often the complexity of ACLs can allow administrators to create file system permissions which are cumbersome to audit and document. The

KVM Cluster with DRBD/GFS

Background Recently, I started a project at (www.eyemg.com) to migrate from VMWare to KVM. Our standard server deployment is based on RHEL5 running on HP DL380 hardware. Given our hardware/software deployment, it made sense to align ourselves with Red Hat’s offering of KVM. We are able to achieve feature parity with VMware server while adding

Snort Alert Log: Simple Analysis and Daily Reporting with Arnold and Petit

Background This script was developed last year to give a quick and dirty analysis of the Snort alert log. In typical fashion, it’s is far from perfect, but approximately right is better than absolutely wrong. Obviously, the intersects could be combined in new and creative ways, this is just one that works for us. Also,

Centralized Logging System, Analysis, and Troubleshooting

Background Building a feature complete centralized logging system that provided the ability to trouble shoot problems and pro-actively find new issues before they became service outages was a top priority when I first started at (www.eyemg.com). I call it feature complete because it has successfully done both for us without spending too much time of

DevOps Toolchain: Problems with Automated Deployment, Data & Workflow

Background Automated deployment is obviously not new, but until this point, there was not much push in the open source world. Recently, the idea of DevOps or Ops 2.0 is gaining ground. We are starting to think of our deployment and provisioning methods more like software engineers. We are developing tools to help us provision

Scripting & Automation: The Qualitative to Quantitative Workflow

Background Scripting & Automation has been a goal since the beginning of Unix and, let me state, that I believe that it is possible to achieve a Fully Automated Provisioning system in our production environments. In fact, I think it is essential that we develop fully automated provisioning systems to keep up with the rate

We have moved: opensource.eyemg.com becomes crunchtools.com

Hello Everyone, I am proud to announce that http://opensource.eyemg.com has officially become part of http://crunchtools.com. When the original open source site was created, it was to facilitate distribution of open source software which had been developed in and around EYEMG’s data ceter. Since then the content has expanded to include a vision of tutorials, software

Browser & Web Server Cache Control Headers 101

Background Caching between a browser and an origin server is controlled by request and response headers . Quite often these headers are misunderstood by users and business owners, so it is important that we as systems administrators and developers understand them well. Secondly, caching can have an impact on web site performance and bandwidth usage.

Browser & Web Server Headers 101

Background Understanding the basic interaction between a web server and a web browser is critical for a beginning systems administrator or web developer. Basically, text is sent back and forth in a way that is specified by the HTTP protocol. Several versions of the protocol exist, but the details are not required to understand the