Microsoft Baseline Security Analyzer Troubleshooting

Microsoft Baseline Security Analyzer (MBSA) is a useful tool for auditing the configuration and update status of Windows computers. Most of the time, its reports are useful and easy to understand. However, some of its responses are baffling, and some of its suggested solutions haven't been updated since Server 2003. Here is my collection of … Continue reading Microsoft Baseline Security Analyzer Troubleshooting

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Troubleshooting SSSD, realm, kerberos, and SSH

SSSD (System Security Services Daemon) allows Linux systems (specifically, Red Hat, CentOS, and Fedora) to verify identity and authenticate against remote resources. If you have a CentOS or Red Hat enterprise system, and you need to authenticate against a domain controller such as FreeIPA or Active Directory, SSSD is the way to go. I use … Continue reading Troubleshooting SSSD, realm, kerberos, and SSH

LVM device-mapper: reload ioctl failed: Invalid argument

LVM2 (Logical Volume Management) is pretty amazing, but when something goes wrong, it's not easy to troubleshoot. This is not the fault of the tools, but a reflection that LVM is relatively new in Linux, and not widely understood. What I Tried to Do I tried to increase the size of a logical volume with the lvextend … Continue reading LVM device-mapper: reload ioctl failed: Invalid argument

Is it worthwhile to embed structured data in Web content?

Short answer: not really! A few years ago, I was fascinated with the idea of microformats. The concept is to add structural data to common HTML tags so that certain types of data on a web page can be clearly identified. Adding structural information makes it easier to automate the parsing and indexing of web content. The original microformats … Continue reading Is it worthwhile to embed structured data in Web content?

Monitoring with SNMP, Part 3: Automate active monitoring with Nagios

My last post showed how to monitor networked devices with SNMP. You could try to remember to manually check the status of things periodically, but that would be missing the point of computers. Instead, automate your monitoring with Nagios, a web-based monitoring tool for Linux that automates the process of actively querying devices and doing … Continue reading Monitoring with SNMP, Part 3: Automate active monitoring with Nagios

Monitoring with SNMP, Part 2: Command-line tools for active SNMP

In Part 1, I summarized the basic concepts of SNMP and defined the terms and acronyms used in this post. Now, I will show how to use SNMP to monitor actual devices. As an example, I will monitor an enterprise-grade uninterruptible power supply (UPS) and power distribution unit (PDUs) from Tripp-Lite. These devices have an … Continue reading Monitoring with SNMP, Part 2: Command-line tools for active SNMP

Monitoring with SNMP, Part 1: Fundamentals of SNMP

SNMP is a protocol for conveying information and controlling devices over a network. SNMP can be used in two ways: Active: a device sends a command to set a parameter or request information for another device Passive: a device sends an alert (called a trap) to another device, which is configured to receive traps and … Continue reading Monitoring with SNMP, Part 1: Fundamentals of SNMP

“Exporting” a project from a Git repository

What do you do when you want to distribute or release source code that is stored in a Git repository? Obviously, if your target audience is using Git, you can just compress the directory that contains the repository and distribute the copies, or give the users a way to clone your repository (such as GitHub). … Continue reading “Exporting” a project from a Git repository

Running network experiments on the GENI project

The GENI Project is a networking testbed that is used by researchers studying novel networking technologies. While the technology is fascinating, the web site is, unfortunately, a confusing mess. Here are some pointers to get you started (or refresh your memory). This post will be updated as I learn more. Key GENI Links GENI Portal … Continue reading Running network experiments on the GENI project

Collaborative Git workflow: Shared Repository on a File Server

GitHub is a great tool for collaborating on projects. However, sometimes it is necessary to mimic the "GitHub workflow" using a shared repository on a local Linux server. The following example shows how I shared an example repository with multiple users.  We are also using the Git flow model for branching, aided by the handy … Continue reading Collaborative Git workflow: Shared Repository on a File Server