Distributed MySQL Sleuthing on the Wire

Intro Oftentimes you need to know what MySQL is doing right now and furthermore if you are handling heavy traffic you probably have multiple instances of it running across many nodes. I’m going to start by showing how to take a tcpdump capture on one node, a few ways to analyze that, and then go into how to take a distributed capture across many nodes for aggregate analysis. Taking the Capture The first thing you need to do is to take a capture of the interesting packets. [Read More]

Quick Tip: Dynamically Updating Screen Window Titles With The Current Server Hostname

I haven’t had a ton of time for blogging lately but figured this tip was good enough to throw out there for all the screen users. One way I like to organize servers that I’m ssh’d into is using screen windows. As you hopefully know you can use Ctrl-A c to create sub windows within screen. Then you can switch between them in several ways such as using Ctrl-A X where X is the window number, Ctrl-A n or Ctrl-A p for next and previous, and Ctrl-A “ to get a list of the windows for selection. [Read More]

Prevent SSH Attacks Using DenyHosts

Introduction If you have any servers that are running SSH and listening on a public net connection, its a good idea to prevent against dictionary attacks, since they are the simplest way to gain entry. You can get an idea of who is connecting or attempting to connect by viewing your ssh log which is located at /var/log/secure on Redhat or /var/log/auth.log on Debian. There is an easy tool that you can install to deal with this attack called DenyHosts. [Read More]