IBM's Websphere MQ is a middle-ware application that allows two applications to pass messages back and forth without having to integrate with each-other directly. Websphere MQ is a fairly popular application in the enterprise especially for those running many java based programs.
Today's article is a copy of my personal Websphere MQ cheat sheet. This cheat sheet is geared more from a System Administrators prospective and doesn't touch much on creating or altering queues or channels, but should provide a good head start for those who need to just get something restarted.
When it comes to package management on Red Hat based systems Yum (Yellowdog Updater, Modified) is my preferred method. It's a quick and easy way of installing desired rpm's and their dependencies as Yum will automatically resolve dependencies before installation.
Most Red Hat base distributions include a public facing Yum repository that you can configure yum to use in order to save from having to maintain a local copy of every package on each system.
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.
Today's article may be pretty basic for regular readers but hopefully some may find it useful.
This article will cover creating a crontab entry and show some examples of common crontabs. The Cron daemon is a service that runs on all main distributions of Unix and Linux and specifically designed to execute commands at a given time. These jobs commonly refereed to as cronjobs are one of the essential tools in a Systems Administrators tool box.
In one of the first posts of this blog I covered some basic SystemTap functionality from an email that I sent to members of my team, but I have always felt that I haven't given SystemTap as thorough of an article as this incredible tool deserves. Today I want to correct that.
For today's article I will show how to compile SystemTap scripts on one server while running the compiled module on a production server without installing debug-info or devel packages in production.
For me when it comes to useful commands xargs ranks along side commands like find, top and df; xargs is a great time saver and incredibly useful. Today I will show a few examples of usage and some of the lesser known features.
Basic Usage The xargs command is used to take the output of one command and provide it as arguments to another.
# ls [0-9]-test.xml | xargs chmod -v 644 mode of `1-test.
Linux has many tools available for troubleshooting some are easy to use, some are more advanced.
I/O Wait is an issue that requires use of some of the more advanced tools as well as an advanced usage of some of the basic tools. The reason I/O Wait is difficult to troubleshoot is due to the fact that by default there are plenty of tools to tell you that your system is I/O bound, but not as many that can narrow the problem to a specific process or processes.
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.
Have you ever said to yourself, “man I really need to slow down my internet”?
Probably not very often, but recently I found myself in a dilemma where I needed to simulate 120ms of network latency in my test environment which consists of servers that are racked right next to each other. That is where the command tc comes in.
Within the current distributions of Linux there is a kernel component called netem, which adds Network Emulation and is used for testing and simulating the same types of issues one would see in a WAN (Wide Area Network).
Whenever I perform any type of activity that requires me to look at historical system statistics such as load average, CPU utilization, I/O wait state, or even memory usage; I usually skip the System Monitoring Applications like Nagios or Zenoss and start running the sar command. While I'm not saying that sar completely replaces those tools, I am saying that sar is quick and dirty and if all you want is some raw numbers from a certain time frame; sar is a great tool.