Feisty & rkhunter

It’s always good to do a regular rootkitcheckup on your system. A nice tool for doing so is rkhunter.

1.1) What is Rootkit Hunter?
Rootkit Hunter (RKH) is an easy-to-use tool which checks
computers running UNIX (clones) for the presence of rootkits
and other unwanted tools.
1.2) What are rootkits?
Most times they are self-hiding toolkits used by blackhats,
crackers and scriptkiddies, to avoid the eye of the sysadmin.

Continue reading “Feisty & rkhunter”

OpenWRT: ‘pushing’ the linksys wrtg54 on step further

A while back a wrote a small note about linux for embedded devices. Yesterday I put that to the test by installing OpenWRT on my Linksys WRTG (v2.2).

The installation was as smooth as ice: No problems at all! I first installed the latest stable. This was simply done by logging into the existing webinterface of my Linksys WRTG, and doing a firmware upgrade with the specific image for my linksys.

A note here: Read the common mistakes, like for instance this important one.

“You need to convert the bin (eg. openwrt-wrt54g-squashfs.bin) file to a trx file before reflashing” WRONG!!!

The openwrt-brcm-squashfs.trx is a generic trx file that will work on any supported broadcom platform. The openwrt-wrt54g-squashfs.bin is just “bin header + openwrt-brcm-squashfs.trx’, the bin header just contains the firmware version number and what models the firmware can be loaded on; the bin header is only used for verification before writing the trx data to the flash. The mtd utility writes the given file to flash without verifying it; use one of the openwrt-brcm-squashfs.trx when using mtd. Converting the openwrt-wrt54g-squashfs.bin file back to a trx is just plain ignorant.

Continue reading “OpenWRT: ‘pushing’ the linksys wrtg54 on step further”

ubuntu & xfce : setting your window size

What I hated was that when I opened up some new terminal windows that it left some space unused between the windows. Okay, there are some tiling windows managers, yet I still like the whole desktop feeling xfce gives me (without the resource bloat Gnome & Kde).

So I checked what size my terminal was when I had four of them open, and I set that value as their “startup size”. How can you do this?

xfce4-terminal –geometry 110×35

Original information found here.

Tuning Disks I/O for best performance

Read up on this article.

Learn more about direct I/O, concurrent I/O, asynchronous I/O, and best practices for each method of I/O implementation. This three-part series on the AIX® disk and I/O subsystem focuses on the challenges of optimizing disk I/O performance. While disk tuning is arguably less exciting than CPU or memory tuning, it is a crucial component in optimizing server performance. In fact, partly because disk I/O is your weakest subsystem link, you can do more to improve disk I/O performance than on any other subsystem.

Credits go to “Ken Milberg” on writing the article. I enjoyed reading it, as it was very interesting.

Grinder : Load Testing Framework

What is Grinder?

The Grinder is a Java load-testing framework. It is freely available under a BSD-style open-source license. The Grinder makes it easy to orchestrate the activities of a test script in many processes across many machines, using a graphical console application. Test scripts make use of client code embodied in Java plug-ins. Most users of The Grinder do not write plug-ins themselves, instead they use one of the supplied plug-ins. The Grinder comes with a mature plug-in for testing HTTP services, as well as a tool which allows HTTP scripts to be automatically recorded.

How can I use it? A small tutorial…
Continue reading “Grinder : Load Testing Framework”

Performance impact of the VmWare Virtual Switch

Let’s start out with the basics. Vmware has several products that can be used for virtualization. The most commonly know products are “vmware workstation”, “vmware server” & “vmware player”. They should actually be classed under “emulation” rather than device sharing. In my “hobby environment” I used the VmWare server; It’s free, and it’s solid.

Yet for the enterprise needs, esx is the way to go. Esx is a kernel on it’s own, and enables the virtual machines to really share the resources. This gives esx an extreme advantage over the other products, yet be aware that it also implies technical restrictions/difficulties.

As you can probably guess, adding an extra “emulation layer” will result in some performance loss. Those products will most likely suffice for function test/development environments. Yet a bit more performance and resource sharing is required for servers that need an enterprise production level.

Another thing you need to consider is infrastructure architecture you’re going to build. Here is where the article comes down to… The network sharing part in ALL vmware products is done thru a kind of “virtual switch”. This program is software, and is bound to cpu usage. When several servers share an environment within a vmware product, and one server starts to do a lot of bandwith. Then all servers will notice this as the virtual switch will need cpu power for this.

Don’t get me wrong here… I don’t want to bash the product, but I want to make you aware of this situation so that you can design your server farms for this.
For example: organise your farm so that the intensive servers share their environment with some “light” servers
Also make sure your system architectures know this limitation! This gives them the opportunity to design a system that suits a shared hosting environment. It’s just awfull if everybodies hard work goes down the drain, due to a design issue that could have been tackled.