A Fishy Solution

Monday, June 25, 2012

I had an odd problem adding a new disk into my MD raid set - it is an identical drive to the other 5 drives already in the raid set, but it could not be added, citing the disk being a bit too small to add to the array.

I was able to debug the issue succesfully with Tuna, a project that I am working on at Red Hat intended for RHEL7 that gives a simple interface to modifying kernel parameters, looking at kernel devices, processes, etc; generally exposing parts of the kernel to make system tuning easier.

https://gist.github.com/2974057

With my new storage-support add-in, it became immediately clear why this drive was "different" than the other ones; it was sitting on a different controller. Further examination revealed that this controller reported the drive with a rather different drive geometry that resulted in the loss of a few megabytes of space. It was also immediately clear an easy solution: I simply had to switch my plugs on my CD-drive (/dev/sr0) with the new drive. Sure enough, it added to the array just fine after that.

Some people use raid on top of partitions slightly smaller than their drives to alleviate the possibility of this problem from happening; in this case, I don't think that is really necessary; two of the three controllers in this server work perfectly correctly/sanely with the drives, it is only my LSI Logic / Symbios Logic SAS1064ET PCI-Express Fusion-MPT SAS (rev 08) that does not deal with these 3TB drives very well, or at least in a way maximally compatible with other controllers.

I'm happy the software I'm currently writing is useful in real-life server debugging problems :-) In fact, it would have been very difficult to debug with other disk-administration software, as many of these sit at a much higher logical level than direct kernel interaction.

Categories: Red Hat

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AMD Graphics + Runaway: A Road Adventure

Wednesday, December 28, 2011

If you're experiencing graphical issues with the adventure game Runaway: A Road Aventure, I found an issue with AMD's anti-aliasing support. The game performs it's own antialiasing, and the morphological filtering anti-aliasing setting, as set in the Catalyst Control Center's "3D Application Settings" will have to be disabled, else a very interesting but unplayable situation happens where every game screen refresh, the game performs its own antialiasing, and in the subsequent frames AMD's own antialiasing kicks in and proceeds to blur further and further until the next time the game redraws the screen itself, whereupon for a single frame everything is perfect, but things quickly blur farther and farther from there, as the anti-aliasing function is continiously re-applied to the same buffer.

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A Well-Oiled Machine

Friday, December 16, 2011

In case you're wondering what the maximum amount of motor oil in your basement that can drip into the RAM banks of your Itanium2 with a lot of registered ECC DDR dimms, it's about this much:

There were other slightly less lubricated DIMMs in the server that continued to operate fine; this amount appears to be near the upper ceiling for RAM lubrication.

The more you know!

As a testement to enterprise stability, the machine operated just fine through the ordeal, albeit it stopped using 4GB out of the 12GB of RAM on board until I gave the motherboard and RAM a good ol' degreasing.

Only one DIMM actually was permanently damaged as a result of the ordeal; the rest have been put back into service.

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Wireless Network Scanning in Windows 8

Sunday, December 11, 2011

Aren't I great at Windows scripting? (Sarcasm)

[11/12/2011 - 00:36.51] ~
[clockfort.clocktop] $ netsh wlan show all | grep Channel | sed -e 's/.*: //g' | sort -n | uniq
1
6
10
11
52
56
60
64
132
153
157
161

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Project Yodel Toaster

Wednesday, August 10, 2011

There's an older video game named Spelunx, a kind of kid-oriented Myst-style game with worse graphics, made by the same company that put out Myst, Cyan.

A notable feature in the extremely-hidden backstory of this game, is an in-game book, a key plot point of which is a royal decree issued for persons everywhere to construct the very best yodeling toaster in the kingdom.

Given the lack of competition in this area, I believe I should be declared the de-facto winner of this particular competition :-) And yes, it still toasts.

WARNING: Toasters operate directly on mains/line power, and can get very hot. This isn't just a standard disclaimer, toasters (at least my cheap GeneriBrand NoSafetyOversight Edition) are apparently not expected to be reparable/openable and contain exteremely dangerous circuitry. The main toast lever on my model presses down on a quarter-inch by 3-inch thin strip of bendable copper that makes contact with another static copper contact farther down when depressed. This huge unexposed strip was, of course, line power, which was just applied to the heating coils whenever they needed to be heating. The timer functionality was implemented mechanically. So simple. So cheap. So dangerous to work around with the power on while testing your half-assembled yodel toaster.


The Willing Victim


On a related note, I cannot confirm or deny that the table below is being held up by a soda bottle, nor that the table in question is actually a door.


Parts/Tools Used


  • Small phillips screwdriver
  • Angle Grinder (seriously)
  • Old 5V wallwart
  • Audio-playing electronics
  • Sheet Metal (I used a spare breadboard backing plate)

Creation of an Electronic Audio Solution


I was originally going to put in a tiny AVR and bit-bang out the audio into a PC speaker, but the amount of flash on the microcontrollers I had was prohibitively small for storing sound samples, even with a few space-saving tricks. The off-the-shelf solution was like $8 from an online electronics place (google 'diy audio greeting card' or similar to get several different models/suggestions), so I had no problem going with that.


Disassembly of the Toaster's Plastic Housing


This toaster was easy to disassemble, as if the manufacturer was secretly encouraging yodel-based modifications, with normal phillips screws on the bottom holding a few plastic outer shell parts together. The only unusual part was how they all snapped together and how the plastic lever extension had to be removed first before continuing disassembly. While performing this step, look for areas of open space that will be A) Not excessively warm during device operations and B) Enough space to fit your electronics guts.


Making The Parts Fit


YMMV; this step will obviously vary wildly or may be completely optional with differing base toaster models.

Keep in mind when performing modifications that you won't want your poor PCB getting too warm during Normal Toasting Operations (NTOs).

Toaster innards

Toaster, incision sites marked and ready for surgeon

The surgeon delicately performing the operation on the patient with an angle grinder


Addition of Audio Circuitry


Find a nice way to mount your electronics guts into the chassis. Try not to short it out on the metal heat shield, and try not accidentally desolder the PCB during NTO.

In order to make a clean looking single-power-cord going into the device, with no external signs of yodel-capabilities, I fished a spare 5V-DC wallwart out of my housemate's Box-O-Extra-Wallwarts(TM), and integrated this into the device.


Addition/Integration of Button Circuitry


I confess I have not taken apart any toasters besides this one, so do not consider me a subject matter expert. In my particular model, as described in the warnings section, the lever just presses a strip of wire connected directly to mains down to make contact with the resistive heating circuit. I really hope this isn't how they all do it, that's gross.

Anyways, you should either somehow latch onto whatever contact they have, make your own contact that triggers when the button is pressed and/or comes up after finishing a toast action. Having the depress-action (falling edge) also resulting in a yodel gives the added benefit of alerting you that your toast is complete! In my case the toaster did not have a bell for this functionality like others might, so this was a welcome feature to have.

In my case, I ended up cutting a small piece of sheet metal from a spare breadboard backing and very carefully folding it, which was actually a joy to work with, even given the small size of the mechanical/electrical contact I was extending. I then wired this up along with a matching contact to form a press-button circuit to my electronics.

Categories: Projects

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DEFCON 19 Badge Puzzle: PDP-8 Assembly

Wednesday, August 10, 2011

According to contest creators, the last part of the message (the text after the ::) on the badge is meant to be PDP-8 instructions. Ignoring the last character of the one-bit-extra first four groups (which encodes ['1', 'o','5','7'] , representing the name of the contest's creator Ryan "1o57" Clark) of these pairs, we have:

101010001000

111010000000

001010010011

111100000010

000000000000

000000000000

000000000000

This, as far as I can tell, translates into:

JMP 8

CLA

TAD 19

HLT

... and the all-zeroes sequences that follow could /technically/ be ANDing the AC with zero, but, they're after the halt, and zeroed out memory tends not to really mean much in a more sane context.

But, these instructions don't really make too much sense. Why would someone program this? Did they make a typo with the JMP 8?

Very odd.

Categories: Projects

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Custom Messages in QR Codes

Sunday, June 19, 2011

QR code featuring CSH logo

QR codes are cool! The Reed-Solomon coding for error correction in them can be fairly robust, and given the appropriate QR-code format settings, enough to push in plenty of invalid (but aesthetically pleasing!) data.

I whipped one up for Computer Science House, pointing at our website and containing our logo (or, at least, my 8x8 pixel re-imagining of the logo). A slightly larger logo could be accommodated via the generation of a secondary URL for the purposes of manipulation of the raw QR code image (i.e. something akin to example.com/redirect/a6p356adfaa, which could /then/ link to csh.rit.edu in a redirect).

With this, one could theoretically generate a QR code with la large amount of bit-overlap with a logo, thus minimizing the amount that error correction has to make up for. However, the math for this is.... complex. I suppose one could easily attempt a brute-force strings-generation while generating qr-codes, and keep the one generated with the most overlap, but I have not calculated the scope of this problem, thus not having determined its feasibility.

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Functionally Awesome

Tuesday, April 19, 2011

I've been pretty swamped with work lately, but I've found time to start doing Project Euler problems, which are pretty fun to solve. I've completed 16 of them today! It's a pretty great way to exercise my mind with new ways of thinking, and it's quite excellent for learning/practicing Haskell. Plus, I gave the bug to my buddy Alex Grant, who is currently catching up to me on Euler problems, in a vague attempt to prove that Ruby is just as valuable a language for this sort of programming problem, as well as having a lot of fun himself. I may have lost him with the release of Portal 2 though... oh well, he'll be back. :-)

I've been on a weird Haskell kick recently, and I gave an intro presentation on the language for BarCamp Rochester 2011, and it was well-received. Other than learning new things and doing considerably more math-for-fun than I'm used to, life has been pretty good. I also have a trivia-solving piece of software in the works, and I'm pleased with the performance it has so far. Hopefully I'll finish and unveil it by this year's Innovation and Creativity Festival at the Rochester Institute of Technology!

Categories: Projects

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Book Review: Security Warrior

Saturday, March 12, 2011

Cover of Security Warrior book

Security Warrior by Cyrus Peikari and Anton Chuvakin

ISBN: 9780596005450

This book is an excellent introduction into the world of computer security. I was a bit surprised at the contents; the book features many more offensive techniques, like reverse engineering binaries, performing successful stack/heap overflows, attacks on a variety of server/network platforms, and defeating IDS/forensic technologies. I had initially expected the book to be more focused on security defense, which is covered, but certainly not in a typical ratio. I wouldn't complain though, because as is stated in this book several times, a good offense is a good defense. For instance, upon introducing stack overflows, the authors wisely quip how a company could save a great deal of money and embarrassment if its employees found such vulnerabilities before they leak into the wild.

If I did have one bad thing to say about Security Warrior, it's that I happen to know quite a bit about its entire first section already, so I found parts quite tiresome. Having already read such texts as Chris Eagle's "The Ida Pro Book", this book's section on disassembly seemed a paltry introduction in comparison; however, it seems this amount would be about right to gently introduce someone to the subject, were they not already aware of this field of computer security knowledge.

All in all, Security Warrior is a good introductory text to a wide variety of computer security related topics, and hopefully the reader will leave interested in implementing at least a few of the defensive strategies listed, or want to become more familiar with some of the more interesting attack vectors. Further reading/knowledge will be needed other than the information found here in order to do useful security work, but, Security Warrior certainly at least gets the ball rolling and the interest piqued.

Categories: Book Reviews

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Backup Software Cache Management

Monday, May 24, 2010

So, normally, backup software is going to read 90+% of your machine's hard drive, and push that data over the network to someplace else.

However, in the process of doing this, it is going to steamroll your operating system's filesystem cache.

There are two improvements that can be had here, in my reckoning, and I've seen neither in implementation.

1) Have the backup software back up the files that are in the operating system's cache FIRST. Not only does this mean that important, often-changed files get priority, it means that backups will be slightly faster, as this data will come from memory, rather than from the disk.

This would probably require some way of getting at a list of what files the kernel/caching-daemon/whatever has in memory, which I'm not sure exists at the moment.

2) Have the backup software use a different way of accessing the disk such that the file caching daemon does not cache the files that the backup software is reading. This way, rather than steamrolling over the carefully-laid out filesystem cache of the system's most often and/or most recently used files, the uncommon never-accessed-normally files don't suddenly get pushed into filesystem cache when the backup software accesses them. This would lead to general system speedup, as "better" files from disk would be cached, rather than rarely-used junk.

This could be as simple as adding an oflag option to the kernel (i.e. fcntl.h in linux) that says "don't cache this please", and then using this when calling the open function in the backup application.

... Just some musings I had while talking to Russ on our way driving to California.

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