March 26, 2012
I can think of at least a dozen applications for this little Linux-based computer, and I just can’t believe the price!
RaspberryPi.org’s download page, linking the various distros
Raspbian, Debian Linux for Raspberry
Hexxeh’s Raspbian Image, CLI by default, but it has issues booting
Arch Linux, ARM version downloadable from RaspberryPi.org
Projects & How To’s
RPi Easy SD Card Setup, elinux.org
Running the Raspberry Pi headless with Debian Linux, Penguin Tutor
How to Turn a Raspberry Pi into a Low-Power Network Storage Device, How-To Geek
How to Build an All-In-One Retro Game Console for $35, the Easy Way, Lifehacker
16×2 LCD Module Control Using Python
Unlocking your new Raspberry PI’s 512MB of Memory!, HubCityLabs, a fix for an initial RevB problem
Add a 9-pin Serial Port to Your Raspberry Pi in 10 Minutes, David Hunt
Easy Raspberry Pi Based Screensaver/Slideshow for Exhibitions/Store Front, Instructables, a feh-based solution
A Month With Raspbian
Build your own supercomputer out of Raspberry Pi boards, ZDNet, a Beowulf Cluster story
August 13, 2011
Once upon a time, I had the need to make ethernet cables as a part of my job, crimping the little plastic connectors on the ends of bulk Cat 5 cable. I no longer work in this area of information technology, but I’ve recently found it necessary to renew and extend my knowledge if network cabling for other reasons. Here are some handy resources and notes.
RJ stands for “Registered Jack” and the succeeding number designates the standard wiring pattern used (a.k.a. pinout). Despite popular demand, this designation does not refer to the physical jack or connector. The connectors are actually named for the number of positions and conductors. For example, RJ-45 cables used for data networking use an 8P8C connector, whereas RJ-45 cables once used for telephony used an 8P2C connector. Similarly, wall-to-phone cables are either RJ-11 or RJ-14, which use 6P2C and 6P4C connectors respectively; the former has only one pair of wires to support one phone line and the other has two pair to support two lines.
Unshielded, twisted-pair (UTP) cable is categorized based on its physical properties. The main practical difference is speed. Cat 3 is used for telephony and 10BASE-T networking, Cat 5 can support 100BASE-T, 5e can support 1000BASE-T (Gigabit), and Cat 6 supports 10GBASE-T.
Cat 6 may include a better grade of wire than Cat 5, but the performance increase results primarily from improved insulation; thus, the connectors must accomodate the larger jackets or performance may be degraded due to poor assembly.
I’m not going to memorize these, so a good reference is always welcome.
Telephony. The colors of the wires for positions 1-6 are W/G,W/O,Bl,W/Bl,O,G. RJ-11 uses only conductors on positions 3 & 4, RJ-14 add positions 2 & 5, and RJ-25 use all six. The old colors are W,Bk,R,G,Y,Bl. Wikipedia has a very good table detailing these pinouts.
Ethernet. Ethernet follows the TIA/EIA-568 standards, either “A” or “B”. The order of the colors is different, but the order of the pairs is identical. [I’ve always seen T568A, but then, it’s not like I look at the pinouts on network cables every day.] For T568A, the colors for positions 1-8 are W/G,G,W/O,Bl,W/Bl,O,W/Br,Br; for T568B, swap all of the greens for oranges in the list above. Again, Wikipedia has a very good table for detailing these pinouts.
The Best Wiring Diagrams
Good pictures are always better – or at least quicker – to use than to have to decipher the orders of wires above. The best wiring diagrams I’ve found for wiring the more popular male connectors are published by Huffman Reference Materials. They even offer free PDF downloads showing the pinouts for several RJs on 6PXC and 8P8C connectors.
The diagrams on Project Resource Solution’s website are also very clear.
April 17, 2011
Back to My Lists
I recently, at the time of this writing, have obtained a Neoware CA19 thin client from a friend in whose garage it had been collecting dust. I’ve always been interested in the thin client architecture, but have never seen an implementation outside of one local library. Here, I collect links and notes to information about Neoware thin clinets in general.
The naming conventions for CA19 specifically and some good modding advice.
Much more to come…
June 28, 2010
When I finally committed to using Linux exclusively for my personal computing, I had just bought a new laptop and installed Ubuntu over the existing Windows partition. I removed the Windows badge from its place near the keyboard, but felt like something was missing. I looked online for Linux badges and found several listings on eBay. The best were from a shop called Funkyputers. I bought a lot of ten, including some bearing the logos of other distributions, just in case I decided not to stick with Ubuntu. The quality wasn’t quite as good as the labels stamped for manufacturers, but they’ve lasted surprising long without much fading. After running across a half-page ad that was shipped with my order, I thought I might order some new badges for the family’s new netbooks, only to find that Funkyputers is no more.
Contact info for Funkyputers included:
- 9 Cranbrook Street, Cardiff CF244AL, UK
I believe this was a sole proprietorship owned by one Tausif “Puck” Rahman. He’s the fellow that handled my order, and after looking up the company’s mailing address on Google Maps, it looks like it was probably run out of someone’s flat in Cardiff, in southern Wales. Puck seemed like a very nice fellow and I hope all is well with him.
August 30, 2010. I was recently contacted by one of Puck’s business associates as a result of this post. It seems that his decision to close shop was sudden and may have been motivated, at least in part, by personal circumstances. Whereas my correspondance with Puck was very brief, this particular customer had an ongoing business relationship with Puck and was able to determine that Puck was ok. He also recommended ScotGold Products in Aberdeenshire, Scotland for similar products. I’ve not had a need to shop there myself yet, but I’ll certainly give them a try when such a need arises.
December 31, 2009
The Beowulf Cluster is one of the reasons I jumped onto the Linux bandwagon in the late 1990s. The idea of making good use of old computers to solve real world problems fascinated me. As computers continue to shrink in size, price, and power consumption, the reuse aspect is less appealing than before, but the concept still draws me in from time to time. I only wish I could justify the cost of building one.
A Beowulf Cluster generally refers to a collection of consumer-grade computers connected by a local network that run parallel-processing applications. The typical Beowulf Cluster runs on the Linux OS and distributes processing tasks using either Message Passing Interface (MPI) or Parallel Virtual Machine (PVM) libraries.
- Wikipedia articles for Beaowulf Cluster, MPI, and PVM
- Beowulf.org FAQ and mailing list archives (1997-current)
- Some notes on how to build a Linux cluster by Guillaume and/or Jennifer Dargaud, 2003
How To Build A Cluster
Building the cluster is half the battle (the other half is writing programs for it). Thankfully, there are a lot of how-to pages out there. Some cover just the basic steps while others provide more explanation and background information. It’s been interesting to watch them evolve over time to, in length, complexity, and style. Here is a sample:
- Building Your Own Beowulf Cluster by David H. M. Spector, Wired, 2000
- Building Linux Beowulf Clusters by Mike Perry, fscked.org, 2000
- How to Build a Beowulf Linux Cluster The Mississippi Center for Supercomputing Research, 2001
- Sun™ Based Beowulf Cluster by Börje Lindh, Sun Microsystems, 2002
- The Beowulf HOWTO by Kurt Swendson, 2004
- Engineering a Beowulf-style Compute Cluster by Robert G. Brown, Duke University, 2004
- Building a Beowulf System by Jan Lindheim, Caltech, 2005 (last entry on Internet Archive)
- Beowulf Cluster Design and Setup by Amit Jain, Boise State University, 2006
- Building a Beowulf Cluster in just 13 steps by Sanath Kumar, Linux.com, 2009
- Building a simple Beowulf cluster with Ubuntu by Serrano Pereira, University of York, 2013
Finally, this isn’t a how-to article, but it’s worth the read. Cluster Urban Legends: Build Your Cluster With Facts Not Fiction, written by Dr. Douglas Eadline in 2007, debunks some of the major myths and misunderstandings surround Beowulf Clusters. In short, it helps you determine if you are really building one for the right reasons.
So, you’ve built a Beowulf Cluster. Now what? Well, now You have to write programs for your cluster to solve all of the world’s complex problems. Beowulf Clusters are built for crunching numbers, not serving up web pages. That means they are used primarily in the sciences, though I can think of a few business applications that could benefit from the extra processing power (think derivatives pricing).
I have a lot more research to do in this area. Currently, I have only a link to some information about an old text book to offer. I need to add more tutorials to this list, especially in the use of MPI and PVM, and how to determine when it’s appropriate to use one over the other. Check back later or watch my Twitter feed for updates.
- Designing and Building Parallel Programs by Ian Foster, Addison-Wesley, 1995
Real World Beowulf Clusters
Years ago, I started compiling a list of real Beowulf Clusters that had been built for various purposes. I still have the list, though some of the links are now gone or only available on the Wayback Machine Internet Archive. I was hoping to do a little write-up on each cluster on the list, but if that doesn’t pan out, then will just add the list in this section.
And of course, most scientists, engineers, and computer geeks are gifted with a great sense of humor (even if we are the only ones that understand our own jokes).
July 20, 2009
The Zen media player by Creative Labs seems to be a bit picky about the video formats it plays. After a lot of experimentation and little success, I eventually found the ZEN / ZEN Vision Series Video Encoding Guidelines. When I have time to play with it again, I plan to add to this post the methods that work best for me.
June 29, 2008
Here’s my thoughts on a Linux-based headless web client:
- MiniKnoppix would be a good platform, but the following packages would have to be readded: anacron, expect, html2text, m4, ndiswrapper.
- Knoppix has a “persistent home” option.
- The JFFS filesystem will distribute wear on a Compact Flash drive.
- Fetchmail & procmail could be used to retreive simple text info by cell phone or IM.
- “Web Client Programming with Perl” & “Spidering Hacks” by O’Reilly publishing would provide much help in scripting scrapes and other tools/toys.
February 18, 2008
At the time of this writing, many laptops, including Dell and HP/Compaq, contain Wifi cards made by Broadcom. In the past, there has been no ‘official’ driver written by Broadcom for these devices for Linux. A tried and true way of using these cards with Linux is through the use of the NDISwrapper utility.
- Install NDISwrapper package if not already installed.
- Download the Wifi drivers from Dell, Compaq, etc.
- Extract the necessary files (e.g. bcmwl5.inf & bcmwl.sys). This may require running a “self-extracting” file under Wine.
- Install the driver: sudo ndiswrapper -i /dir_path/bcmwl5.inf
- Verify the hardware is present: sudo ndiswrapper -l
- Load the driver: sudo modprobe ndiswrapper
- Update the configuration: sudo ndiswrapper -m
- NDISwrapper homepage: http://ndiswrapper.sourceforge.net/
- NDISwrapper manpage: http://linux.die.net/man/8/ndiswrapper
- Another copy of these instructions: https://www.scientificlinux.org/documentation/howto/ndiswrapper.broadcom