Planet PLUG

A very useful mail gateway setup on Linux to be an edge server for MS Exchange.

Set Up an Email Gateway with CentOS Linux�5.4 � Aaron Walrath – Another IT Guy's Meanderings

I finished a quarter wave dipole antenna yesterday, and had a chance to try it out tonight.  I wasn’t able to get a signal report (I tested at 1am), but I definitely was able to get into several Philadelphia 440Mhz repeaters.  This is neat to me because the antenna is so simple, yet already is showing better performance than a commercial mag mount antenna I have.

I made the antenna such that it can easily be taken apart.  This way, it can be moved without the high probability that it would be damaged.  Please see the pictures.

I know there are some other cyclists in the GNOME community who are probably bummed that they’re spending a week away from their bikes, so if anyone else is feeling withdraw symptoms from not riding I am planning to find a bike shop in Den Haag where I can rent a road bike and do some early morning rides before guadec starts. If you’re interested in some early morning pain and suffering grab me at guadec and let’s figure out a route.

Alright, so it’s been done for 9 days now, and I’m just now getting around to making a blog post about it, but I have a working SD card writer.  Basically, I took an existing example (that came from Ryan Owens (Spark Fun) using a library written by Roland Riegel) and modified it to be a log file generator.  It works on the MicroSD Shield, http://www.sparkfun.com/commerce/product_info.php?products_id=9802.  I hope to roll this into a library set of it’s own soon, so my program will reflect “initialize_log” and “write_to_log” functionality.  Fun fun!

One minor issue with EC2 is that they supply the kernel, and that already caused difficulties with my first EC2 tutorial – the image I created doesn’t let you create a new snapshot from a running image since the EC2 kernel lacks loopback support, and I didn’t supply a matching kernel module.

Amazon has a nice guide on how to do it – here is a gentoo-specific one.

These instructions start from a working ami image created using my previous instructions. Go ahead and mount it and chroot into the image.

1. Install a kernel using emerge xen-sources
2. Be sure to enable xen support in the kernel config file. Here is a working config.
3. Build the kernel with make && make modules_install as usual
4. Copy the kernel image to /boot as usual.
5. Create /boot/grub/menu.lst, containing:
   default 0
timeout 3
title EC2
root (hd0)
kernel /boot/kernel root=/dev/sda1

6. While optional you might want to clean up the kernel source directory, or even remove it – you’re paying by the gb and the sources and object files are large.
7. Bundle it up with the instructions in the first guide, but on the ec2-bundle-vol command line add –kernel followed by a suitable kernel ID from the pdf linked above. For a 64-bit ami in the US-east region use aki‐427d952b

That’s it – upload, register, and boot it up!

I registered a public ami at ami-bcf11ad5, which you can feel free to take a look at. xen-sources is running a fairly ancient kernel on stable – maybe on a later installment I’ll look to update that.

Additional note: I registered a public ami at ami-8f04efe6 which is running 2.6.34 on a 32-bit gentoo install. It also is running the latest stable udev.

On both images I have an entry in root’s ssh authorized_keys so that I can more conveniently access these instances when I’m using them. If you use this for anything other than experimentation you should remove this before creating your image. I’d host a version with and without this, but that does cost money on S3, so consider yourself warned…

Filed under: gentoo

I always find great stuff on the emacs-fu blog but today I read a particularly-wonderful post about Emacs keyboard macros. Like the author, I’ve been a long-time Emacs user but never really got into keyboard macros because it’s been quite easy to produce an elisp one-liner in many cases. That being said, this seems like a great time to learn so I look forward to reading more on the topic of keyboard macros as well as learning some new tricks.

Thanks for a great post!

Dear Dutch foss community,

A friend and I are attending GUADEC this year, but we have plane tickets to fly into Amsterdam on the 24th of July. The problem? GUADEC isn’t until the 26th! Neither of us have ever been to Holland, and while 2 days is certainly not enough time to enjoy Amsterdam, we want to try. If anyone has a bed/couch/floor/stable/etc. that the two of us could sleep in/on/under the night of the 24th we’d be super appreciative, and of course you’d always have a place to stay wherever it is that I’m living when you need a place to stay (at the moment Philadelphia- a really great town if you want to come visit, seriously Philly rules!).

Of course we’ll take you out, or cook you a nice dinner in return for your hospitality, and promise not to make a mess.

If you have a floor or whatever that we can sleep on, feel free to either leave a comment or send me an email alex.launi@gmail.com!

The first hit I received when I searched for “Arduino Mandriva” was http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1259672641/2.  For some reason, wget failed on me when I followed the listed directions.  Instead, I just downloaded arduino-0018 and avr-* from ftp://blogdrake.serveftp.net/mandriva/2010.0/free/i586/ and avr-libc from ftp://blogdrake.serveftp.net/mandriva/2010.0/free/noarch/ to a local directory.  I then added that directory to my list of repositories (custom – local file).  For some odd reason I need to run it with root permissions to get serial port access, but it works.

I’ll note I tried this because the source from the Arduino website didn’t work out of the box, dependency issues.

“A high fidelity ungrounded torque feedback device: The iTorqU 2.0″
15 full-text downloads between 2010-06-10 and 2010-07-02
102 full-text downloads since date of posting (2009-06-29)
Congratulations! This paper has now been downloaded over 100 times!

To encourage readership, simply refer people to the following web address:
http://repository.upenn.edu/ese_papers/497

A friend of mine presented his research from the past few months at the lab’s weekly meeting today.  He used Beamer/LaTeX to create his slide show.  I’m a fan of TeX, so I was impressed.  I was more impressed when I came to learn that he used pgfplots to make his figures, rather than Matlab.  Check out pgfplots at http://sourceforge.net/projects/pgfplots/.  I want to point out that he simply exported his data (from Matlab, but he could have used Octave) to a csv file.  He then made his plots within LaTeX so that he had ultimate control over the plots, and they really did come out nice.  I thought eps (vector graphic) figures trumped jpgs (read as LaTeX trumps PowerPoint for science slides), but I’m excited to say that pgfplots trumps eps (which still reads as LaTeX trumps PowerPoint).

I’m starting to think that I might need to do a short presentation on LaTeX for my local LUG; they (we) have been desperately looking for presenters on Linux-ey topics.  Maybe in another two or three months, after I get another paper or two at least submitted to a journal/conference.

I can’t post a link to the article, since it’s not yet available at linuxjournal.com, but this month’s LJ issue just happens to cover the Arduino board!  They cover plotting data using the Arduino debug serial command and kst.  Very cool.

My mentee has just finished the wiring harness for all of our analog sensors (six in total).  He’s working on placement of the sensors and plotting some of that data this weekend (though not with kst).  I’ve started delving into the mp3 shield we got from sparkfun.com, and hope to get that working with the microsd card shield this weekend.  I had to relocate the chip select (CS) pin on the lcd shield we have, as it interfered with the cable select for the mp3 player.  It looks as if the MOSI/MISO pins can all be shared between the shields, so long as the cable select is activated before data is sent to the corresponding shield.  Neat.