Author Archives: Daniel Feldman

Remote graphical access to Unix machines

By Daniel Feldman | Published: March 2, 2011
As far as I can tell, these are the options: The venerable VNC, which basically compresses a screenshot of the entire desktop over and over again and is consequently pretty laggy. The project has forked into RealVNC, TightVNC, and UltraVNC, all of which are more or less interoperable. Straight X11 protocol over SSH, which is [...]
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What’s the difference between spot and on-demand EC2 instances?

By Daniel Feldman | Published: February 28, 2011
EC2 allows you to rent VPS instances by the hour at either a high fixed rate (called “on-demand” instances) or a much lower rate determined by auction that comes with fewer features (called “spot” instances). However, Amazon’s documentation is horribly obfuscatory when it comes to which features you’re giving up by going with spot instances. [...]
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PCA of test scores

By Daniel Feldman | Published: February 25, 2011
Here’s a principal component analysis biplot of test scores in a class I’m TAing: The test had 15 problems. Each dot represents one student score, while the 15 vectors starting with V are problems on the test rotated into the coordinate system defined by the principal components. Better scores are in the top-left (signs are [...]
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Google Talk + Acer 1410 + Linux = problems

By Daniel Feldman | Published: January 16, 2011
Some HDA sound chips, eg. the one in my laptop (Intel 82801I in my Acer 1410), report that they have a single 2-channel audio input when they really have 2 1-channel inputs (a microphone and a mono input jack). This kind of thing can sometimes be fixed by playing with audio profiles or passing different [...]
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Trac shows blank page in Chrome

By Daniel Feldman | Published: January 3, 2011
I use the excellent Trac project management system to host a couple of small projects. For as long as I’ve been using Trac, Chrome and Safari users sometimes get a completely blank page where Trac should appear. I had just been telling them to use Firefox or IE, but I decided to get to the bottom [...]
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On securing web apps

By Daniel Feldman | Published: December 15, 2010
I recently wrote a little to-do list/time manager app using jQuery. I was impressed at how easy it was to put together this app quickly — I had it done in a weekend, with multiple menus, some custom widgets, about 10 different JSON calls, etc. I’m thinking about taking the app public, and since to-do [...]
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Startup Weekend

By Daniel Feldman | Published: November 22, 2010
Over the weekend I participated in Startup Weekend Twin Cities. If you’re not familiar with it, Startup Weekend attendees come up with the idea for an online venture on a Friday night, split into teams to carry out the best ideas over the weekend, and present their work in front of a panel of judges [...]
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