Log

In this register log I record things I’ve learned that I think are worth recording. These are generally problems with solutions that took me a while to find, often related to fixing some Linux issue.

October 28th, 2014

Finding the area under a curve with a spreadsheet program (Excel, Libreoffice Calc) or QtiPlot

For performing elemental analysis by x-ray photoelectron spectroscopy, I needed to integrate and find the area under the peaks in some spectra. One approach is to fit each peak with a Gaussian function and use the area of the Gaussian. For some convoluted peaks, I wanted something simpler. I wanted to get the total area under each peak without fitting it in any way. I use QtiPlot almost exclusively for plotting and fitting (fityk is my other go-to program) and one of the menu options for plots is Analysis->Integrate. That option brings up a tiny dialog where you can select…
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October 10th, 2014

Will that motorcycle pay for itself really?

In deciding whether or not purchasing a motorcycle is a prudent decision, cost plays a significant factor. Motorcycles often get much higher gas mileage (fuel efficiency) than cars. A common belief is that because of this fact, a motorcycle might pay for itself. I wanted to believe this is true, but after running the numbers, this belief is a myth and is only true in extreme circumstances. I’m recording the relevant equations here so that next time I get the impulse to by a motorcycle, I won’t use cost savings as a justification. In my situation, my everyday car, the…
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July 17th, 2014

How to align the red-green-blue (RGB) LCD panels (adjust convergence) of a Sharp XG-P10XU Projector

Projectors based on 3LCD technology work by splitting the white light from the lamp into 3 beams colored red, green, and blue, passing each beam through one of three LCD panels, combining the 3 beams back into one through a prism, and finally focusing the combined beam onto a wall or screen. In this process, the positions of the three individual LCD panels must be carefully controlled to ensure proper convergence. If a panel becomes misaligned, the corresponding color will be offset from the other colors in the image a condition known as misconvergence. Small misalignments by a pixel or…
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June 25th, 2014

Numbers one can call to test phone reception quality

I’ve recently cut one of my phone lines from AT&T and transferred it to Republic Wireless. The phone is configured to make calls and send messages over wifi and use the Sprint network (Verizon roaming) when no wifi is available. $10/month buys me unlimited everything on wifi and unlimited voice and text on cellular (no cellular data). So far, I’ve been pleased with the service (once I figured out how to white-list wifi networks). Enough of the shameless promoting. When I received my new phone and service, I naturally wanted to test the reception quality of both the voip calls…
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May 29th, 2014

Update apt public keys in Debian to fix package authentication errors

The apt program for Debian uses public and private keys to validate packages downloaded from the repositories. You can learn all about it at https://wiki.debian.org/SecureApt. Public keys are stored in /etc/apt/trusted.gpg. If keys are missing, outdated, corrupted, etc. apt will complain when trying to install packages with an error like “The following signatures couldn’t be verified because the public key is not available”. You can choose to ignore the error. If so, when it reoccurs in the future you will see warnings like “WARNING: The following packages cannot be authenticated!”. The solution to this problem is to update your public…
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May 28th, 2014

Accessing status and diagnostic information for a Motorola Surfboard cable modem

My ISP (to protect its identity, let’s call it Flomflast) drops my internet connection frequently. During the latest occurrence, I noticed from my router’s status page that the WAN address had been assigned to 192.168.100.11. I was surprised to see this since I believed there was no connection to the ISP via the cable line. How could the ISP DHCP server assigned an ip address to the router? And why the private network address? I guessed that if the DHCP server was assigning addresses in the 192.168.100.x range then itself or another server (the gateway?) might be located at 192.168.100.1….
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May 1st, 2014

auth.log errors: pam_winbind.so missing

I had an authorization log (/var/lib/auth.log) was filling up with errors related to a missing pam_winbind.so library: May  1 01:25:01 servername CRON[1906]: pam_unix(cron:session): session opened for user root by (uid=0) May  1 01:25:01 servername CRON[1906]: pam_unix(cron:session): session closed for user root May  1 01:25:16 servername auth: PAM unable to dlopen(/lib/security/pam_winbind.so): /lib/security/pam_winbind.so: cannot open shared object file: No such file or directory May  1 01:25:16 servername auth: PAM adding faulty module: /lib/security/pam_winbind.so …over and over. I tried upgrading winbind to the latest version in the Debian stable repositories. I installed libpam-winbind (2:3.6.6-6+deb7u3 for both). Neither of those actions fixed the problem. The library, pam_winbind.so,…
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April 3rd, 2014

How libxi broke my system

After some package updates I could no longer log into my Debian/XFCE system. The display manager (gdm3) would start to load but show only a black screen and rotating/spinning cursor. There was no login box – no way for me to get to a desktop. Digging through the logs I saw no errors in Xorg.0.log.  Dmesg and the kernel logs were no help either.  My first clue was found in the /var/log/gdm3/:0-greeter.log.* logs. Each of these logs had just one line: *** Error in `/usr/bin/gnome-session’: malloc(): memory corruption: 0x000000000207c620 *** A memtest run showed no errors. Reinstalling gnome-session didn’t fix…
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March 31st, 2014

Managing an iPod Shuffle (2nd gen.) in Linux

I have an old second generation iPod Shuffle (model A1204). When I dug it out of storage it wouldn’t play any songs. I plugged it in to my mobile desktop running Debian and verified the file system could still be read. I transferred all of the existing songs off of the shuffle using Thunar and its handy renaming feature. In order to manage the tracks (i.e. add and remove songs) I needed a piece of Linux software with that capability. Unfortunately, the popular options, Banshee, Rhythmbox, and Amarok would all require that I update a significant amount of my system…
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March 20th, 2014

How to change “about:home” to anything in Firefox (Icecat, Iceweasel)

Before reading, please note that I’ve written this post with respect to Icecat 17.0.1 which is a rebranded version of Firefox. I can’t guarantee that things will work the same with Firefox or Iceweasel (another rebrand) or other versions of any of these Mozilla browsers. The concept of a home page is not well defined in Firefox. In Edit->Preferences there is a Home Page setting. When Firefox starts, this is the url that will be displayed. But it’s not the url displayed when a new tab is created or when visiting about:home. Those are two other, independent settings. The first…
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