Compdigitec Labs


Make fails silently

Tuesday, February 28th, 2017

Run make -d &> log.txt and examine the log. Likely there is some prerequisite which is missing, in the form of “File `foo’ does not exist.”

LaTeX macros ending in numbers

Saturday, February 13th, 2016

Only letters are directly permitted in macro names, but by using csname to create definitions along with a variable command, we can simulate them. First, define the macros with numbers using \csname: Now, create a command which takes in one variable argument, and simply expands it to call the appropriate macro (“xR” + variable) defined […]

Reverse proxy with HTML rewriting using Apache

Sunday, May 25th, 2014

Importing upstream tarballs in Debian with gbp import-orig

Sunday, October 6th, 2013

To build it:

Apache Active Directory authentication

Sunday, September 15th, 2013

Add this to /etc/ldap/ldap.conf: Then add this to a block:

Reverse proxy HTTPS with Apache

Friday, August 23rd, 2013

The procedure is mostly similar to the procedure with regular HTTP, but there are a few gimmicks involved here: Generate a self-signed one or purchase a SSL certificate (*.crt) for the server in question. Make sure you run ‘sudo a2enmod ssl‘ to enable SSL. Make sure you have enable the proxy module with ‘sudo a2enmod […]

CUPS web interface not working

Saturday, August 17th, 2013

CUPS seems to be working fine - documents can be printed and everything seems to work fine, but the web interface at http://localhost:631/ doesn’t work, returning something like: “Firefox can’t establish a connection to the server at localhost:631.” Solution: Open /etc/cups/cupsd.conf as root and ensure that the line: Exists somewhere in the file. Then save […]

OpenGL acceleration in Debian/Ubuntu

Thursday, June 20th, 2013

Getting “Error:  couldn’t get an RGB, Double-buffered visual“? 1) Install video driver Example: 2) Install OpenGL and related libraries/tools: 3) Restart X server or restart computer: 4) Test acceleration: Sample working output:

Generating slope fields / direction fields with python and gnuplot

Sunday, April 21st, 2013 (1.9 KB) Now you can generate your own slope field / vector field / direction field of a differential equation using open source python and gnuplot! Set function to draw field of under dy_dx(). Set window parameters (x/y minimums and maximums, intervals, and length of field arrows). Run with to generate the slope field.

Compiling mingw-w64 with GCC 4.8

Thursday, February 7th, 2013

You need at least mingw-w64 rev 5579, build-essential, and a working compiler. Be sure to have installed flex and bison. Replace the demo prefix /usr/i686-w64-mingw32 with whatever you feel like, if you want to. Extract the gcc tarball, and pull in mpfr, mpc, and and gmp tarballs under the extracted gcc root. And just for […]

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