February 5, 2008

Write Permission Problems with Apache? Check for SELinux…

While trying to install MediaWiki on my CentOS 4.5 box, PHP could not write the Wiki configuration file.  So, I conducted the standard checklist: Figure out what user and group Apache was using (apache/apache), Ensure that the path to the configuration…
January 29, 2008

Choosing Between Being Hacked and Accidentally Breaking Services

As is good practice, on internal mission critical systems that are accessible from the Web, we run automatic security patching utilities (like yum and Microsoft Update).  For example, we are currently running (and enjoying) Zimbra 4.5.10 OSS as our mail…
February 28, 2007

Dovecot Invalid Messageset Error and Solution

Though working for a long time, while trying to read their mail, two of our Thunderbird IMAP users suddenly received the error: “The current command did not succeed.  The mail server responded: Invalid messageset: ‑2147483648:*.” A bit of research revealed that…
October 27, 2006

Resolving CVS Commit Conflicts with Word Documents

CVS is extremely popular for configuration management (with Subversion quickly gaining speed).  It uses “optimistic locking” in which multiple users can work on the same file at the same time, and any conflicts are resolved when the file is “checked-in”. …
October 25, 2006

TinyMCE, Spellchecker, and Firefox Crashes

TinyMCE is a powerful JavaScript-based WYSIWYG HTML editor that you can embed into TEXTAREA fields of your Web forms.  In addition, a PHP based spell checking system called Spellchecker allows TinyMCE to highlight unknown words (using aspell or Google’s spelling Web service).…
September 19, 2006

An Exercise Left to the Reader in “Godel’s Proof” by Nagel and Newman

In 1931, the mathematician Kurt Godel showed that any axiomatic system in natural number theory that is “complete” (can prove every postulate that is true) will not be “consistent” (it will prove a postulate that is false).  While having an impact…
August 31, 2006

Dreaming of an English-Based Object Oriented Language

MIT’s media lab has created “Metaphor”, a facinating tool that parses standard English into a programmatic pseudo-code.  Take a look at: http://www.trnmag.com/Stories/2005/032305/Tool_turns_English_to_code_032305.html.  Metaphor seems very cool, but to deal with the ambiguities of its English parser, it ends up with non-working pseudo-code.  They…
May 3, 2006

CPAN (Net::FTP) for Perl Hangs on Cygwin

CPAN is an essential tool for Perl developers.  With the “cpan” command, you can install whole Perl libraries effortlessly.  However, on many default installations of cygwin, cpan simply hangs: cpan> install LWP CPAN: Storable loaded ok Going to read /root/.cpan/MetadataDatabase…
April 12, 2006

Recovering RAID on Linux in Rescue Mode

The software RAID on Linux works very well.  Our backup machine (still using Red Hat 9) uses a RAID‑5 with 6 drives: 4 hot and 2 reserve.  When a main drive fails, a reserve is auto-magically brought in (thanks to the “md” daemon). But last Sunday…
December 15, 2005

Copying Text from Encrypted PDF Files

PDF encryption is sort of silly.  If you really wanted to grab the text, you can screen capture each page and then OCR it.  So clearly the true intention of the encryption is to deter the 99% of the users…