I had a few users who have been using my bcSpamBlock WordPress plugin for blocking spam tell me that it also completely blocks trackbacks. Thanks to their input and specifically wlx who sent me a patch to have it skip validation on trackbacks and pingbacks.

I modified the WordPress component of the code so that it doesn’t check for the cryptographic signature for trackbacks, but instead makes sure that the remote host is the webserver for the site that it says it is. If that check passes, it also retrieves the page and verifies that it contains a link to your own blog.

I’ve updated the plugin and it is available for download on the bcSpamBlock wordpress page

I now have a bunch of email accounts each with their own IMAP folders.   It has been terribly annoying that they always show up in the order in which the accounts were added and there is no way to sort them.   I finally came across a Thunderbird plugin called ‘Folderpane Tools‘ which allows you to change the order of the accounts.

It still isn’t ideal.  Any changes have to be done through the little plugins window and require Thunderbird to be restarted.  Oh well, I guess its better than nothing.

I’ve had a couple customers in the past month or so run into a problem where they were trying to run a simple Perl script, but kept getting HTTP 500 errors (Internal Server Error) despite double checking through their code, and simplifying it down to almost nothing. One had spent half a day troubleshooting a seemingly simple error. Apache would log something like this:

[Sat Nov 03 22:46:57 2007] [error] [client 11.22.33.44] (2)No such file or directory: exec of '/var/www/cgi-bin/hello.pl' failed
[Sat Nov 03 22:46:57 2007] [error] [client 11.22.33.44] Premature end of script headers: hello.pl

By time they contacted me, they were so frustrated, that it is hard to tell them how easy the fix is. In both cases, the users had created the files on a Windows machine and then uploaded them to a Linux server. Many windows applications happen to save text files in a slightly different format than Linux does. Specifically, windows uses the two characters CR and LF (Carriage Return, and Line Feed), where Linux simply uses just a LF.

Carriage Return is the ASCII character 13, and is also recognized as ‘\r’, or ‘^M’. The Line Feed character is ASCII code 10, and represented as ‘\n’, or ‘^J’.

An attempt to run this same ‘hello.pl’ script via a command line results in:

[root@host cgi-bin]# ./hello.pl
: bad interpreter: No such file or directory

To fix, simply convert the file to a Unix text file format. Your text editor may have an option to save the file in a Unix format. If you are stuck with the editor you have, you can use the ‘dos2unix‘ command which is available on pretty much any Linux box.

[root@host cgi-bin]# dos2unix hello.pl
dos2unix: converting file hello.pl to UNIX format ...

And now your script will magically work (You did remember to add the content-type header, right):

[root@flickerworks cgi-bin]# ./hello.pl
Content-type: text/html

Hello World

When your server is located in a data center far away, it makes it difficult to walk over to the box and read the service tag off of it. Fortunately, the Service Tag is stored somewhere in the system BIOS, and is accessible with the ‘dmidecode’ utility.

[root@host ~]# dmidecode|grep "Serial Number"
                Serial Number: 80NZV71

You’ll probably see several other serial numbers in there as well for things like your hard drives or other devices. The Dell shouldn’t be too difficult to pick out. I think they are always 7 digits and have letters in middle. There is lots of other interesting things in the ‘dmidecode’ output too, like the speed and type of each RAM module installed, and a description of all of the onboard devices (ie: video and network cards)

With Windows

Thanks to @kleinbaas who commented below how to do the same thing on a Windows machine:

  C:\Documents and Settings\brandon>wmic bios get serialnumber
  SerialNumber
  GX245D1