Geotagged at home (51.427051,-0.333344)

X-Clacks-Overhead and GNU Terry Pratchett

So farewell Sir Terry Pratchett. Since I first read The Colour Of Magic in 1983 you made me smile, you made me laugh out loud and above all, you always made me think.

In 2004's Going Postal, Terry wrote about the clacks, a series of semaphore towers that were the Discworld equivalent of the old telegraph system. There was a tradition that when a clacks worker dies in the line of duty, their name would be sent home by being transmitted up and down the line in the signalling layer of the clacks message protocol.

His name, however, continues to be sent in the so-called Overhead of the clacks. The full message is "GNU John Dearheart", where the G means, that the message should be passed on, the N means "Not Logged" and the U that it should be turned around at the end of the line. So as the name "John Dearheart" keeps going up and down the line, this tradition applies a kind of immortality as "a man is not dead while his name is still spoken".

Today's analog of the clacks is the interwebs and in the clack towers you can see a hazy version of our web servers. It seems aptly fitting that there's an unofficial way of keeping Terry Pratchett's name alive by adding the X-Clacks-Overhead HTTP header to any content that a web server sends out into the interwebs at large. You'll never see these headers in a web browser, they're hidden from view, but they're there nonetheless. The fact that the routing instructions of G, N and U also mirrors the Free Software Foundation's GNU project may or may not be entirely intentional.


If you're so technically minded, you'll find that this site as well as my maps site are doing their little bit to make sure that Terry's name is still spoken, going up and down the line.

The usual map related musings will return in the next post.

1910 Telegraph Pole by Noel Hankamer on Flickr under CC-BY-NC

Gary Gale

I'm Gary ... a Husband, Father, CTO at Kamma, geotechnologist, map geek, coffee addict, Sci-fi fan, UNIX and Mac user