From: "John Beamish" 

It's a lyric from a 60's? 70's? pop tune.

Here's the note on BoingBoing:

Linux Thinkpads can be controlled by knocking on them.

There's a utility for Thinkpads running GNU/Linux that lets you execute
commands by physically knocking on the machine. This registers as activity
on the accelerometer built into the laptop (used to park the hard-drive
heads in the even of a fall) and is translated into commands within the OS.


This is the quote they pulled from the IBM site reporting it:

For the first time, you can hit your computer and get a meaningful
response! Using Linux and the Hard Drive Active Protection System (HDAPS)
kernel drivers, you can access the embedded accelerometers on Lenovo
(formerly IBM) ThinkPads, then process the accelerometer data to read
specific sequences of "knocking" events -- literally rapping on
the laptop case with your knuckles -- and run commands based on those
knocks. Double tap to lock the screen, and knock in your secret code to
unlock. Tap the display lid once to move your mp3 player to the next track.
The possibilities are endless.

And here's the link to the site

http://www-128.ibm.com/developerworks/linux/library/l-knockage.html?ca=dgr-lnxw
01Knock-Knock

--- BBBS/NT v4.01 Flag-5