You are correct Marvin. Upon locally checking the installed contents of the headers package (/var/lib/dpkg/info/linux-headers-2.6.28-14-generic.list), it does indeed come with the autoconf.h file. The site packages.ubuntu.com appears to not be keeping up with the latest packages. Therefore, it is reporting incomplete information. Additionally, something must have removed the file. What that is, I wish I knew! I will see if there is anything I can do to discover what might have tampered with that file. After reinstalling the headers- # apt-get install linux-headers-2.6.28-14-generic --reinstall The file autoconf.h is now again present. We have established that (at least on debian based systems), that /lib/modules/`uname -r`/build/include/linux/autoconf.h is nothing but a symbolic link to the real file located at /usr/src/linux-headers-`uname -r`/include/linux/autoconf.h Stephen Pinker