root@mythtv:/home/mythtv# apt-get install linux-headers-`uname -r`
Reading package lists... Done
Building dependency tree... Done
Package linux-headers-2.6.18-chw-13 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package linux-headers-2.6.18-chw-13 has no installation candidate