Q: Keeping kernel and source synchronized

[D. R. Evans]

Some recent update seems to have put my kernel and the kernel source
headers out of sync.

uname -a gives:

Linux homebrew 2.6.15-27-amd64-generic #1 SMP PREEMPT Sat Sep 16
01:50:50 UTC 2006 x86_64 GNU/Linux

but ls -al /usr/src gives:

total 16
drwxrwsr-x  4 root src  4096 2006-08-31 20:52 .
drwxr-xr-x 12 root root 4096 2006-08-05 18:00 ..
drwxr-xr-x 19 root root 4096 2006-09-16 08:26 linux-headers-2.6.15-26
drwxr-xr-x  4 root root 4096 2006-09-16 08:26
linux-headers-2.6.15-26-amd64-generic

I would have expected these two to stay in sync if I stayed current
with all my updates, but that seems not to be the case.

How do I get them back in sync?