localhost ~ # mkdir -p /var/db/pkg/sys-devel/linux-headers-2.6.19.2-r2
localhost ~ # echo sys-kernel> /var/db/pkg/sys-kernel/linux-headers-2.6.19.2-r2/CATEGORY
bash: /var/db/pkg/sys-kernel/linux-headers-2.6.19.2-r2/CATEGORY: Not a directory
localhost ~ # emerge -C =linux-headers-2.6.19.2-r2
!!! The short ebuild name "=linux-headers-2.6.19.2-r2" is ambiguous. Please specify
!!! one of the following fully-qualified ebuild names instead:
sys-devel/linux-headers
sys-kernel/linux-headers
localhost ~ # emerge -C =linux-headers-2.6.19.2-r2