emerge virtualbox-modules virtualbox-ose

# emerge virtualbox-modules virtualbox-ose
Calculating dependencies... done!

>>> Verifying ebuild manifests

>>> Starting parallel fetch

>>> Emerging (1 of 4) app-emulation/virtualbox-modules-2.2.4
* vbox-kernel-module-src-2.2.4.tar.bz2 RMD160 SHA1 SHA256 size ;-) ... [ ok ]
* checking ebuild checksums ;-) ... [ ok ]
* checking auxfile checksums ;-) ... [ ok ]
* checking miscfile checksums ;-) ... [ ok ]
* Determining the location of the kernel source code
* Unable to find kernel sources at /usr/src/linux
* This package requires Linux sources.
* Please make sure that /usr/src/linux points at your running kernel,
* (or the kernel you wish to build against).
* Alternatively, set the KERNEL_DIR environment variable to the kernel sources location
*
* ERROR: app-emulation/virtualbox-modules-2.2.4 failed.
* Call stack:
* ebuild.sh, line 49: Called pkg_setup
* virtualbox-modules-2.2.4.ebuild, line 31: Called linux-mod_pkg_setup
* linux-mod.eclass, line 578: Called linux-info_pkg_setup
* linux-info.eclass, line 696: Called die
* The specific snippet of code:
* get_version || die "Unable to calculate Linux Kernel version"
* The die message:
* Unable to calculate Linux Kernel version
*
* If you need support, post the topmost build error, and the call stack if relevant.
* A complete build log is located at '/var/lib/entropy/logs/app-emulation:virtualbox-modules-2.2.4:20090617-004539.log'.
* The ebuild environment file is located at '/var/tmp/portage/app-emulation/virtualbox-modules-2.2.4/temp/die.env'.
*

>>> Failed to emerge app-emulation/virtualbox-modules-2.2.4, Log file:

>>> '/var/lib/entropy/logs/app-emulation:virtualbox-modules-2.2.4:20090617-004539.log'
#