[yocto] initramfs image

[Manuel Bessler]

Hi,

I'm trying to figure out how to build an image of type initramfs, ie.
kernel with built-in rootfs.
I've got a rootfs.cpio.gz in build/tmp/deploy/images. But how do I
tell the kernel to actually use it
and "swallow in" the rootfs.

I've found a few variable that have to do with initramfs', but there
are no simple examples,
and for some variables I've not found any examples nor documentation at all.

in  .../images/myimage-initramfs.bb I have:
require myimage.bb
INITRAMFS_FSTYPES = "cpio.gz"
IMAGE_FSTYPES = "${INITRAMFS_FSTYPES}"

In the same file I tried to set INITRAMFS_IMAGE to:
INITRAMFS_IMAGE = "myimage "


Do I need to set CONFIG_INITRAMFS_SOURCE in my kernel config manually,
and if yes, to what?
My kernel recipe is (for now) a simple kernel build, ie "inherit
kernel"-based only.

Am I using INITRAMFS_IMAGE the right way? What about INITRAMFS_TASK ?
I could not find any information on this variable....

I'm using yocto 1.2.


Does anyone have a simple example on how to build a kernel with
initramfs built in?

I'd appreciate any help.
Thanks,
Manuel