[yocto] How to build initramfs with modules but without bzImage

[Ferry Toth]

Op Mon, 22 May 2017 00:05:41 +0200, schreef Ferry Toth:

> I am building 2 images. One has my rootfs, the other builds a kernel
> with builtin initramfs.
> 
> To build the initramfs I did the following:
> In the .../conf directory, I create a file named initramfs.conf and add
> the following:
>  
> INITRAMFS_IMAGE = "core-image-minimal-initramfs"
> INITRAMFS_IMAGE_BUNDLE = "1"
>  
> IMAGE_FSTYPES = "cpio.gz"
>  
> Then to build the initramfs based on the core-image-base recipe, I
> execute the following bitbake command:
>  
>      bitbake -R conf/initramfs.conf core-image-minimal-initramfs
>  
> When it completes, there is a kernel + initramfs file in the .../tmp/
> deploy/images/..../  directory.
>  
> This image boots to the init script, but then hangs as the mmc drivers
> have not been included.
> 
> Now I create a core-image-minimal-initramfs.bbappend file and
> PACKAGE_INSTALL the modules I need (also tried kernel-modules).
> 
> Unfortunately this also installs the kernel bzImage in the /boot
> directory, that appears to be a dependancy. This adds another 6MB to my
> initramfs, which is now to load.
> 
> I expect it should be possible to add the modules without adding the
> kernel, but haven't been able to find a way to do that. Or it should be
> possible to remove the contents of /boot after do_rootfs.
> 
> But I have no clue how to do that.
> 
> Or am I just generating the initramfs in the wrong way?

Thanks people especially paulg and khem on irc,

I added to my core-image-minimal-initramfs.bbappend:

ROOTFS_POSTPROCESS_COMMAND += "clobber_unused"

clobber_unused () {
        rm ${IMAGE_ROOTFS}/boot/*
}

This shrink my initramfs just enough to boot. Of course I can remove more 
files if needed, by adding dir's to the clobber function.