[yocto] initramfs support in Yocto

[Joshua Immanuel]

Hello Darren,

On Fri, 2012-03-02 at 08:06 -0800, Darren Hart wrote:
> Can you be more specific about what you are looking for? When you
> build an image with the cpio.gz image type, you can boot that as an
> initramfs 

I find that the cpio.gz image is created by running the following
command inside ${IMAGE_ROOTFS} directory

	find . | cpio -o -H newc | gzip -c -9 > <name>.rootfs.cpio.gz

Which means that the initramfs contains the entire rootfs filesystem
including the user space applications and its related libraries. In my
case, the size of initramfs comes to 158 MB gziped to 66 MB. Most of the
files in that are not needed for initramfs.

Is there any other way of reducing the initramfs size?

Moreover, I find in the bootimg.bbclass file that it uses the INITRD and
ROOTFS variables to generate the final hddimage. And these variables
usage is seen in image-live.bbclass. So, I guess I have to point the
INITRD variable (in my custom-image.bb recipe and inherit bootimg) to
core-image-minimal-initramfs generated file in deploy images directory.

The problem with this method is 

     1. It uses syslinux bootloader by default. I have to override this
        class (bootimg.bbclass) if I want to use something else like
        grub.
     2. I have to point the INITRD variable directly to the initramfs
        file in the deploy directory. (like
        ${DEPLOY_DIR_IMAGE}/core-image-minimal-initramfs-${MACHINE}.cpio.gz). But the cpio.gz extension is based on machine configuration. It can be cpio, cpio.gz, cpio.xz or cpio.lzma

This is what I inferred from the existing code. Am I completely in the
wrong direction?

Regards
Joshua
-- 
Joshua Immanuel
HiPro IT Solutions Private Limited
http://hipro.co.in
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