Bug 7096

documentation only, so putting this in M4.

Hi, 

Will work on this when I get raw information.

Scott

BTW - Some updating has been done to the INITRAMFS_IMAGE (http://www.yoctoproject.org/docs/2.2/ref-manual/ref-manual.html#var-INITRAMFS_IMAGE) and the INITRAMFS_FSTYPES (http://www.yoctoproject.org/docs/2.2/ref-manual/ref-manual.html#var-INITRAMFS_FSTYPES) variables.  You should consider these in the solution as well. 

Thanks, 
Scott

Oh.. also, the description for INITRAMFS_IMAGE_BUNDLE has been enhanced as well - http://www.yoctoproject.org/docs/2.2/ref-manual/ref-manual.html#var-INITRAMFS_IMAGE_BUNDLE.

Scott

Changing to NEEDINFO as I need some raw steps for procedures.

Scott

I can add my 2 cents adding some little documentation about the old-way of embedding an initramfs in the kernel. Links to kernels 3.8 are now outdated.

https://github.com/kexecboot/kexecboot/wiki/oe-yocto


It appears there is only an hint in kernel.bbclass about this:

    # NOTE: setting INITRAMFS_TASK is for backward compatibility
    #       The preferred method is to set INITRAMFS_IMAGE, because
    #       this INITRAMFS_TASK has circular dependency problems
    #       if the initramfs requires kernel modules

If you think, you could expand a bit in the documentation.

Thanks for the extra bit Andrea... I still need information to move forward on this issue. 

Scott

I have been playing with initramfs stuff for other work recently, and I have more to add that might be of use...

To build an initramfs, and bundle it into the kernel, use the following variables:

INITRAMFS_IMAGE_BUNDLE = "1"
INITRAMFS_IMAGE = "<name of image recipe>"

With the INITRAMFS_IMAGE_BUNDLE flag set, the initramfs created by the recipe defined by INITRAMFS_IMAGE is unpacked into the ${B}/usr/ directory. That is then passed to the kernel's make via the CONFIG_INTRAMFS_SOURCE option, allowing it to be built in to the kernel in the normal way.

The recipe that INITRAMFS_IMAGE points to must produce a .cpio.gz, .cpio.tar, .cpio.lz4, .cpio.lzma, or .cpio.xz file (I also saw a patch adding support for plain uncompressed .cpio files recently, but not sure if that's in core yet). This can be done by setting the IMAGE_FSTYPES variable to one or more of the above.

Adding things to the initramfs image (in its recipe) should be done via PACKAGE_INSTALL = rather than IMAGE_INSTALL. PACKAGE_INSTALL gives more direct control of what is added to the image, as image.bbclass and/or core-image.bbclass set defaults that you do not necessarily want.

I think I have a decent general understanding of it now, so if you have any specific questions please do ask.

Hi, 

I looked at the example in the link in Comment 6.  It uses INITRAMFS_TASK, which is noted as having some circular issues.  So, I am not sure what to incorporate in the new section from that example.  I did put that "NOTE" you mentioned in the comment as a note in the new section on how to build an initramfs. 

Changes have been made:

 * The main new "how-to" section to create initramfs images - http://www.yoctoproject.org/docs/2.3/dev-manual/dev-manual.html#building-an-initramfs-image

 * Change to the kernel.bbclass description to include a cross-reference to the new "how-to" section in the dev-manual - http://www.yoctoproject.org/docs/2.3/ref-manual/ref-manual.html#ref-classes-kernel

Pretty much all the variables cross-referenced in the new "how-to" section now link back to the new section for explanation on how to build an initramfs.

Let me know if there are any changes or corrections needed.

thanks, 
Scott

I think that note is enough. Thanks.

I'd add two observations:

!) "To build an initramfs image and bundle it into the kernel, set the following variables: "
It is not clear that you must set INITRAMFS_IMAGE_BUNDLE = "1" in local.conf while INITRAMFS_IMAGE = "image_recipe_name" cab ne set in machine.conf or in the image.


2) "you produce one of these .cpio.* files by setting the IMAGE_FSTYPES variable"
I think that the right var to use is INITRAMFS_FSTYPES
This one can be set in machine.conf or even in the image.

Cheers

Andrea

Andrea, 

Thanks for the feedback.  See http://www.yoctoproject.org/docs/2.3/dev-manual/dev-manual.html#building-an-initramfs-image for the changes and let me know if there is anything else I need to fix. 

Scott

Looks good to me as well.

Cal, 

I set the doc flag to "done" since you set the issue to RESOLVED.  Also, updated the Whiteboard.

Thanks,
Scott