[yocto] Yocto - Building initramfs to run a shell script for the support of IMA/EVM

[Rick Altherr]

Did you look at
http://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/recipes-core/images/core-image-minimal-initramfs.bb?
You do want to use the core-image class but some of the variables need to
be adjusted to build an initramfs.  OpenBMC does something similar to what
you are describing with their obmc-phosphor-initramfs (
https://github.com/openbmc/openbmc/blob/master/meta-phosphor/common/recipes-phosphor/images/obmc-phosphor-initramfs.bb)
that does a few things like applying staged rootfs updates before mounting
the rootfs.

On Fri, Jan 20, 2017 at 4:44 AM, Eswaran Vinothkumar (BEG-PT/PJ-IOT1) <
Vinothkumar.Eswaran at de.bosch.com> wrote:

> Hello Yocto community developers,
>
>
>
> I am currently working on the task of porting an existing build system to
> Yocto to create customized Linux distribution for an embedded product. I
> have successfully created a bare box image, the kernel and root file system
> image and the system startup is working fine.
>
>
>
> I am now investigating on creating the initramfs using Yocto and have gone
> through the Yocto documents for the same.
>
>
>
> Adding the options :
>
> INITRAMFS_FSTYPES = "cpio.gz"
>
> INITRAMFS_IMAGE = "custom-initramfs"  à my recipe which inherited
> core-image.bb recipe
>
>
>
> Results in the creation of ‘custom-image-20170120105621.rootfs.cpio.gz’
> file.
>
>
>
> We are using initramfs to run a script which before mounting the root file
> system checks for ima policy and also responsible for loading the evm-keys.
> In short, the initramfs contains a script which is executed before mounting
> the main root file system. So I think I need to follow a different
> procedure than the one I mentioned above for my use case. Also we are using
> systemd as the init system and for the initramfs I don’t need sysv or
> systemd as all I will do is running a script in initramfs.
>
>
>
> Is there a better way of creating this structure in Yocto, any information
> would be helpful.
>
>
>
>
>
> Mit freundlichen Grüßen / Best regards
>
>
>
> *Vinothkumar Eswaran BEG-PT/PJ-IOT1 *
> Tel. +49(7062)911-02 <+49%207062%2091102>
>
>
> --
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> yocto at yoctoproject.org
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>
>
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