[OE-core] zimage Initramfs booting stuck at Start Kernel

[Ferry Toth]

Op 27-10-2019 om 22:52 schreef JH:
> Hi Ferry,
> 
> On 10/27/19, Ferry Toth <fntoth at gmail.com> wrote:
>> Op 27-10-2019 om 02:27 schreef JH:
>>> Hi Ferry,
>>>
>>> On 10/27/19, Ferry Toth <fntoth at gmail.com> wrote:
>>>>
>>>> As an example you might want to look at my repo, I have 2 images minimal
>>>> and initramfs:
>>>> https://github.com/edison-fw/meta-intel-edison/tree/master/meta-intel-edison-distro/recipes-core/images
>>>>
>>>> I don't exactly know how you are doing it. But I'll try to explain what
>>>> I do:
>>>> I have
>>>> 1) a normal rootfs (say edison-image-minimal) and
>>>> 2) a initramfs rootfs containing kernel modules needed for booting and a
>>>> init script.
>>>>
>>>> Initramfs is build using core-image-minimal-initramfs.bbappend. Some
>>>> additional unneeded packages are pulled, and as size is restricted (10MB
>>>> or so?) we remove them here.
>>>
>>> Thanks for the tips, that confirms my long suspensions that the size
>>> of the image could be the cause of the problem, my working zImage size
>>> is 8MB, my failing zImager-initramfs size is 35MB. How did you remove
>>> the 10 MB size restriction? I checked your
>>
>> I don't. I reduce the contents as much as possible.
> 
> That is not practical, we cannot limit the kernel + rootfs to 10 MB size.
> 
>>> core-image-minimal-initramfs.bbappend, there is no sign to remove 10
>>> MB size restriction. You have a resize-rootfs.service, but I am not
>>> sure that is the one for fixing the 10 MB size restriction. The
>>
>> No, it isn't.
>>
>>> edison-image-minimal.bb has the IMAGE_ROOTFS_SIZE = "1048576", sorry
>>> for my dumb, is that size for 1048576 KB (1GB) or 1048576 B (1MB)?
>>
>> The rootfs is on disk (/) and is 1GB. It has nothing to do with initramfs.
> 
> OK.
> 
>>>> The init script is here:
>>>> https://github.com/edison-fw/meta-intel-edison/blob/master/meta-intel-edison-distro/recipes-core/initrdscripts/initramfs-framework/init
>>>>
>>>> The init script loads modules, waits for the disk with the rootfs to
>>>> appear and mount it. Then switchroot to it.
>>>> If it doesn't appear it drops to a shell so you can investigate what's
>>>> wrong.
>>>
>>> I am confident that the 10 MB size restriction is the problem, I am
>>> not clear where that 10 MB size restriction is defined and how to fix
>>> the size restriction, appreciate your helps.
>>
>> I am not sure where it comes from, I think internal in the kernel there
>> is a limit, after uncompress. Initramfs is in ram, I think we just need
>> to accept there is a size restriction.
> 
> No, there is no limitation in kernel, BTW, the zImage-initramfs is not
> just kernel space, the zImage-initramfs = kernel + rootfs which cannot
> be limited to 10 MB. I have a zImage-initramfs created by openwrt, the
> size is 28 MB. The problem is created by oe-core, most likely in
> kernel.bbclass, could anyone in oe-core development provide insights
> where is the 10 MB limitation from and how to fix it?

I see that Ubuntu keeps the initramfs in a separate cpio, while we are 
trying to build the cpio into the kernel (afaiu the cpio is unpacked 
into a kernel directory, and then built-in by the kernels build system).

And that cpio is ~64MB, so it must be possible.

In my case kernel, cpio and zImage-initramfs are all built. And although 
U-Boot allows to load kernel and cpio separately I didn't try (or don't 
remember the result). So, maybe that's the trick.

>>>> To build everything edison-image-minimal triggers build of u-boot,
>>>> kernel, rootfs, initramfs and kernel-with-built-in-initramfs.
>>>
>>>> Search for 'init' and 'live' and find the needed lines in
>>>> https://github.com/edison-fw/meta-intel-edison/blob/master/meta-intel-edison-distro/recipes-core/images/edison-image-minimal.bb
>>>
>>> I looked at the init script, but not clear if it is critical for
>>> fixing that issue or not. My init is the symblic link to
>>> /lib/systemd/systemd in imx6.
>>
>> Given the size restriction I think we have no choice to use initramfs to
>> load minimum required modules and then mount and switchroot to a file
>> system on disk. So, yes, you need to modify init for that. After
>> switchroot there will be a new init, the symbolic link you mention.
> 
> That is not good, we need to fix it. I am still new to oe-core,
> bitbake and Yocto, but I am happy to give a try if someone could point
> me where could be the source for the 10 MB limitation of
> zImage-initramfs.
> 
> Thank you very much.
> 
> Kind regards,
> 
> - jh
>