[Buildroot] Booting from cramfs image

[Buildroot] Booting from cramfs image

[Hajime Yamasaki Vukelic]

Hi list,

I have an amlogic board (WetekPlay if anyone's familiar with it), and I
have a kernel image with initramfs, and a rootfs image in cramfs format.
The files involved are `boot.img` which is built using kernel uImage file,
DTB, and initramfs in cpio.gz format, and `rootfs.cramfs`. Both are written
to a FAT32 microSD card.

I'm trying to get the initramfs loop mount the cramfs image and switch_root
to it, but I keep getting kernel panic. The init script looks like this:

    https://gist.github.com/foxbunny/936438bf2ba67c2a5879

The error message:

    https://gist.github.com/foxbunny/fd9ceb120e8fe5a631aa

If someone could give me pointers on how to debug or fix this, I would
greatly appreciate it.


-- Hajime
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[Buildroot] Booting from cramfs image

[Thomas Petazzoni]

Hajime,

On Thu, 11 Feb 2016 21:36:38 +0100, Hajime Yamasaki Vukelic wrote:

> I have an amlogic board (WetekPlay if anyone's familiar with it), and I
> have a kernel image with initramfs, and a rootfs image in cramfs format.
> The files involved are `boot.img` which is built using kernel uImage file,
> DTB, and initramfs in cpio.gz format, and `rootfs.cramfs`. Both are written
> to a FAT32 microSD card.
> 
> I'm trying to get the initramfs loop mount the cramfs image and switch_root
> to it, but I keep getting kernel panic. The init script looks like this:
> 
>     https://gist.github.com/foxbunny/936438bf2ba67c2a5879
> 
> The error message:
> 
>     https://gist.github.com/foxbunny/fd9ceb120e8fe5a631aa
> 
> If someone could give me pointers on how to debug or fix this, I would
> greatly appreciate it.

Well, it essentially means that your init program on your real root
filesystem (in the cramfs image) does not work. Built for the wrong
architecture variant, missing libraries, etc. Could be lots of things.

Also, why use a cramfs filesystem rather than the modern modern and
efficient squashfs?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[Buildroot] Booting from cramfs image

[Hajime Yamasaki Vukelic]

Thomas,

On Fri, Feb 12, 2016 at 2:50 PM, Thomas Petazzoni
<thomas.petazzoni@free-electrons.com> wrote:
[SNIP]
> > If someone could give me pointers on how to debug or fix this, I would
> > greatly appreciate it.
>
> Well, it essentially means that your init program on your real root
> filesystem (in the cramfs image) does not work. Built for the wrong
> architecture variant, missing libraries, etc. Could be lots of things.

Ah, thanks, it hasn't occurred to me that would be the case. Is there
some way I can get useful output and maybe store it on the card for
debugging purposes?

> Also, why use a cramfs filesystem rather than the modern modern and
> efficient squashfs?

This is the first time I'm doing this type of setup, so simply lack of
experience, I guess. :)

-- Hajime

[Buildroot] Booting from cramfs image

[Hajime Yamasaki Vukelic]

Thomans,

I thank you again for your hints. Simply switching to squashfs seems
to have fixed the issue, so I assume it was some issue with mounting
the cramfs image.

-- Hajime

On Sat, Feb 13, 2016 at 11:22 AM, Hajime Yamasaki Vukelic
<hayavuk@gmail.com> wrote:
> Thomas,
>
> On Fri, Feb 12, 2016 at 2:50 PM, Thomas Petazzoni
> <thomas.petazzoni@free-electrons.com> wrote:
> [SNIP]
>> > If someone could give me pointers on how to debug or fix this, I would
>> > greatly appreciate it.
>>
>> Well, it essentially means that your init program on your real root
>> filesystem (in the cramfs image) does not work. Built for the wrong
>> architecture variant, missing libraries, etc. Could be lots of things.
>
> Ah, thanks, it hasn't occurred to me that would be the case. Is there
> some way I can get useful output and maybe store it on the card for
> debugging purposes?
>
>> Also, why use a cramfs filesystem rather than the modern modern and
>> efficient squashfs?
>
> This is the first time I'm doing this type of setup, so simply lack of
> experience, I guess. :)
>
> -- Hajime