[Buildroot] Kernel panic - unable to mount root fs on unknown-block(0, 0) - i486

[Buildroot] Kernel panic - unable to mount root fs on unknown-block(0, 0) - i486

[Pongrácz István]

 Hi,

I have a problem with booting kernel built by buildroot on i486. The kernel (3.18.x) panicked: Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

I use the latest buildroot, the target is i486. I used a kernel config from a known working older kernel and double checked, all ext2/ext3 etc. built directly to the kernel, so, seems every necessary drivers built directly to the kernel (not as modules).

I tried to boot from usb. There is no initramfs (initrd).

If I get a different kernel from an other system, which is working, and I started the buildroot generated system with that kernel, it can boot as expected. Same kernel parameters.

Does it sound familiar to somebody?

My goal is to get a console based system optimized to i486, including kernel.

What am I missing?

Thanks, 

Istv?n
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[Buildroot] Kernel panic - unable to mount root fs on unknown-block(0, 0) - i486

[Yann E. MORIN]

Pongr?cz, All,

[Please, wrap lines at aronf ~72 chars, it's easier to read]

On 2015-04-24 22:34 +0200, Pongr?cz Istv?n spake thusly:
> I have a problem with booting kernel built by buildroot on i486. The
> kernel (3.18.x) panicked: Kernel panic - not syncing: VFS:
> Unable to mount root fs on unknown-block(0,0)
[--SNIP--]
> I tried to boot from usb.  There is no initramfs (initrd).

For the record so it gets archived on the list, after our discussion
on IRC:

  - add 'rootwait' to the kernel command line, as USB can be pretty slow
    to enumerate the devices on the bus

Kernel seems to wait forever, so:

  - check that all is built-in: USB driver, USB mass-storage, SCSI
    support, SCSI disk support (maybe a few things else...)

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
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[Buildroot] Kernel panic - unable to mount root fs on unknown-block(0, 0) - i486

[Pongrácz István]

 
 
----------------eredeti ?zenet-----------------
Felad?: "Yann E. MORIN" yann.morin.1998 at free.fr 
C?mzett: "Pongr?cz Istv?n" 
CC: "buildroot busybox.net" buildroot at busybox.net 
D?tum: Fri, 24 Apr 2015 23:49:51 +0200
-------------------------------------------------
 
 
> Pongr?cz, All,
> 
> [Please, wrap lines at aronf ~72 chars, it's easier to read]
> 
> On 2015-04-24 22:34 +0200, Pongr?cz Istv?n spake thusly:
>> I have a problem with booting kernel built by buildroot on i486. The
>> kernel (3.18.x) panicked: Kernel panic - not syncing: VFS:
>> Unable to mount root fs on unknown-block(0,0)
> [--SNIP--]
>> I tried to boot from usb. There is no initramfs (initrd).
> 
> For the record so it gets archived on the list, after our discussion
> on IRC:
> 
> - add 'rootwait' to the kernel command line, as USB can be pretty slow
> to enumerate the devices on the bus
> 
> Kernel seems to wait forever, so:
> 
> - check that all is built-in: USB driver, USB mass-storage, SCSI
> support, SCSI disk support (maybe a few things else...)
> 
> Regards,
> Yann E. MORIN.
> 
> -- 

Follow up.
I just created a new kernel from an "older" and proven working kernel.
3.16.7 - with initramfs. this kernel built outside of buildroot several months ago.
-> .config copied to the 3.18.6 for buildroot, make oldconfig
3.18.6 - new kernel based on 3.16.7, without initrd

kernel parameters are identical in both cases.

The system built, the result is the following:
- with kernel 3.18.6 - kernel panic (same as the original problem)
- with 3.16.7 - the system boots up as expected. lsmod shows nothing (no module loaded...)

So, I am working on fixing this issue.

It should be something trivial, what I simply missed.
I guess an initrd would be handy.

Bye,
Istv?n

[Buildroot] Kernel panic - unable to mount root fs on unknown-block(0, 0) - i486

[Steve Calfee]

On Fri, Apr 24, 2015 at 4:08 PM, Pongr?cz Istv?n
<pongracz.istvan@gmail.com> wrote:
>
>
> ----------------eredeti ?zenet-----------------
> Felad?: "Yann E. MORIN" yann.morin.1998 at free.fr
> C?mzett: "Pongr?cz Istv?n"
> CC: "buildroot busybox.net" buildroot at busybox.net
> D?tum: Fri, 24 Apr 2015 23:49:51 +0200
> -------------------------------------------------
>
>
>> Pongr?cz, All,
>>
>> [Please, wrap lines at aronf ~72 chars, it's easier to read]
>>
>> On 2015-04-24 22:34 +0200, Pongr?cz Istv?n spake thusly:
>>> I have a problem with booting kernel built by buildroot on i486. The
>>> kernel (3.18.x) panicked: Kernel panic - not syncing: VFS:
>>> Unable to mount root fs on unknown-block(0,0)
>> [--SNIP--]
>>> I tried to boot from usb. There is no initramfs (initrd).
>>
>> For the record so it gets archived on the list, after our discussion
>> on IRC:
>>
>> - add 'rootwait' to the kernel command line, as USB can be pretty slow
>> to enumerate the devices on the bus
>>
>> Kernel seems to wait forever, so:
>>
>> - check that all is built-in: USB driver, USB mass-storage, SCSI
>> support, SCSI disk support (maybe a few things else...)
>>
>> Regards,
>> Yann E. MORIN.
>>
>> --
>
> Follow up.
> I just created a new kernel from an "older" and proven working kernel.
> 3.16.7 - with initramfs. this kernel built outside of buildroot several months ago.
> -> .config copied to the 3.18.6 for buildroot, make oldconfig
> 3.18.6 - new kernel based on 3.16.7, without initrd
>
> kernel parameters are identical in both cases.
>
> The system built, the result is the following:
> - with kernel 3.18.6 - kernel panic (same as the original problem)
> - with 3.16.7 - the system boots up as expected. lsmod shows nothing (no module loaded...)
>
> So, I am working on fixing this issue.
>
> It should be something trivial, what I simply missed.
> I guess an initrd would be handy.
>
Interesting. Possibly related. I run tests on arm linux on a Marvel
kirkwood platform called dockstar.

I bought a new PC so I reinstalled buildroot. I built a with the
latest default kernel and linux hangs after uboot. I moved back to the
previous kernel version that worked 3.16.4 and it booted via nfs and
worked again.

So then I did a little binary searching and found kernels up to 3.16.7
boot properly, but 3.17 does not. So it looks like the uboot/kernel
environment broke starting at 3.17. I get no messages after uboot
starts the kernel. Does anyone know what to try next?

Regards, Steve

[Buildroot] Kernel panic - unable to mount root fs on unknown-block(0, 0) - i486

[Pongrácz István]

 
 
----------------eredeti ?zenet-----------------
Felad?: "Steve Calfee" stevecalfee at gmail.com 
C?mzett: "Pongr?cz Istv?n" 
CC: "Yann E. MORIN" yann.morin.1998 at free.fr , "buildroot busybox.net" buildroot at busybox.net 
D?tum: Sat, 25 Apr 2015 15:18:28 -0700
-------------------------------------------------
 
 
> 
> So then I did a little binary searching and found kernels up to 3.16.7
> boot properly, but 3.17 does not. So it looks like the uboot/kernel
> environment broke starting at 3.17. I get no messages after uboot
> starts the kernel. Does anyone know what to try next?
>


Hi Steve,

Thank you very much for your response. Now I compile kernel 3.16 to see, what happens. 
Everything else are unchanged.

The other test will be, I will compile 3.18 outside of buildroot, into standard deb package, including initrd, without changing the kernel config. 

Bye,
Istv?n