[lfs-support] Can't Mount Root Filesystem

Роберт Киммель robert.l.kimmel at live.ru
Wed Mar 18 02:47:37 PDT 2015


On 18/3/15 17:14, Pierre Labastie wrote:
> Le 18/03/2015 09:11, Роберт Киммель a écrit :
>> Greetings All,
>>
>> I've been building LFS systems on and off for more than a decade, but
>> I've been struggling with this one for a while now.
>>
>> I have my 7.6 system installed, and when I boot, it seems like the
>> kernel loads, and everything goes as it should for a while.  But, when
>> it comes time to remount the root file system (which is the one where
>> the kernel was in the first place), it can't find it, kernel panic.
>>
>> I've checked all the relevant /etc and /boot files, and they seem OK, so
>> I suspect this is a matter of some kernel setting which is needed for
>> this particular hard disk, but which is not set properly.  All my
>> previous LFS systems were on what I'll call more "consumer" grade
>> hardware, but this one is a more up-market server platform.  So I think
>> probably I need to enable some option, some hardware driver, which I
>> never needed before.  However, I have tried a bunch of things, and
>> nothing works so far.
>>
>> My LFS 6.3 LiveCD boots on the same hardware no problem, and I can mount
>> the hard disk Linux partition, and do all the things one would normally
>> do to a hard disk, no problem.  So my thought was, maybe I can start
>> with the LFS 6.3 kernel settings, do a "make oldconfig" or something
>> similar on the kernel used in 7.6, and see if I can get the 7.6 system
>> to work that way.
>>
>> But I can't find the kernel settings for the LiveCD.  Are they on the CD
>> somewhere?
>>
>> Also, if anyone can think of a way to approach this problem which is
>> different than the one I'm pursuing, I'd appreciate any advice.
>>
>>
> I am not sure exactly when the panic occurs. Is it after init start
> (message 'INIT: version 2.88 booting') or before?
> If it is after, it means it is not a kernel issue, since it was able
> to load init. If it is before, I guess your approch is OK. You could
> try to install a modern distro, instead of the old LIve CD, and see
> what kernel modules are loaded once the system is started.
>
> Pierre
>

I can't capture the output, because the system is non-functional.  But,
what I can see on the screen is a bunch of messages, all beginning with
[   1.07XXXX], where XXXX is an increasing sequence.  The first message
(not literally the first one, but the first one at the top of the screen
after the whole process grinds to a halt) says "Hardware name: Dell
Inc.  Precision WorkStation T7500   /06FW8P BIOS A05 04/12/2010".

The next three consist entirely of hex numbers, I guess some kind of
memory dump.

After that, there is a "Call Trace:", which has a bunch of sub-messages
below it, with things like "dump_stack", "panic", "mount_block_root",
and a bunch of others.

Next to last message is "Kernel Offset: 0x0 from 0xc1000000 (relocation
range: 0xc0000000-0xf7ffdfff)"

Then the final message is "---[ end Kernel panic - not syncing: VFS:
Unable to mount roof fs on unknown-block(8,2)"

I can't vouch for perfect accuracy above, because I'm reading messages
from one computer's screen and typing them on another computer's
keyboard.  I don't see the "INIT" message which you reference, but the
screen scrolls so quickly I can't read the messages before these, and I
don't know how to capture them, if that's even possible.

I think this is the point where the kernel is trying to mount the
filesystem for the first time though - does that sound correct?

Merci beaucoup,

РК



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