linux-kernel - Re: ramdisk

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Message-ID: <46DC9700.7070208@tmr.com>
Date:	Mon, 03 Sep 2007 19:21:36 -0400
From:	Bill Davidsen <davidsen@....com>
To:	Xu Yang <risingsunxy@...glemail.com>
CC:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: ramdisk

Xu Yang wrote:
> thanks for the reply.
>
> no , it is not decompressed. isn' t the kernel supposed to do that? As
> we have tried to load this filesystem on the pc, it turns out the the
> kernel can recognize it.
>
> concerning the root=/dev/ram0,
> as the default value is root=/dev/nfs, so I just modify the nfs to
> ram0. is this might be a problem?
>
>   
Hopefully someone who works with this regularly can provide some 
answers, the only time I used booting into a RAM-only system the tools 
which I had "just worked" and I followed the steps outlined without 
fully understanding the details. However, I just tried loop mounting a 
compressed filesystem and that didn't work, while decompressing into a 
ramdisk and mounting worked fine. That's why I asked if your tool was 
just copying to RAM without decompression, since I have no ides what 
tool you use.

As for the name, your original post used "dev" without a leading "/" and 
while I assumed it was a typo, I thought it was worth mentioning since 
you were looking for suggestions. I would expect /dev/ram0 to be correct.

I would try the decompressed image next, and I have no other ideas at 
the moment.
> regards,
>
>
> 2007/9/3, Bill Davidsen <davidsen@....com>:
>   
>> Xu Yang wrote:
>>     
>>> Hi everyone,
>>>
>>> I want to use ramdisk to boot my filesystem, as I can't use NFS and harddisk.
>>>
>>> I have load the ramdisk into the ram memory (start address :0x4000000)
>>>
>>> and in the boot options I specified : root =dev/ram0 initrd=0x4000000
>>>
>>> but the kernel said it can not find any file system on it.
>>>
>>>       
>> Looking at the information below, did the program which loaded the
>> filesystem into RAM decompress it? It noted that it was compressed so I
>> would assume so, but I am unfamiliar with ARM tools, so I ask the
>> question. Also, should the boot device be "/dev/ram0" rather than
>> "dev/ram0" or is that correct for your system?
>>
>>     
>>> Here is the information I can supply :
>>> U-Boot 1.2.0 (Aug 31 2007 - 20:54:55)
>>>
>>> ***  Auto-detects ethernet chip ***
>>>
>>>
>>>
>>> DRAM:   0 kB
>>> ## Unknown FLASH on Bank 1 - Size = 0x00000000 = 0 MB
>>> Flash:  0 kB
>>> *** Warning - bad CRC, using default environment
>>>
>>> In:    serial
>>> Out:   serial
>>> Err:   serial
>>>
>>> Hit any key to stop autoboot:  0
>>> ## Booting image at 00007fc0 ...
>>>    Image Name:   Linux-2.6.19-arm2
>>>    Image Type:   ARM Linux Kernel Image (uncompressed)
>>>    Data Size:    740372 Bytes = 723 kB
>>>    Load Address: 00008000
>>>    Entry Point:  00008000
>>> OK
>>>
>>>
>>> ## Loading Ramdisk Image at 04000000 ...
>>>    Image Name:   ramdisc
>>>    Image Type:   ARM Linux RAMDisk Image (gzip compressed)
>>>    Data Size:    12582962 Bytes = 12 MB
>>>    Load Address: 04000000
>>>    Entry Point:  04000000
>>>
>>> Starting kernel ...
>>>
>>>
>>> .........................................................................................
>>>
>>> RAMDISK driver initialized: 16 RAM disks of 10240K size 1024 blocksize
>>> <6>loop: loaded (max 8 devices)
>>> <6>mice: PS/2 mouse device common for all mice
>>> <6>VFP support v0.3: implementor 41 architecture 1 part 20 variant b rev 3
>>> No filesystem could mount root, tried:  ext2 cramfs vfat
>>> <0>Kernel panic - not syncing: VFS: Unable to mount root fs on
>>> unknown-block(1,0)
>>>
>>>
>>> Who can give me some hints ? or point me some direction to handle this.
>>>
>>> I appreciate this very much.
>>>
>>> regards,
>>>
>>> Yang
>>>       
>> --
>> Bill Davidsen <davidsen@....com>
>>   "We have more to fear from the bungling of the incompetent than from
>> the machinations of the wicked."  - from Slashdot
>>
>>     
>
>   


-- 
bill davidsen <davidsen@....com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

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