Re: [Qemu-discuss] QEMU ARM test image: modifying arm_root.img

[Jakob Bohm]

On 1/11/2014 2:18 PM, jmf list wrote:
> Hello,
>
> I'm trying to modify the initrd (arm_root.img) for the QEMU ARM test 
> image (http://wiki.qemu.org/Testing#QEMU_disk_images). I am able to 
> extract it using gunzip and cpio, but I can't recreate the archive so 
> that the VM will boot properly (I get a kernel panic). I believe my 
> problem is with how I am invoking cpio: if I simply gunzip/zip the 
> existing initrd cpio archive the VM boots properly, but if I extract 
> and re-create the cpio archive (without modification) the boot fails. 
> So, I was wondering: could you tell me what cpio options you used 
> to create the arm_root.img archive?
>
> Pardon for any obvious issues I might be overlooking. I've never 
> delved into initrd before; I am actually just trying to set up 
> automated testing for some ARM code that was contributed to one of my 
> open source projects. I am a bit far down the rabbit hole, I'm afraid. 
> I've googled and searched the mailing lists but wasn't able to find a 
> solution to my problem.
>
> Thanks for all the great work regardless,
> Jon
>
> PS
>
> Here is how I am extracting the archive, after gunzip:
> $ cpio -i -vd -H newc < ../arm_root
>
> Here is how I am creating it, before gzipping it:
> $ rm ../arm_root
> $ find . -depth -print | cpio -o --format=newc > ../arm_root
Hmm, have you tried without "-depth" ?, I am not sure the kernel can
successfully unpack rootfs files to a directory which has not yet
been created
> Here is a snippet from the console when the kernel panic occurs:
> ...
> 802.1Q VLAN Support v1.8 Ben Greear <address@hidden 
> <mailto:address@hidden>>
> All bugs added by David S. Miller <address@hidden 
> <mailto:address@hidden>>
> VFP support v0.3: implementor 41 architecture 1 part 10 variant 9 rev 0
> Root-NFS: No NFS server available, giving up.
> VFS: Unable to mount root fs via NFS, trying floppy.
> VFS: Cannot open root device "<NULL>" or unknown-block(2,0)
> Please append a correct "root=" boot option
> Kernel panic - not syncing: VFS: Unable to mount root fs on 
> unknown-block(2,0)


Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  http://www.wisemo.com
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