Re: [Qemu-devel] format=raw,readonly errors

[Eric Blake]

On 05/08/2017 11:39 AM, Eric Blake wrote:
> On 05/08/2017 11:33 AM, Carl Karsten wrote:
>> according to the warning: "Specify the 'raw' format explicitly to remove
>> the restrictions."
>>
>> I want the restriction.
>>
>> format=raw, (write operations on block 0)=restricted
> 
> Then omit format=raw.  (It's an unusual request, though).  Or, as others
> mentioned in this thread, you can use -snapshot or any other form of
> overlay image to keep the original image read-only while still providing
> a read-write image that the guest requires for faithful hardware
> emulation; and you can always check your overlay after the fact to learn
> whether sector 0 was changed.

The only other solution I can think of is using the blkdebug wrapper
with a config-file that causes EIO errors on any time to write anywhere
in the range [0,511]; however, setting up blkdebug is not very-well
documented (best may be to inspect existing files in
tests/qemu-iotests/??? for usage of blkdebug).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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