Re: [Qemu-devel] qemu-img qcow and raw format

[Ben Taylor]

---- Francois Visconte <address@hidden> wrote: 
> Hello,
> 
> I'm currently developing an OS deployment tool similar to G4U (ghost for 
> unix).
> This is a very basic tool
>   - boot an initrd
>   - configure network
>   - ssh deployment-server "cat image.dd"  > /dev/sda
>   - reboot
> 
> 
> I'm using qemu to test my initrd and deployment tool and i would like 
> replace my raw image format with qcow images (size/compression and crypto)
> 
>   - ssh deployment-server "cat image.qcow" | qemu-img - -O raw /dev/sda
> 
> The problem is qemu-img can't read from stdin, so i tried :
> 
>   - mkfifo deploy-in.fifo
>   - qemu-img convert deploy-in.fifo -O raw /dev/sda
>   - ssh deployment-server "cat image.qcow" > deploy-in.fifo
>     qemu-img: Could not open 'deploy-in.fifo'

I have not looked at the code in qemu-img (and the associated 
routines).  It appears that qemu-img is probably looking for
a file handle and not a named pipe. Either that, or you need
to shove the ssh command in the background before the 
qemu-img command so qemu-img has a chance to
start processing the data.  It's not clear whether or not
qemu-img is seeing an "empty file" because there's no
data on the pipe, or it can't read from the pipe.

Ben