Re: [PATCH] scripts/qcow2-to-stdout.py: Add script to write qcow2 images to stdout

[Manos Pitsidianakis]

Hello Alberto,

On Mon, 10 Jun 2024 17:47, Alberto Garcia <berto@igalia.com> wrote:
> This tool converts a disk image to qcow2, writing the result directly
> to stdout. This can be used for example to send the generated file
> over the network.
>
> This is equivalent to using qemu-img to convert a file to qcow2 and
> then writing the result to stdout, with the difference that this tool
> does not need to create this temporary qcow2 file and therefore does
> not need any additional disk space.


Can you expand on this a little bit? Would modifying qemu-img to write 
to stdout if given, say, - instead of a file output path be enough to 
make this script unnecessary?


> The input file is read twice. The first pass is used to determine
> which clusters contain non-zero data and that information is used to
> create the qcow2 header, refcount table and blocks, and L1 and L2
> tables. After all that metadata is created then the second pass is
> used to write the guest data.
>
> By default qcow2-to-stdout.py expects the input to be a raw file, but
> if qemu-storage-daemon is available then it can also be used to read
> images in other formats. Alternatively the user can also run qemu-ndb
> or qemu-storage-daemon manually instead.
>
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> Signed-off-by: Madeeha Javed <javed@igalia.com>
> ---