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

[Manos Pitsidianakis <manos.pitsidianakis@linaro.org>]

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>
>---