Re: [PATCH v4] scripts/qcow2-to-stdout.py: Add script to write qcow2 images to stdout

[Kevin Wolf <kwolf@redhat.com>]

Am 30.07.2024 um 16:15 hat Alberto Garcia geschrieben:
> 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.
> 
> Implementing this directly in qemu-img is not really an option because
> it expects the output file to be seekable and it is also meant to be a
> generic tool that supports all combinations of file formats and image
> options. Instead, this tool can only produce qcow2 files with the
> basic options, without compression, encryption or other features.
> 
> 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-nbd
> or qemu-storage-daemon manually instead.
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> Signed-off-by: Madeeha Javed <javed@igalia.com>

Thanks, applied to the block branch.

Kevin