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Re: [PATCH] qemu-img: Update documentation for compressed images
From: |
Richard W.M. Jones |
Subject: |
Re: [PATCH] qemu-img: Update documentation for compressed images |
Date: |
Fri, 1 Sep 2023 11:28:25 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, Sep 01, 2023 at 12:24:30PM +0200, Kevin Wolf wrote:
> Document the 'compression_type' option for qcow2, and mention that
> streamOptimized vmdk supports compression, too.
>
> Reported-by: Richard W.M. Jones <rjones@redhat.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Looks good, so:
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
> ---
> docs/tools/qemu-img.rst | 19 +++++++++++++++++--
> 1 file changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/docs/tools/qemu-img.rst b/docs/tools/qemu-img.rst
> index 15aeddc6d8..ca5a2773cf 100644
> --- a/docs/tools/qemu-img.rst
> +++ b/docs/tools/qemu-img.rst
> @@ -106,7 +106,11 @@ by the used format or see the format descriptions below
> for details.
>
> .. option:: -c
>
> - Indicates that target image must be compressed (qcow format only).
> + Indicates that target image must be compressed (qcow/qcow2 and vmdk with
> + streamOptimized subformat only).
> +
> + For qcow2, the compression algorithm can be specified with the ``-o
> + compression_type=...`` option (see below).
>
> .. option:: -h
>
> @@ -776,7 +780,7 @@ Supported image file formats:
>
> QEMU image format, the most versatile format. Use it to have smaller
> images (useful if your filesystem does not supports holes, for example
> - on Windows), optional AES encryption, zlib based compression and
> + on Windows), optional AES encryption, zlib or zstd based compression and
> support of multiple VM snapshots.
>
> Supported options:
> @@ -794,6 +798,17 @@ Supported image file formats:
> ``backing_fmt``
> Image format of the base image
>
> + ``compression_type``
> + This option configures which compression algorithm will be used for
> + compressed clusters on the image. Note that setting this option doesn't
> yet
> + cause the image to actually receive compressed writes. It is most
> commonly
> + used with the ``-c`` option of ``qemu-img convert``, but can also be used
> + with the ``compress`` filter driver or backup block jobs with compression
> + enabled.
> +
> + Valid values are ``zlib`` and ``zstd``. For images that use
> + ``compat=0.10``, only ``zlib`` compression is available.
> +
> ``encryption``
> If this option is set to ``on``, the image is encrypted with
> 128-bit AES-CBC.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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