From a675ca4c620e66c1d45d55037f8fc21286af58cd Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 1 Sep 2023 12:24:30 +0200 Subject: qemu-img: Update documentation for compressed images Document the 'compression_type' option for qcow2, and mention that streamOptimized vmdk supports compression, too. Reported-by: Richard W.M. Jones Signed-off-by: Kevin Wolf Message-ID: <20230901102430.23856-1-kwolf@redhat.com> Reviewed-by: Richard W.M. Jones Signed-off-by: Kevin Wolf --- 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 15aeddc..ca5a277 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. -- cgit v1.1