Signed-off-by: Peter Lieven <pl@kamp.de>
---
 qemu-img.texi | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/qemu-img.texi b/qemu-img.texi
index 5b925ec..430f0b9 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -621,6 +621,27 @@ file which is COW and has data blocks already, it couldn't be changed to NOCOW
 by setting @code{nocow=on}. One can issue @code{lsattr filename} to check if
 the NOCOW flag is set or not (Capital 'C' is NOCOW flag).
 
+@item compress.format
+Defines which compression algorithm is should be used for compressed clusters.
+The following options are available if support for the respective libraries
+has been enabled at compile time:
+
+   zlib            Uses standard zlib compression
+
+The compression algorithm can only be defined at image create time and cannot
+be changed later.
+
+Note: defining a compression format will result in the compression format
+      extension being written to the Qcow2 image. Older versions of QEMU will
+      not be able to open images with this extension.
+
+@item compress.level
+Defines which compression level is used for the selected compression format.
+The default of @code{compress.level=0} will use the default compression level
+for the format. Alternate values range from 1 for fastest compression to
+x for the best compression (x max vary between compression formats). This is
+always a trade in of compression speed against compressed size.
+
 @end table
 
 @item Other
-- 
1.9.1

Am 29.06.2017 um 12:57 hat Peter Lieven geschrieben:
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>  qemu-img.texi | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/qemu-img.texi b/qemu-img.texi
> index 5b925ec..430f0b9 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -621,6 +621,27 @@ file which is COW and has data blocks already, it couldn't be changed to NOCOW
>  by setting @code{nocow=on}. One can issue @code{lsattr filename} to check if
>  the NOCOW flag is set or not (Capital 'C' is NOCOW flag).
>  
> +@item compress.format
> +Defines which compression algorithm is should be used for compressed clusters.
> +The following options are available if support for the respective libraries
> +has been enabled at compile time:
> +
> +   zlib            Uses standard zlib compression
> +
> +The compression algorithm can only be defined at image create time and cannot
> +be changed later.
> +
> +Note: defining a compression format will result in the compression format
> +      extension being written to the Qcow2 image. Older versions of QEMU will
> +      not be able to open images with this extension.

Why not more specifically "QEMU versions before 2.10"?

> +@item compress.level
> +Defines which compression level is used for the selected compression format.
> +The default of @code{compress.level=0} will use the default compression level
> +for the format. Alternate values range from 1 for fastest compression to
> +x for the best compression (x max vary between compression formats). This is
> +always a trade in of compression speed against compressed size.

Start with something like "valid for compress.format=zlib" and then give
the exact range of valid values for zlib.

Kevin