[V3,4/9] qemu-img: add documentation for compress settings

Commit Message

Peter Lieven July 14, 2017, 9:56 a.m. UTC

Signed-off-by: Peter Lieven <[e-mail]>
---
 qemu-img.texi | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

Patch

diff --git a/qemu-img.texi b/qemu-img.texi
index f11f603..79b0182 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -669,6 +669,26 @@  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. Versions of QEMU before 2.10
+      will not be able to open images with this extension.
+
+@item compress.level
+Valid for compress.format=zlib defines the compression level to use for
+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 9 for the best compression.
+
 @end table
 
 @item Other