docker: Add test_fail and prep_fail

[qemu.git] / qemu-img.texi

diff --git a/qemu-img.texi b/qemu-img.texi
index f11f6036ad01a5f2cded46be5daaf260fbcee79f..72dabd6b3e632a3a74c8f8f8ce185b80239df34d 100644 (file)
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -233,7 +233,7 @@ If @code{-r} is specified, exit codes representing the image state refer to the
 state after (the attempt at) repairing it. That is, a successful @code{-r all}
 will yield the exit code 0, independently of the image state before.
 
-@item create [-f @var{fmt}] [-b @var{backing_file}] [-F @var{backing_fmt}] [-o @var{options}] @var{filename} [@var{size}]
+@item create [-f @var{fmt}] [-b @var{backing_file}] [-F @var{backing_fmt}] [-u] [-o @var{options}] @var{filename} [@var{size}]
 
 Create the new disk image @var{filename} of size @var{size} and format
 @var{fmt}. Depending on the file format, you can add one or more @var{options}
@@ -244,6 +244,13 @@ only the differences from @var{backing_file}. No size needs to be specified in
 this case. @var{backing_file} will never be modified unless you use the
 @code{commit} monitor command (or qemu-img commit).
 
+Note that a given backing file will be opened to check that it is valid. Use
+the @code{-u} option to enable unsafe backing file mode, which means that the
+image will be created even if the associated backing file cannot be opened. A
+matching backing file must be created or additional options be used to make the
+backing file specification valid when you want to use an image created this
+way.
+
 The size can also be specified using the @var{size} option with @code{-o},
 it doesn't need to be specified separately in this case.