iotests: skip 048 with qcow which doesn't support resize

[qemu.git] / qemu-img.texi

diff --git a/qemu-img.texi b/qemu-img.texi
index c81db3e81cd0f9a4ec356790682f3bda7694b37e..f335139217b0d112605e640509f8b9084c6ef7b1 100644 (file)
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -45,9 +45,17 @@ keys.
 
 @item --image-opts
 
 
 @item --image-opts
 

-Indicates that the @var{filename} parameter is to be interpreted as a
+Indicates that the source @var{filename} parameter is to be interpreted as a

 full option string, not a plain filename. This parameter is mutually
 full option string, not a plain filename. This parameter is mutually

-exclusive with the @var{-f} and @var{-F} parameters.
+exclusive with the @var{-f} parameter.
+
+@item --target-image-opts
+
+Indicates that the @var{output_filename} parameter(s) are to be interpreted as
+a full option string, not a plain filename. This parameter is mutually
+exclusive with the @var{-O} parameters. It is currently required to also use
+the @var{-n} parameter to skip image creation. This restriction may be relaxed
+in a future release.

 
 @item fmt
 is the disk image format. It is guessed automatically in most cases. See below
 
 @item fmt
 is the disk image format. It is guessed automatically in most cases. See below


@@ -84,7 +92,8 @@ with or without a command shows help and lists the supported formats
 @item -p
 display progress bar (compare, convert and rebase commands only).
 If the @var{-p} option is not used for a command that supports it, the
 @item -p
 display progress bar (compare, convert and rebase commands only).
 If the @var{-p} option is not used for a command that supports it, the

-progress is reported when the process receives a @code{SIGUSR1} signal.
+progress is reported when the process receives a @code{SIGUSR1} or
+@code{SIGINFO} signal.

 @item -q
 Quiet mode - do not print any output (except errors). There's no progress bar
 in case both @var{-q} and @var{-p} options are used.
 @item -q
 Quiet mode - do not print any output (except errors). There's no progress bar
 in case both @var{-q} and @var{-p} options are used.


@@ -224,7 +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.
 
 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}] [-o @var{options}] @var{filename} [@var{size}]
+@item create [-f @var{fmt}] [-b @var{backing_file}] [-F @var{backing_fmt}] [-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}
 
 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}


@@ -302,7 +311,7 @@ Error on reading data
 
 @end table
 
 
 @end table
 

-@item convert [-c] [-p] [-n] [-f @var{fmt}] [-t @var{cache}] [-T @var{src_cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_id_or_name}] [-l @var{snapshot_param}] [-m @var{num_coroutines}] [-W] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
+@item convert [-c] [-p] [-n] [-f @var{fmt}] [-t @var{cache}] [-T @var{src_cache}] [-O @var{output_fmt}] [-B @var{backing_file}] [-o @var{options}] [-s @var{snapshot_id_or_name}] [-l @var{snapshot_param}] [-m @var{num_coroutines}] [-W] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}

 
 Convert the disk image @var{filename} or a snapshot @var{snapshot_param}(@var{snapshot_id_or_name} is deprecated)
 to disk image @var{output_filename} using format @var{output_fmt}. It can be optionally compressed (@code{-c}
 
 Convert the disk image @var{filename} or a snapshot @var{snapshot_param}(@var{snapshot_id_or_name} is deprecated)
 to disk image @var{output_filename} using format @var{output_fmt}. It can be optionally compressed (@code{-c}


@@ -558,16 +567,29 @@ The use of encryption in qcow and qcow2 images is considered to be flawed by
 modern cryptography standards, suffering from a number of design problems:
 
 @itemize @minus
 modern cryptography standards, suffering from a number of design problems:
 
 @itemize @minus

-@item The AES-CBC cipher is used with predictable initialization vectors based
+@item
+The AES-CBC cipher is used with predictable initialization vectors based

 on the sector number. This makes it vulnerable to chosen plaintext attacks
 which can reveal the existence of encrypted data.
 on the sector number. This makes it vulnerable to chosen plaintext attacks
 which can reveal the existence of encrypted data.

-@item The user passphrase is directly used as the encryption key. A poorly
+@item
+The user passphrase is directly used as the encryption key. A poorly

 chosen or short passphrase will compromise the security of the encryption.
 chosen or short passphrase will compromise the security of the encryption.

-@item In the event of the passphrase being compromised there is no way to
+@item
+In the event of the passphrase being compromised there is no way to

 change the passphrase to protect data in any qcow images. The files must
 be cloned, using a different encryption passphrase in the new file. The
 original file must then be securely erased using a program like shred,
 though even this is ineffective with many modern storage technologies.
 change the passphrase to protect data in any qcow images. The files must
 be cloned, using a different encryption passphrase in the new file. The
 original file must then be securely erased using a program like shred,
 though even this is ineffective with many modern storage technologies.

+@item
+Initialization vectors used to encrypt sectors are based on the
+guest virtual sector number, instead of the host physical sector. When
+a disk image has multiple internal snapshots this means that data in
+multiple physical sectors is encrypted with the same initialization
+vector. With the CBC mode, this opens the possibility of watermarking
+attacks if the attack can collect multiple sectors encrypted with the
+same IV and some predictable data. Having multiple qcow2 images with
+the same passphrase also exposes this weakness since the passphrase
+is directly used as the key.

 @end itemize
 
 Use of qcow / qcow2 encryption is thus strongly discouraged. Users are
 @end itemize
 
 Use of qcow / qcow2 encryption is thus strongly discouraged. Users are