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| -rw-r--r-- | qapi-schema.json | 29 | ||||
| -rw-r--r-- | qemu-img.texi | 55 |
2 files changed, 84 insertions, 0 deletions
diff --git a/qapi-schema.json b/qapi-schema.json index 5d5164f9e2..2b2c8bce07 100644 --- a/qapi-schema.json +++ b/qapi-schema.json @@ -831,6 +831,35 @@ { 'enum': 'BlockDeviceIoStatus', 'data': [ 'ok', 'failed', 'nospace' ] } ## +# @BlockDeviceMapEntry: +# +# Entry in the metadata map of the device (returned by "qemu-img map") +# +# @start: Offset in the image of the first byte described by this entry +# (in bytes) +# +# @length: Length of the range described by this entry (in bytes) +# +# @depth: Number of layers (0 = top image, 1 = top image's backing file, etc.) +# before reaching one for which the range is allocated. The value is +# in the range 0 to the depth of the image chain - 1. +# +# @zero: the sectors in this range read as zeros +# +# @data: reading the image will actually read data from a file (in particular, +# if @offset is present this means that the sectors are not simply +# preallocated, but contain actual data in raw format) +# +# @offset: if present, the image file stores the data for this range in +# raw format at the given offset. +# +# Since 1.7 +## +{ 'type': 'BlockDeviceMapEntry', + 'data': { 'start': 'int', 'length': 'int', 'depth': 'int', 'zero': 'bool', + 'data': 'bool', '*offset': 'int' } } + +## # @BlockDirtyInfo: # # Block dirty bitmap information. diff --git a/qemu-img.texi b/qemu-img.texi index ad45a6d94d..43ee4eb5c4 100644 --- a/qemu-img.texi +++ b/qemu-img.texi @@ -226,6 +226,61 @@ To enumerate information about each disk image in the above chain, starting from qemu-img info --backing-chain snap2.qcow2 @end example +@item map [-f @var{fmt}] [--output=@var{ofmt}] @var{filename} + +Dump the metadata of image @var{filename} and its backing file chain. +In particular, this commands dumps the allocation state of every sector +of @var{filename}, together with the topmost file that allocates it in +the backing file chain. + +Two option formats are possible. The default format (@code{human}) +only dumps known-nonzero areas of the file. Known-zero parts of the +file are omitted altogether, and likewise for parts that are not allocated +throughout the chain. @command{qemu-img} output will identify a file +from where the data can be read, and the offset in the file. Each line +will include four fields, the first three of which are hexadecimal +numbers. For example the first line of: +@example +Offset Length Mapped to File +0 0x20000 0x50000 /tmp/overlay.qcow2 +0x100000 0x10000 0x95380000 /tmp/backing.qcow2 +@end example +@noindent +means that 0x20000 (131072) bytes starting at offset 0 in the image are +available in /tmp/overlay.qcow2 (opened in @code{raw} format) starting +at offset 0x50000 (327680). Data that is compressed, encrypted, or +otherwise not available in raw format will cause an error if @code{human} +format is in use. Note that file names can include newlines, thus it is +not safe to parse this output format in scripts. + +The alternative format @code{json} will return an array of dictionaries +in JSON format. It will include similar information in +the @code{start}, @code{length}, @code{offset} fields; +it will also include other more specific information: +@itemize @minus +@item +whether the sectors contain actual data or not (boolean field @code{data}; +if false, the sectors are either unallocated or stored as optimized +all-zero clusters); + +@item +whether the data is known to read as zero (boolean field @code{zero}); + +@item +in order to make the output shorter, the target file is expressed as +a @code{depth}; for example, a depth of 2 refers to the backing file +of the backing file of @var{filename}. +@end itemize + +In JSON format, the @code{offset} field is optional; it is absent in +cases where @code{human} format would omit the entry or exit with an error. +If @code{data} is false and the @code{offset} field is present, the +corresponding sectors in the file are not yet in use, but they are +preallocated. + +For more information, consult @file{include/block/block.h} in QEMU's +source code. + @item snapshot [-l | -a @var{snapshot} | -c @var{snapshot} | -d @var{snapshot} ] @var{filename} List, apply, create or delete snapshots in image @var{filename}. |