docs/tools/qemu-img.rst

17 machine or any other process; this may destroy the image. Also, be aware that
30   Display this help and exit
68   the -h option appearing both in the above option list and this one.
82   full option string, not a plain filename. This parameter is mutually
88   a full option string, not a plain filename. This parameter is mutually
90   the *-n* parameter to skip image creation. This restriction may be relaxed
96   other QEMU processes to open it in write mode. For example, this can be used to
98   running guest.  Note that this could produce inconsistent results because of
99   concurrent metadata changes, etc. This option is only allowed when opening
134   for ``qemu-img`` to create a sparse image during conversion. This value is
184   Allow out-of-order writes to the destination. This option improves performance,
190   Try to use copy offloading to move data from source image to target. This may
209   zeros. This parameter is mutually exclusive with a destination image
268   *FILENAME*. Not all file formats support this operation.
298   Linux, this option only works if ``-t none`` or ``-t directsync`` is
301   For write tests, by default a buffer filled with zeros is written. This can be
380   garbage data when read. For this reason, ``-b`` implies ``-d`` (so that
401   By default, compare prints out a result message. This message displays
452   skipped. This is useful for formats such as ``rbd`` if the target
457   This is only recommended for preallocated devices like host devices or other
474   that enable additional features of this format.
478   this case. *BACKING_FILE* will never be modified unless you use the
488   backing file specification valid when you want to use an image created this
492   it doesn't need to be specified separately in this case.
546     shown as 0 if this information is unavailable, e.g. because there is no
556     This is shown as ``no`` if the image is dirty and will have to be
569     Further information whose structure depends on the image format.  This
577   In particular, this commands dumps the allocation state of every sector
600   not safe to parse this output format in scripts.
629   Calculate the file size required for a new image.  This information
656   been written to all sectors.  This is the maximum size that the image file can
676   *FILENAME* supports this) the backing file format is changed to
690     This is the default mode and performs a real rebase operation. The
695     In order to achieve this, any clusters that differ between
706     ``qemu-img`` uses the unsafe mode if ``-u`` is specified. In this
712     This mode is useful for renaming or moving the backing file to
718   disk images.  This can be useful when you have copied or cloned
732   At this point, ``modified.img`` can be discarded, since
739   Before using this command to shrink a disk image, you MUST use file system and
743   When shrinking images, the ``--shrink`` option must be given. This informs
747   After using this command to grow a disk image, you must use file system and
753   description in the :ref:`notes` section which values are allowed.  Using this
765   Raw disk image format (default). This format has the advantage of
778     for image by writing data to underlying storage.  This data may or
794     newer understand (this is the default). Amongst others, this includes zero
804     This option configures which compression algorithm will be used for
805     compressed clusters on the image. Note that setting this option doesn't yet
815     If this option is set to ``on``, the image is encrypted with
823       vectors based on the sector number. This makes it vulnerable to
835       using a program like shred, though even this is ineffective with
840       sector. When a disk image has multiple internal snapshots this
842       the same initialization vector. With the CBC mode, this opens
846       passphrase also exposes this weakness since the passphrase is
866     If this option is set to ``on``, reference count updates are
868     performance. This is particularly interesting with
874     This option can only be enabled if ``compat=1.1`` is specified.
877     If this option is set to ``on``, it will turn off COW of the file. It's
882     off COW is a way to mitigate this bad performance. Generally there
887     - For an empty file, add the NOCOW file attribute. That's what this
890     Note: this option is only valid to new or empty files. If there is
897     Filename where all guest data will be stored. If this option is used,
901     using this option with ``qemu-img create`` since ``qemu-img`` will create
907     If this option is set to ``on``, QEMU will always keep the external data
910     It does this by forwarding all write accesses to the qcow2 file through to
913     offset in the raw data file. This results in a read-only raw image. Writes
918     If this option is ``off``, QEMU will use the data file to store data in an
925     This option can only be enabled if ``data_file`` is set.