NAME

       nbdkit-qcow2dec-filter - decode qcow2 files

SYNOPSIS

        nbdkit --filter=qcow2dec PLUGIN

DESCRIPTION

       "nbdkit-qcow2dec-filter" is a filter for nbdkit(1) that can decode some qcow2 files.  You can use it on
       top of plugins that provide qcow2 data, such as nbdkit-file-plugin(1) or nbdkit-curl-plugin(1).  For
       example to expose a local qcow2 file as raw format over NBD:

        nbdkit -r --filter=qcow2dec file image.qcow2

       This filter can only decode qcow2 files, it cannot write to them, and it has other limitations.  See
       "LIMITATIONS" below.  The NBD export will be read-only unless you use nbdkit-cow-filter(1) on top.

       qemu-nbd(8) is an alternate NBD server with native support for qcow2.

LIMITATIONS

       This filter has several limitations, and some of them we never intend to implement.  For general qcow2
       access, especially creating and writing to qcow2 files, it is always better to use qemu and tools such as
       qemu-img(1) and qemu-nbd(8).

       Read-only
           This  filter  only supports decoding qcow2 into raw format.  You cannot write to the qcow2 file.  The
           NBD export will be read-only.

       Versions 2 and 3 only
           Only qcow2 subversions 2 and 3 (a.k.a. "compat=0.10" and "compat=1.1") are supported.

       Deflate or Zstd compression only
           The most common types of qcow2 compression are  supported  if  nbdkit  was  built  with  the  correct
           libraries.  To find out which types of compression are supported, use:

            $ nbdkit null --filter=qcow2dec --dump-plugin
            ...
            qcow2dec_deflate=yes       # printed if Deflate (zlib) is supported
            qcow2dec_zstd=yes          # printed if Zstd is supported

       No snapshots
           We may add the ability to extract an internal snapshot in future.

       No bitmaps
           It may be possible to support bitmaps in future.

       No backing files
       No dirty or corrupted qcow2 files
       No encryption
       No extended L2 entries
       No external data files
           These features are not currently supported and unlikely to be supported in future.

PARAMETERS

       There are no parameters specific to this filter.  Parameters are passed through to the underlying plugin.

FILES

       $filterdir/nbdkit-qcow2dec-filter.so
           The filter.

           Use "nbdkit --dump-config" to find the location of $filterdir.

VERSION

       "nbdkit-qcow2dec-filter" first appeared in nbdkit 1.36.

SEE ALSO

       nbdkit(1),    nbdkit-cow-filter(1),   nbdkit-curl-plugin(1),   nbdkit-file-plugin(1),   nbdkit-filter(3),
       https://github.com/qemu/qemu/blob/master/docs/interop/qcow2.txt,
       https://web.archive.org/web/20201006212750/https://people.gnome.org/~markmc/qcow-image-format-version-1.html,
       qemu-img(1), qemu-nbd(8).

AUTHORS

       Richard W.M. Jones

COPYRIGHT

       Copyright Red Hat

LICENSE

       Redistribution and use in source and binary forms, with or without modification, are  permitted  provided
       that the following conditions are met:

       •   Redistributions  of  source  code must retain the above copyright notice, this list of conditions and
           the following disclaimer.

       •   Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
           the following disclaimer in the documentation and/or other materials provided with the distribution.

       •   Neither the name of Red Hat nor the names of its contributors may  be  used  to  endorse  or  promote
           products derived from this software without specific prior written permission.

       THIS  SOFTWARE  IS  PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
       INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND  FITNESS  FOR  A  PARTICULAR
       PURPOSE  ARE  DISCLAIMED.  IN  NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
       INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,  PROCUREMENT  OF
       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
       ON  ANY  THEORY  OF  LIABILITY,  WHETHER  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
       DAMAGE.

nbdkit-1.36.3                                      2024-03-31                          nbdkit-qcow2dec-filter(1)