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

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