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.IX Title "nbdkit-qcow2dec-filter 1"
.TH nbdkit-qcow2dec-filter 1 2024-05-08 nbdkit-1.38.2 NBDKIT
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH NAME
nbdkit\-qcow2dec\-filter \- decode qcow2 files
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& nbdkit \-\-filter=qcow2dec PLUGIN
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\f(CW\*(C`nbdkit\-qcow2dec\-filter\*(C'\fR is a filter for \fBnbdkit\fR\|(1) that can decode
some qcow2 files.  You can use it on top of plugins that provide qcow2
data, such as \fBnbdkit\-file\-plugin\fR\|(1) or \fBnbdkit\-curl\-plugin\fR\|(1).
For example to expose a local qcow2 file as raw format over NBD:
.PP
.Vb 1
\& nbdkit \-r \-\-filter=qcow2dec file image.qcow2
.Ve
.PP
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 \fBnbdkit\-cow\-filter\fR\|(1) on top.
.PP
\&\fBqemu\-nbd\fR\|(8) is an alternate NBD server with native support for
qcow2.
.SH LIMITATIONS
.IX Header "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 \fBqemu\-img\fR\|(1) and \fBqemu\-nbd\fR\|(8).
.IP Read-only 4
.IX Item "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.
.IP "Versions 2 and 3 only" 4
.IX Item "Versions 2 and 3 only"
Only qcow2 subversions 2 and 3 (a.k.a. \f(CW\*(C`compat=0.10\*(C'\fR and
\&\f(CW\*(C`compat=1.1\*(C'\fR) are supported.
.IP "Deflate or Zstd compression only" 4
.IX Item "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:
.Sp
.Vb 4
\& $ nbdkit null \-\-filter=qcow2dec \-\-dump\-plugin
\& ...
\& qcow2dec_deflate=yes       # printed if Deflate (zlib) is supported
\& qcow2dec_zstd=yes          # printed if Zstd is supported
.Ve
.IP "No snapshots" 4
.IX Item "No snapshots"
We may add the ability to extract an internal snapshot in future.
.IP "No bitmaps" 4
.IX Item "No bitmaps"
It may be possible to support bitmaps in future.
.IP "No backing files" 4
.IX Item "No backing files"
.PD 0
.IP "No dirty or corrupted qcow2 files" 4
.IX Item "No dirty or corrupted qcow2 files"
.IP "No encryption" 4
.IX Item "No encryption"
.IP "No extended L2 entries" 4
.IX Item "No extended L2 entries"
.IP "No external data files" 4
.IX Item "No external data files"
.PD
These features are not currently supported and unlikely to be
supported in future.
.SH PARAMETERS
.IX Header "PARAMETERS"
There are no parameters specific to this filter.  Parameters are
passed through to the underlying plugin.
.SH FILES
.IX Header "FILES"
.ie n .IP \fR\fI$filterdir\fR\fI/nbdkit\-qcow2dec\-filter.so\fR 4
.el .IP \fR\f(CI$filterdir\fR\fI/nbdkit\-qcow2dec\-filter.so\fR 4
.IX Item "$filterdir/nbdkit-qcow2dec-filter.so"
The filter.
.Sp
Use \f(CW\*(C`nbdkit \-\-dump\-config\*(C'\fR to find the location of \f(CW$filterdir\fR.
.SH VERSION
.IX Header "VERSION"
\&\f(CW\*(C`nbdkit\-qcow2dec\-filter\*(C'\fR first appeared in nbdkit 1.36.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\fR\|(1),
\&\fBnbdkit\-cow\-filter\fR\|(1),
\&\fBnbdkit\-curl\-plugin\fR\|(1),
\&\fBnbdkit\-file\-plugin\fR\|(1),
\&\fBnbdkit\-filter\fR\|(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,
\&\fBqemu\-img\fR\|(1),
\&\fBqemu\-nbd\fR\|(8).
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP \(bu 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP \(bu 4
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.
.IP \(bu 4
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.
.PP
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.