nbdkit-qcow2dec-filter(1)

📦
version 1.48.0 · 9 versions
, in ubuntu stonking

💅 nbdkit-qcow2dec-filter(1) — decode qcow2 files (yes bestie, the manual page)

okay so first things first, the manual name is nbdkit-qcow2dec-filter and this is, like, its whole personality. let's get into it ✨

🌸 NAME 🌸

nbdkit-qcow2dec-filter — decode qcow2 files

🎀 SYNOPSIS 🎀

nbdkit --filter=qcow2dec PLUGIN

that's it. that's the whole vibe. 🫶

🦋 DESCRIPTION 🦋

nbdkit-qcow2dec-filter is a filter for nbdkit(1) that can decode some qcow2 files. lowkey iconic. you slap it on top of plugins that hand you qcow2 data — think nbdkit-file-plugin(1) or nbdkit-curl-plugin(1) — and it does its thing. for example, to expose a local qcow2 file as raw format over NBD:

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

ok but here's the thing, bestie, and i need you to hear me: this filter can only decode qcow2 files. it cannot write to them. it has other limitations too — scroll down to "LIMITATIONS" fr fr. and the NBD export will be read-only unless you stack nbdkit-cow-filter(1) on top of it. 🎀

also! qemu-nbd(8) is an alternate NBD server with native support for qcow2. just so you know your options. 💖

💀 LIMITATIONS 💀

this filter has several limitations, and ngl some of them we never intend to implement. so 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). like, always. periodt.

  • 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. that's the whole deal, no cap.
  • Versions 2 and 3 only — only qcow2 subversions 2 and 3 (a.k.a. compat=0.10 and compat=1.1) are supported. if you're on some other version… ma'am, no. 🙈
  • 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. may. 👀
  • 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. it's giving "not on the roadmap" energy. 💀

🧚 PARAMETERS 🧚

there are no parameters specific to this filter. zero. none. zip. parameters are passed through to the underlying plugin, which is honestly so chill of it. ✨

⭐ 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. a whole era. 👑

🍓 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).

(the links are right there, go read them, i believe in you 🫶)

💜 AUTHORS 💜

Richard W.M. Jones

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.

like, legally speaking, it's "AS IS" — so don't come crying to Red Hat if it breaks, that's the deal 💅

and that's the page!! this little beauty is from nbdkit-1.48.0, dated 2026-08-22 — so go forth and decode some qcow2, bestie, you've got this 💖✨🎀🦋

📦 where this page comes from