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:
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