nbdkit-cdi-plugin(1)

NAME
nbdkit-cdi-plugin - export a layer from a container image

SYNOPSIS
 nbdkit cdi [name=]NAME[:TAG|@DIGEST] [layer=N]

DESCRIPTION
"nbdkit-cdi-plugin" (Containerized Data Importer plugin) is a plugin for nbdkit(1) which downloads a container image using podman-pull(1) and makes a single layer available over NBD. The plugin is essentially a convenient wrapper around podman(1) and jq(1) and requires both tools to be installed.

EXAMPLES
Given a Containerized Data Importer (CDI) registry image containing a VM disk, you can export the whole layer using:

 $ nbdkit cdi quay.io/kubevirt/fedora-cloud-container-disk-demo

The layer exported over NBD is a tar file:

 $ nbdcopy nbd://localhost - | file -
 -: POSIX tar archive

To export only the VM disk image in this layer, combine this plugin with nbdkit-tar-filter(1). In the example below the file exposed inside the tar archive is a qcow2 image so you can turn it into a raw NBD export of the virtual machine using nbdkit-qcow2dec-filter(1):

 ┌──────────────────────────────────────────┐
 │ fedora-cloud-container-disk-demo layer=0 │
 │ (uncompressed tar file)                  │
 │ ┌──────────────────────────────────────┐ │
 │ │ ./disk/downloaded                    │ │
 │ │ (qcow2 image)                        │ │
 │ └──────────────────────────────────────┘ │
 └──────────────────────────────────────────┘

 $ nbdkit cdi \
         --filter=qcow2dec \
         --filter=tar tar-entry=./disk/downloaded \
         quay.io/kubevirt/fedora-cloud-container-disk-demo \
         --run 'nbdinfo "$uri"'
 export="":
     export-size: 4294967296 (4G)
     content: DOS/MBR boot sector
 [...]

PARAMETERS

[name=]NAME[:TAG|@DIGEST]
    The name or URI of the container image. This is passed to podman-pull(1).

    "name=" prefix may be omitted in most cases. See "Magic parameters" in nbdkit(1).

layer=N
    Export the N'th layer (instead of layer 0).

ENVIRONMENT VARIABLES

"TMPDIR"
    A temporary copy of the layer is created in "TMPDIR". If this environment variable is not set then /var/tmp is used instead.

FILES

$plugindir/nbdkit-cdi-plugin.so
    The plugin.

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

VERSION
"nbdkit-cdi-plugin" first appeared in nbdkit 1.22.

SEE ALSO
nbdkit(1), nbdkit-plugin(3), nbdkit-qcow2dec-filter(1), nbdkit-tar-filter(1), podman(1), podman-pull(1), jq(1), https://github.com/kubevirt/containerized-data-importer/blob/master/doc/image-from-registry.md.

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.

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