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 docker://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 this example when you run file(1) on the tar entry within the layer it shows that it is a QCOW2 file:

 $ nbdkit cdi docker://kubevirt/fedora-cloud-container-disk-demo \
         --filter=tar tar-entry=./disk/downloaded \
         --run 'nbdcopy "$uri" - | file -'
 -: QEMU QCOW2 Image (v2), 4294967296 bytes

PARAMETERS

[name=]NAME[:TAG|@DIGEST]

The name or URI of the container image. This is passed to podman-pull(1).

"name=" is a magic config key and 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-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 (C) 2020 Red Hat Inc.

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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