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=" 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-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:
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