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

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