nbdkit-cdi-plugin(1) | NBDKIT | nbdkit-cdi-plugin(1) |
nbdkit-cdi-plugin - export a layer from a container image
nbdkit cdi [name=]NAME[:TAG|@DIGEST] [layer=N]
"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.
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
"name=" is a magic config key and may be omitted in most cases. See "Magic parameters" in nbdkit(1).
Use "nbdkit --dump-config" to find the location of $plugindir.
"nbdkit-cdi-plugin" first appeared in nbdkit 1.22.
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.
Richard W.M. Jones
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2021-01-20 | nbdkit-1.24.1 |