DOKK / manpages / debian 13 / nbdkit / nbdkit-blkio-plugin.1.en
nbdkit-blkio-plugin(1) NBDKIT nbdkit-blkio-plugin(1)

nbdkit-blkio-plugin - libblkio plugin for NVMe, vhost-user, vDPA, VFIO

 nbdkit blkio [driver=]DRIVER [path=FILENAME] [num-queues=N] ...

nbdkit-blkio-plugin is an nbdkit(1) plugin for using libblkio to access various disk sources used for high performance applications and virtualization. These include: NVMe, vhost-user, vDPA and VFIO.

The first parameter after the plugin name should be the libblkio driver. For example:

 nbdkit blkio virtio-blk-vhost-user path=vhost.sock
          │              │               │
        plugin         driver       other parameters


 nbdkit blkio nvme-io_uring path=/dev/ng0n1

Connect to an NVMe device, issuing commands through Linux io_uring (requires Linux ≥ 5.19).

Driver: "virtio-blk-vfio-pci"

 nbdkit blkio virtio-blk-vfio-pci path=/sys/bus/pci/devices/0000:00:01.0

Connect to a PCI device which implements virtio-blk using VFIO. The path is the path to the device's sysfs directory (see lspci(8)).

Driver: "virtio-blk-vhost-user"

 nbdkit blkio virtio-blk-vhost-user path=vhost.sock

Connect to a vhost-user block device, such as one exported by qemu-storage-daemon(1). The path is the vhost-user Unix domain socket. For example:

 qemu-storage-daemon \
    --blockdev driver=file,node-name=file,filename=disk.qcow2 \
    --blockdev driver=qcow2,node-name=qcow2,file=file \
    --export type=vhost-user-blk,id=export,addr.type=unix,addr.path=vhost.sock,node-name=qcow2,writable=on

Driver: "virtio-blk-vhost-vdpa"

 nbdkit blkio virtio-blk-vhost-vdpa path=chardev

Connect to a vDPA device which might be implemented in software (eg. VDUSE) or hardware. The path is the vhost-vdpa character device.

 nbdkit blkio io_uring path=FILENAME

You can use this driver to access local files and block devices through the libblkio "io_uring" driver, but it is usually faster and easier to use nbdkit-file-plugin(1).

[driver=]DRIVER
The name of the libblkio driver to use.

This parameter is required.

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

Properties such as "path", "num-entries" etc are translated to libblkio properties. Consult the libblkio documentation for a complete list.
Get (print) the value of a property after connecting. The property is fetched and printed in nbdkit debug output, so you will need to use the --verbose flag. This is useful for debugging.

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

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

"nbdkit-blkio-plugin" first appeared in nbdkit 1.34.

nbdkit-file-plugin(1), lspci(8), qemu-storage-daemon(1), https://libblkio.gitlab.io/libblkio, https://libblkio.gitlab.io/libblkio/blkio.html.

Richard W.M. Jones

Copyright Red Hat

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2025-05-25 nbdkit-1.42.3