xnbd-register(8) Restore xNBD sessions upon boot


xnbd-register [OPTIONS] --start

xnbd-register [OPTIONS] --stop

xnbd-register [OPTIONS] --restart

xnbd-register [OPTIONS] --status


With the xnbd-register command one can restore xnbd-wrapper and xnbd-client sessions based on a configuration file. This is useful to start client, wrapper or both upon boot.

To achieve this, xnbd-register reads a semi-structured configuration file located in /etc/xnbd.conf. See below for format hints.


The following options are supported:


Start devices configured in the configuration files. If the configuration files describes volumes, xnbd-register will try to establish a client connection to the configured wrapper instance.

Alternatively, xnbd-register will start sharing configured volumes by starting an xnbd-wrapper super server.


Retrieve wrapper status from a running xnbd-wrapper command, if applicable.


Analogous to the start option, the stop argument will stop all xnbd connection, being client or wrapper instances.


Restart all xnbd instances, being client or wrapper

--config FILE

Config file to use. Defaults to /etc/xnbd.conf.


Do not produce verbose output


xnbd-register will read its defaults from /etc/xnbd.conf. This is a semi-structured configuration file, describing client and wrapper connections that are supposed to be restored upon start of the system.

The syntax of the file is a JSON data structure, allowing comments starting with a hash key ("#"). Two types of objects are recognized: xnbd volumes and a wrapper instance. xnbd volumes are indexed by the supposed devices name. This is, to restore /dev/nbd0 an object named "nbd0" must be configured. Valid arguments are host, name and port. So, for example, this is to configure /dev/nbd0 connecting to localhost on port 8520. If present, identify the shared device by the configured logical name:

"nbd0": {
    "host": "",
    "port": 8520,
    "name": "name"

Similarly, a wrapper instance configures an xnbd-wrapper. Valid options are:


Specifies the listening address


Specifies the listening port


Specifies the listening socket for the control channels


Specifies the log path where logging output is being redirected to


A mapping of volumes which are exported. Mapping keys are export names, mapping values are disk image paths.

"wrapper": {
    "address": "",
    "port": 8520,
    "socket": "/var/run/xnbd.ctl",
    "logpath": "/var/log/xnbd.log",
    "volumes": {
        "one": "/dev/volume",
        "two": "/dev/sdb1",
        "three": "/var/lib/image.file",


xnbd-register was written by Arno Toell ([email protected]) for the Debian GNU/Linux system.

This manual page was written by Arno Toell ([email protected]) for the Debian GNU/Linux system (but may be used by others). Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, version 2, as published by the Free Software Foundation.