QEMU-NBD.8(8)

NAME
qemu-nbd - QEMU Disk Network Block Device Server

SYNOPSIS
qemu-nbd [OPTION]... filename

qemu-nbd -d dev

DESCRIPTION
Export a QEMU disk image using the NBD protocol.

OPTIONS
filename is a disk image filename, or a set of block driver options if --image-opts is specified.

dev is an NBD device.

--object type,id=id,...props...
    Define a new instance of the type object class identified by id. See the qemu(1) manual page for full details of the properties supported. The common object types that it makes sense to define are the "secret" object, which is used to supply passwords and/or encryption keys, and the "tls-creds" object, which is used to supply TLS credentials for the qemu-nbd server.

-p, --port=port
    The TCP port to listen on (default 10809)

-o, --offset=offset
    The offset into the image

-b, --bind=iface
    The interface to bind to (default 0.0.0.0)

-k, --socket=path
    Use a unix socket with path path

--image-opts
    Treat filename as a set of image options, instead of a plain filename. If this flag is specified, the -f flag should not be used, instead the '"format="' option should be set.

-f, --format=fmt
    Force the use of the block driver for format fmt instead of auto-detecting

-r, --read-only
    Export the disk as read-only

-P, --partition=num
    Only expose partition num

-s, --snapshot
    Use filename as an external snapshot, create a temporary file with backing_file=filename, redirect the write to the temporary one

-l, --load-snapshot=snapshot_param
    Load an internal snapshot inside filename and export it as an read-only device, snapshot_param format is 'snapshot.id=[ID],snapshot.name=[NAME]' or '[ID_OR_NAME]'

-n, --nocache
--cache=cache
    The cache mode to be used with the file. See the documentation of the emulator's "-drive cache=..." option for allowed values.

--aio=aio
    Set the asynchronous I/O mode between threads (the default) and native (Linux only).

--discard=discard
    Control whether discard (also known as trim or unmap) requests are ignored or passed to the filesystem. discard is one of ignore (or off), unmap (or on). The default is ignore.

--detect-zeroes=detect-zeroes
    Control the automatic conversion of plain zero writes by the OS to driver-specific optimized zero write commands. detect-zeroes is one of off, on or unmap. unmap converts a zero write to an unmap operation and can only be used if discard is set to unmap. The default is off.

-c, --connect=dev
    Connect filename to NBD device dev

-d, --disconnect
    Disconnect the device dev

-e, --shared=num
    Allow up to num clients to share the device (default 1)

-t, --persistent
    Don't exit on the last connection

-x, --export-name=name
    Set the NBD volume export name. This switches the server to use the new style NBD protocol negotiation

-D, --description=description
    Set the NBD volume export description, as a human-readable string. Requires the use of -x

--tls-creds=ID
    Enable mandatory TLS encryption for the server by setting the ID of the TLS credentials object previously created with the --object option.

--fork
    Fork off the server process and exit the parent once the server is running.

-v, --verbose
    Display extra debugging information

-h, --help
    Display this help and exit

-V, --version
    Display version information and exit

-T, --trace [[enable=]pattern][,events=file][,file=file]
    Specify tracing options.

    [enable=]pattern
        Immediately enable events matching pattern (either event name or a globbing pattern). This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend. To specify multiple events or patterns, specify the -trace option multiple times.

        Use "-trace help" to print a list of names of trace points.

    events=file
        Immediately enable events listed in file. The file must contain one event name (as listed in the trace-events-all file) per line; globbing patterns are accepted too. This option is only available if QEMU has been compiled with the simple, log or ftrace tracing backend.

    file=file
        Log output traces to file. This option is only available if QEMU has been compiled with the simple tracing backend.

SEE ALSO
qemu(1), qemu-img(1)

AUTHOR
Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.