3 @command{qemu-nbd} [OPTION]... @var{filename}
5 @command{qemu-nbd} @option{-d} @var{dev}
9 @c man begin DESCRIPTION
11 Export a QEMU disk image using the NBD protocol.
16 @var{filename} is a disk image filename, or a set of block
17 driver options if @var{--image-opts} is specified.
19 @var{dev} is an NBD device.
22 @item --object type,id=@var{id},...props...
23 Define a new instance of the @var{type} object class identified by @var{id}.
24 See the @code{qemu(1)} manual page for full details of the properties
25 supported. The common object types that it makes sense to define are the
26 @code{secret} object, which is used to supply passwords and/or encryption
27 keys, and the @code{tls-creds} object, which is used to supply TLS
28 credentials for the qemu-nbd server.
29 @item -p, --port=@var{port}
30 The TCP port to listen on (default @samp{10809})
31 @item -o, --offset=@var{offset}
32 The offset into the image
33 @item -b, --bind=@var{iface}
34 The interface to bind to (default @samp{0.0.0.0})
35 @item -k, --socket=@var{path}
36 Use a unix socket with path @var{path}
38 Treat @var{filename} as a set of image options, instead of a plain
39 filename. If this flag is specified, the @var{-f} flag should
40 not be used, instead the '@code{format=}' option should be set.
41 @item -f, --format=@var{fmt}
42 Force the use of the block driver for format @var{fmt} instead of
45 Export the disk as read-only
46 @item -P, --partition=@var{num}
47 Only expose partition @var{num}
48 @item -B, --bitmap=@var{name}
49 If @var{filename} has a qcow2 persistent bitmap @var{name}, expose
50 that bitmap via the ``qemu:dirty-bitmap:@var{name}'' context
51 accessible through NBD_OPT_SET_META_CONTEXT.
53 Use @var{filename} as an external snapshot, create a temporary
54 file with backing_file=@var{filename}, redirect the write to
56 @item -l, --load-snapshot=@var{snapshot_param}
57 Load an internal snapshot inside @var{filename} and export it
58 as an read-only device, @var{snapshot_param} format is
59 'snapshot.id=[ID],snapshot.name=[NAME]' or '[ID_OR_NAME]'
61 @itemx --cache=@var{cache}
62 The cache mode to be used with the file. See the documentation of
63 the emulator's @code{-drive cache=...} option for allowed values.
65 Set the asynchronous I/O mode between @samp{threads} (the default)
66 and @samp{native} (Linux only).
67 @item --discard=@var{discard}
68 Control whether @dfn{discard} (also known as @dfn{trim} or @dfn{unmap})
69 requests are ignored or passed to the filesystem. @var{discard} is one of
70 @samp{ignore} (or @samp{off}), @samp{unmap} (or @samp{on}). The default is
72 @item --detect-zeroes=@var{detect-zeroes}
73 Control the automatic conversion of plain zero writes by the OS to
74 driver-specific optimized zero write commands. @var{detect-zeroes} is one of
75 @samp{off}, @samp{on} or @samp{unmap}. @samp{unmap}
76 converts a zero write to an unmap operation and can only be used if
77 @var{discard} is set to @samp{unmap}. The default is @samp{off}.
78 @item -c, --connect=@var{dev}
79 Connect @var{filename} to NBD device @var{dev}
80 @item -d, --disconnect
81 Disconnect the device @var{dev}
82 @item -e, --shared=@var{num}
83 Allow up to @var{num} clients to share the device (default @samp{1})
84 @item -t, --persistent
85 Don't exit on the last connection
86 @item -x, --export-name=@var{name}
87 Set the NBD volume export name. This switches the server to use
88 the new style NBD protocol negotiation
89 @item -D, --description=@var{description}
90 Set the NBD volume export description, as a human-readable
91 string. Requires the use of @option{-x}
93 Enable mandatory TLS encryption for the server by setting the ID
94 of the TLS credentials object previously created with the --object
97 Fork off the server process and exit the parent once the server is running.
99 Display extra debugging information
101 Display this help and exit
103 Display version information and exit
104 @item -T, --trace [[enable=]@var{pattern}][,events=@var{file}][,file=@var{file}]
106 @include qemu-option-trace.texi
113 @setfilename qemu-nbd
114 @settitle QEMU Disk Network Block Device Server
117 Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>.
118 This is free software; see the source for copying conditions. There is NO
119 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.