NAME

nbdkit-streaming-plugin - nbdkit streaming plugin

SYNOPSIS

 nbdkit streaming pipe=FILENAME [size=SIZE]

DESCRIPTION

"nbdkit-streaming-plugin" is a plugin for nbdkit(1) that can turn certain kinds of input into a stream.

If the NBD client opens the NBD port, and writes from the start to the end of the disk without seeking backwards, then this plugin will turn the resulting disk image into a stream of data which is written to the named "pipe" parameter.

               ┌───────────┐
 client        │ nbdkit    │        plugin streams
 writes ──────▶│ streaming │──────▶ data to pipe
               │ plugin    │
               └───────────┘

Typical usage is with qemu tools. The following command will not work because the output is a pipe or socket:

 qemu-img convert input -O raw pipe

However this will work:

 nbdkit -U - streaming pipe=pipe --run '
   qemu-img convert -n input -O raw $nbd
 '

              ┌───────────┐       ┌───────────┐
 reads        │ qemu-img  │       │ nbdkit    │        plugin streams
 input ──────▶│ convert   │──────▶│ streaming │──────▶ data to pipe
 file         │ command   │       │ plugin    │
              └───────────┘      ↑└───────────┘
                              Unix domain socket (-U -)

For use of the --run and -U - options, see nbdkit-captive(1).

PARAMETERS

pipe=FILENAME: Write to the named pipe or socket. If the pipe or socket does not exist, then it is created (as a named FIFO), otherwise the existing pipe or socket is opened and used.
This parameter is required.
size=SIZE: Specify the virtual size of the stream.
This parameter is optional. If not specified, then the virtual disk appears to the client to be very large (effectively infinite). Whether you need to specify this parameter depends on the client. Some clients don't check the size and just write/stream, others do checks or calculations based on the apparent size.

FILES

$plugindir/nbdkit-streaming-plugin.so: The plugin.
Use "nbdkit --dump-config" to find the location of $plugindir.

VERSION

"nbdkit-streaming-plugin" first appeared in nbdkit 1.2.

AUTHORS

Richard W.M. Jones

COPYRIGHT

LICENSE

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
Neither the name of Red Hat nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

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