nbdkit-streaming-plugin man page

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.

See Also

nbdkit(1), nbdkit-plugin(3).

Authors

Richard W.M. Jones

License

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

THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Referenced By

nbdkit(1), nbdkit-plugin(3).

2018-09-18 nbdkit-1.7.3 NBDKIT