nbdkit-offset-filter(1)

NAME
nbdkit-offset-filter - nbdkit offset filter

SYNOPSIS
 nbdkit --filter=offset plugin offset=OFFSET range=LENGTH [plugin-args...]

DESCRIPTION
"nbdkit-offset-filter" is a filter that limits requests to the byte range "[offset .. offset+range-1]" within another plugin.

PARAMETERS

offset=OFFSET
    The start offset. The offset must be ≥ 0.

    This parameter is optional. If not given then "offset=0" is assumed.

range=LENGTH
    The length of data to serve.

    This parameter is optional. If not given then the range is served starting from the offset through to the end of the underlying file/device.

Note it is an error if the offset and/or range specify data which lies beyond the end of the underlying device. Use nbdkit-truncate-filter(1) to truncate or extend the size of plugins.

EXAMPLES

  Serve part of a file
Using nbdkit-file-plugin(1), serve the file "disk.img" starting at offset "1M". The total length served is "100M" (the underlying file must therefore be at least "101M" in length):

 nbdkit --filter=offset file disk.img offset=1M range=100M

  Serve a single partition
An easier way to do this is with nbdkit-partition-filter(1).

One way to serve a single partition from a disk is to find the start and length of the partition, eg using:

 $ parted disk.img -- unit b print
 ...
 Number  Start   End         Size        Type     File system  Flags
  1      65536B  104792575B  104727040B  primary  ext2

You can then serve the partition only using:

 nbdkit --filter=offset file disk.img offset=65536 range=104727040

FILES

$filterdir/nbdkit-offset-filter.so
    The filter.

    Use "nbdkit --dump-config" to find the location of $filterdir.

VERSION
"nbdkit-offset-filter" first appeared in nbdkit 1.2.

SEE ALSO
nbdkit(1), nbdkit-file-plugin(1), nbdkit-filter(3), nbdkit-partition-filter(1), nbdkit-protect-filter(1), nbdkit-tar-filter(1), nbdkit-truncate-filter(1).

AUTHORS
Eric Blake

Richard W.M. Jones

COPYRIGHT
Copyright (C) 2018 Red Hat Inc.

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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