1nbdkit-nozero-filter(1)             NBDKIT             nbdkit-nozero-filter(1)
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NAME

6       nbdkit-nozero-filter - nbdkit nozero filter
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SYNOPSIS

9        nbdkit --filter=nozero plugin [zeromode=MODE] [plugin-args...]
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DESCRIPTION

12       "nbdkit-nozero-filter" is a filter that intentionally disables
13       efficient handling of sparse file holes (ranges of all-zero bytes)
14       across the NBD protocol.  It is mainly useful for evaluating timing
15       differences between naive vs. sparse-aware connections, and for testing
16       client or server fallbacks.
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PARAMETERS

19       zeromode=none|emulate
20           Optional, controls which mode the filter will use.  Mode none
21           (default) means that zero support is not advertised to the client;
22           mode emulate means that zero support is emulated by the filter
23           using the plugin's "pwrite" callback, regardless of whether the
24           plugin itself implemented the "zero" callback with a more efficient
25           way to write zeroes.
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EXAMPLES

28       Serve the file disk.img, but force the client to write zeroes
29       explicitly rather than with "NBD_CMD_WRITE_ZEROES":
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31        nbdkit --filter=nozero file disk.img
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33       Serve the file disk.img, allowing the client to take advantage of less
34       network traffic via "NBD_CMD_WRITE_ZEROES", but still forcing the data
35       to be written explicitly rather than punching any holes:
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37        nbdkit --filter=nozero file zeromode=emulate disk.img
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SEE ALSO

40       nbdkit(1), nbdkit-file-plugin(1), nbdkit-filter(3),
41       nbdkit-noextents-filter(1).
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AUTHORS

44       Eric Blake
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47       Copyright (C) 2018 Red Hat Inc.
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LICENSE

50       Redistribution and use in source and binary forms, with or without
51       modification, are permitted provided that the following conditions are
52       met:
53
54       ·   Redistributions of source code must retain the above copyright
55           notice, this list of conditions and the following disclaimer.
56
57       ·   Redistributions in binary form must reproduce the above copyright
58           notice, this list of conditions and the following disclaimer in the
59           documentation and/or other materials provided with the
60           distribution.
61
62       ·   Neither the name of Red Hat nor the names of its contributors may
63           be used to endorse or promote products derived from this software
64           without specific prior written permission.
65
66       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
67       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
68       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
69       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
70       LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
71       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
72       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
73       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
74       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
75       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
76       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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80nbdkit-1.12.3                     2019-05-21           nbdkit-nozero-filter(1)
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