nbdkit-pattern-plugin - Man Page

 nbdkit pattern [size=]SIZE [stride=BLOCK_SIZE]

nbdkit-pattern-plugin is a plugin for nbdkit(1) which serves a fixed pattern of data, read only.  This is used for testing nbdkit filters and NBD clients.

To create test disks filled with other repeated patterns use nbdkit-data-plugin(1) or nbdkit-ones-plugin(1) instead.  To create disks filled with random data, use nbdkit-random-plugin(1) or nbdkit-sparse-random-plugin(1).

The fixed pattern is the offset, as a 64 bit big endian integer, every 8 bytes.  In hexadecimal this looks like:

 offset                         data
  0000:   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 08
  0010:   00 00 00 00 00 00 00 10   00 00 00 00 00 00 00 18
  0020:   00 00 00 00 00 00 00 20   00 00 00 00 00 00 00 28
                                  ↗ └──────────┬──────────┘
              byte at offset 0x28              │
                                               │
                                     64 bit big endian int
                                     encoding offset 0x28

The size of the virtual disk must be specified using the size parameter.  If the size is not a multiple of 8 then the last 8 byte offset in the pattern is truncated.

 offset                         data
  0000:   12 34 00 00 00 00 00 00   12 34 00 00 00 00 00 08
  0010:   12 34 00 00 00 00 00 10   12 34 00 00 00 00 00 18
  0020:   12 34 00 00 00 00 00 20   12 34 00 00 00 00 00 28

 offset                         data
  0000:   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00
  0010:   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00
  ...
  ...                          block at offset 0x1000 (4k)
  ...                        ↙
  1000:   00 00 00 00 00 00 10 00   00 00 00 00 00 00 00 00
  1010:   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00
  ...
  ...                          block at offset 0x2000 (8k)
  ...                        ↙
  2000:   00 00 00 00 00 00 20 00   00 00 00 00 00 00 00 00
  2010:   00 00 00 00 00 00 00 00   00 00 00 00 00 00 00 00

 nbdkit pattern size=100M --run 'nbdcopy "$uri" "$uri"'

 nbdkit pattern 9223372036854775807

 nbdkit pattern 1G --filter=swab swab-bits=64

[size=]SIZE

Specify the virtual size of the disk image.

This parameter is required.

size= prefix may be omitted in most cases. See "Magic parameters" in nbdkit(1).

stride=BLOCK_SIZE

Instead of writing the 64 bit integers sequentially, place them at the beginning of each BLOCK_SIZE block.  See "Strides" above.

The minimum, and default, stride is 8 which places the integers sequentially with no gaps.  The stride must be a power of two.

upper=N

XOR N (N=0..65535) with the top 16 bits of the pattern word.  You can prefix the value with 0x for hexadecimal.  The default is 0.

upper=random

On each run of nbdkit, a random number in the range 1..65535 (not 0) is chosen for the upper 16 bits of each word.

$plugindir/nbdkit-pattern-plugin.so

The plugin.

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

nbdkit-pattern-plugin first appeared in nbdkit 1.6.

nbdkit(1), nbdkit-plugin(3), nbdkit-checkwrite-filter(1), nbdkit-data-plugin(1), nbdkit-full-plugin(1), nbdkit-null-plugin(1), nbdkit-ones-plugin(1), nbdkit-offset-filter(1), nbdkit-random-plugin(1), nbdkit-sparse-random-plugin(1), nbdkit-swab-filter(1), nbdkit-zero-plugin(1).

Richard W.M. Jones

Copyright Red Hat

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.
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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.

nbdkit(1), nbdkit-data-plugin(1), nbdkit-full-plugin(1), nbdkit-null-plugin(1), nbdkit-ones-plugin(1), nbdkit-plugin(3), nbdkit-random-plugin(1), nbdkit-release-notes-1.14(1), nbdkit-release-notes-1.46(1), nbdkit-release-notes-1.6(1), nbdkit-sparse-random-plugin(1), nbdkit-swab-filter(1), nbdkit-zero-plugin(1).