nbdkit-pattern-plugin - Man Page

plugin to serve a fixed pattern of data for testing

Synopsis

 nbdkit pattern [size=]SIZE

Description

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) instead.

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.

Largest possible size

nbdkit itself limits plugins to 2⁶³-1 bytes (decimal: 9223372036854775807, hexadecimal: 0x7fff_ffff_ffff_ffff).

To test if NBD clients are free of bugs (not to mention nbdkit itself) you can use:

 nbdkit pattern 9223372036854775807

Note this is too large for qemu to open.

Little endian pattern

To get a little endian pattern instead of big endian apply nbdkit-swab-filter(1) on top of this plugin:

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

Parameters

[size=]SIZE

Specify the virtual size of the disk image.

This parameter is required.

size= is a magic config key and may be omitted in most cases. See “Magic parameters” in nbdkit(1).

Files

$plugindir/nbdkit-pattern-plugin.so

The plugin.

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

Version

nbdkit-pattern-plugin first appeared in nbdkit 1.6.

See Also

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

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

2020-07-18 nbdkit-1.21.19