DOKK / manpages / debian 10 / nbdkit / nbdkit-pattern-plugin.1.en
nbdkit-pattern-plugin(1) NBDKIT nbdkit-pattern-plugin(1)

nbdkit-pattern-plugin - plugin to serve a fixed pattern of data for testing

 nbdkit pattern size=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.

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.

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 size=9223372036854775807

Note this is too large for qemu to open.

Specify the virtual size of the disk image.

This parameter is required.

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-zero-plugin(1).

Richard W.M. Jones

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2019-01-26 nbdkit-1.10.3