nbdkit-pattern-plugin(1) NBDKIT nbdkit-pattern-plugin(1) NAME nbdkit-pattern-plugin - plugin to serve a fixed pattern of data for testing SYNOPSIS nbdkit pattern [size=]SIZE [stride=BLOCK_SIZE] DESCRIPTION "nbdkit-pattern-plugin" is a plugin for nbdkit(1) which serves a fixed pat- tern of data, read only. This is used for testing nbdkit filters and NBD clients. To create test disks filled with other repeated patterns use nbd- kit-data-plugin(1) or nbdkit-ones-plugin(1) instead. To create disks filled with random data, use nbdkit-random-plugin(1) or nbdkit-sparse-ran- dom-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 a aaaaaaaaaaaa~aaaaaaaaaaa byte at offset 0x28 a a 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 pat- tern is truncated. Upper bits The "upper" parameter can be used to set the top 16 bits of each word in the pattern. This can be used to distinguish between different instances of nbdkit-pattern-plugin, or when testing copies to ensure that different data is copied each time. For example setting "upper=0x1234" changes the pattern to: 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 The upper value is XOR-ed into the top 16 bits, the default is 0. Strides Using the "stride" parameter you can create a pattern where each block of data has a unique number. This is useful for tracking down disk corruption where blocks of data may be transposed. For example, with 4096 byte block-based storage, using "stride=4k" will produce a pattern like this: 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) ... a 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) ... a 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 Writes and testing copying Writing to the disk is possible. If you do this the plugin will check that what you are writing exactly matches what would be read at the same offset (if not, it returns EIO error). You can use this to test copying programs by making the source and destination NBD URIs be the same: nbdkit pattern size=100M --run 'nbdcopy "$uri" "$uri"' "qemu-img convert" could be used in place of nbdcopy. See also nbd- kit-checkwrite-filter(1). Largest possible size nbdkit itself limits plugins to 2a<paragraph>A^3-1 bytes (deci- mal: 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-fil- ter(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=" 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 sequen- tially 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. 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-checkwrite-filter(1), nbdkit-data-plu- gin(1), nbdkit-full-plugin(1), nbdkit-null-plugin(1), nbdkit-ones-plu- gin(1), nbdkit-offset-filter(1), nbdkit-random-plugin(1), nbd- kit-sparse-random-plugin(1), nbdkit-swab-filter(1), nbdkit-zero-plugin(1). AUTHORS Richard W.M. Jones COPYRIGHT Copyright Red Hat LICENSE Redistribution and use in source and binary forms, with or without modifi- cation, 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 no- tice, this list of conditions and the following disclaimer in the docu- mentation 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. THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EX- PRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DIS- CLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DI- RECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SER- VICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABIL- ITY, 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 DAM- AGE. nbdkit-1.46.2 2026-08-30 nbdkit-pattern-plugin(1)
NAME | SYNOPSIS | DESCRIPTION | PARAMETERS | FILES | VERSION | SEE ALSO | AUTHORS | COPYRIGHT | LICENSE
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