nbdkit-memory-plugin(1)

1nbdkit-memory-plugin(1)             NBDKIT             nbdkit-memory-plugin(1)
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NAME

6       nbdkit-memory-plugin - nbdkit virtual memory (RAM disk) plugin
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SYNOPSIS

9        nbdkit memory [size=]SIZE
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DESCRIPTION

12       "nbdkit-memory-plugin" is a plugin for nbdkit(1) which stores a single
13       disk image in virtual memory, and discards it when nbdkit exits.  This
14       plugin can be used for testing or where you don't care about the final
15       content of the disk image.
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17       All nbdkit clients will see the same disk content, initially all
18       zeroes.
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20       The disk image is stored in memory using a sparse array.  The allocated
21       parts of the disk image cannot be larger than physical RAM plus swap,
22       less whatever is being used by the rest of the system.  If you want to
23       allocate more space than this use nbdkit-file-plugin(1) backed by a
24       temporary file instead.
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26       However the virtual size can be as large as you like, up to the maximum
27       supported by nbdkit (2⁶³-1 bytes).  This limit is tested when nbdkit is
28       compiled, and it should work on all platforms and architectures
29       supported by nbdkit.
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EXAMPLES

32       Create a one gigabyte sparse RAM disk:
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34        nbdkit memory 1G
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36       If you want to loop mount the above disk, see nbdkit-loop(1).
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38       Create the largest possible RAM disk:
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40        nbdkit memory $(( 2**63 - 1 ))
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PARAMETERS

43       [size=]SIZE
44           Specify the virtual size of the disk image.
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46           This parameter is required.
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48           "size=" is a magic config key and may be omitted in most cases.
49           See "Magic parameters" in nbdkit(1).
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NOTES

52   Preloading small amounts of data
53       If you want an in-memory disk image preinitialized with a small amount
54       of data specified on the command line, look at nbdkit-data-plugin(1)
55       instead.  Note by "small" this does not mean that the virtual disk
56       image must be small, but that the amount of data initially stored
57       sparsely is small enough to specify on the command line.
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59   Preloading large amounts of data
60       If you want to preload a large amount of data (eg. a disk image) into
61       the memory plugin, use qemu-img(1):
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63        $ rm -f pid
64        $ nbdkit -P pid memory 10G
65
66        # wait for nbdkit to become ready to accept connections:
67        $ while [ ! -f pid ]; do sleep 1; done
68
69        # preload Fedora disk image:
70        $ virt-builder fedora-28 --size=10G
71        $ qemu-img convert -p -n fedora-28.img nbd:localhost:10809
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FILES

74       $plugindir/nbdkit-memory-plugin.so
75           The plugin.
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77           Use "nbdkit --dump-config" to find the location of $plugindir.
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VERSION

80       "nbdkit-memory-plugin" first appeared in nbdkit 1.2.
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AUTHORS

87       Richard W.M. Jones
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COPYRIGHT

90       Copyright (C) 2017-2018 Red Hat Inc.
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LICENSE

93       Redistribution and use in source and binary forms, with or without
94       modification, are permitted provided that the following conditions are
95       met:
96
97       ·   Redistributions of source code must retain the above copyright
98           notice, this list of conditions and the following disclaimer.
99
100       ·   Redistributions in binary form must reproduce the above copyright
101           notice, this list of conditions and the following disclaimer in the
102           documentation and/or other materials provided with the
103           distribution.
104
105       ·   Neither the name of Red Hat nor the names of its contributors may
106           be used to endorse or promote products derived from this software
107           without specific prior written permission.
108
109       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
110       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
111       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
112       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
113       LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
114       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
115       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
116       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
117       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
118       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
119       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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123nbdkit-1.16.1                     2019-12-03           nbdkit-memory-plugin(1)