1nbdkit-memory-plugin(1) NBDKIT nbdkit-memory-plugin(1)
2
6 nbdkit-memory-plugin - nbdkit virtual memory (RAM disk) plugin
7
9 nbdkit memory size=SIZE
10
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.
16 All nbdkit clients will see the same disk content, initially all
18 zeroes.
19 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.
25 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.
30 Preloading small amounts of data
32 If you want an in-memory disk image preinitialized with a small amount
33 of data specified on the command line, look at nbdkit-data-plugin(1)
34 instead. Note by "small" this does not mean that the virtual disk
35 image must be small, but that the amount of data initially stored
36 sparsely is small enough to specify on the command line.
37 Preloading large amounts of data
39 If you want to preload a large amount of data (eg. a disk image) into
40 the memory plugin, use qemu-img(1):
41 $ rm -f pid
43 $ nbdkit -P pid memory size=10G
44 # wait for nbdkit to become ready to accept connections:
46 $ while [ ! -f pid ]; do sleep 1; done
47 # preload Fedora disk image:
49 $ virt-builder fedora-28 --size=10G
50 $ qemu-img convert -p -n fedora-28.img nbd:localhost:10809
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53 size=SIZE
54 Specify the virtual size of the disk image.
55 This parameter is required.
57
59 nbdkit(1), nbdkit-plugin(3), nbdkit-data-plugin(1),
60 nbdkit-file-plugin(1).
61
63 Richard W.M. Jones
64
66 Copyright (C) 2017-2018 Red Hat Inc.
67
69 Redistribution and use in source and binary forms, with or without
70 modification, are permitted provided that the following conditions are
71 met:
72 · Redistributions of source code must retain the above copyright
74 notice, this list of conditions and the following disclaimer.
75 · Redistributions in binary form must reproduce the above copyright
77 notice, this list of conditions and the following disclaimer in the
78 documentation and/or other materials provided with the
79 distribution.
80 · Neither the name of Red Hat nor the names of its contributors may
82 be used to endorse or promote products derived from this software
83 without specific prior written permission.
84 THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
86 EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
87 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
88 PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
89 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
90 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
91 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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93 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
94 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
95 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
96nbdkit-1.12.3 2019-05-21 nbdkit-memory-plugin(1)