1nbdkit-linuxdisk-plugin(1) NBDKIT nbdkit-linuxdisk-plugin(1)
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6 nbdkit-linuxdisk-plugin - create virtual Linux disk from directory
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9 nbdkit linuxdisk [dir=]DIRECTORY
10 [label=LABEL] [type=ext2|ext3|ext4]
11 [size=[+]SIZE]
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14 "nbdkit-linuxdisk-plugin" is a plugin for nbdkit(1) which creates an
15 ext2-, ext3- or ext4-formatted disk image from a directory on the fly.
16 The files in the specified directory (and subdirectories) appear in the
17 virtual disk, which is served read-only over the NBD protocol.
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19 The virtual disk is partitioned with a single GPT partition containing
20 the filesystem.
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22 The virtual disk can be used as a Linux root (or other) filesystem.
23 Most features of Linux filesystems are supported, such as hard links,
24 symbolic links, block special devices etc.
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26 To create a FAT-formatted virtual floppy disk, see
27 nbdkit-floppy-plugin(1). To create a CD/ISO, see nbdkit-iso-plugin(1).
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30 nbdkit linuxdisk /path/to/directory label=ROOTFS
31 Create a virtual disk, giving it a filesystem label. Note that
32 clients will not be able to modify the filesystem, so it is safe to
33 share it with multiple clients.
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35 nbdkit --filter=cow linuxdisk /path/to/directory
36 Add a writable overlay (see nbdkit-cow-filter(1), allowing the disk
37 to be written by the client. Multiple clients must not be allowed
38 to connect at the same time (even if they all mount it read-only)
39 as this will cause disk corruption.
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41 nbdkit --filter=cow linuxdisk /path/to/directory size=+1G
42 The same but specifying that at least 1G of free space should be
43 available in the filesystem (not including the space taken by the
44 initial filesystem).
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46 nbdkit --filter=partition linuxdisk /path/to/directory partition=1
47 Instead of serving a partitioned disk image, serve just the "naked"
48 filesystem (ie. the first partition, see
49 nbdkit-partition-filter(1)).
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51 nbdkit -U - linuxdisk /path/to/directory --run 'qemu-img convert $nbd
52 ext2fs.img'
53 This serves nothing. Instead it turns a directory into a disk
54 image, writing it to ext2fs.img (see nbdkit-captive(1)). The
55 resulting image is a partitioned disk.
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57 Create a minimal virtual appliance
58 This creates and boots a minimal busybox(1)-based virtual
59 appliance. This assumes that your kernel (/boot/vmlinuz) contains
60 the ext2 or ext4 driver compiled in, but most Linux distro kernels
61 have that.
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63 mkdir -p root/{bin,dev,proc,sbin,sys,usr/bin,usr/sbin}
64 sudo mknod root/dev/console c 5 1
65 cp /sbin/busybox root/sbin/
66 ln root/sbin/busybox root/sbin/init
67 ln root/sbin/busybox root/bin/ls
68 ln root/sbin/busybox root/bin/sh
69 nbdkit -U - linuxdisk root --run '
70 qemu-kvm -display none -kernel /boot/vmlinuz -drive file=nbd:unix:$unixsocket,snapshot=on -append "console=ttyS0 root=/dev/sda1 rw" -serial stdio
71 '
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73 You can drop any extra files you need into the root/ directory and
74 they will be copied into the appliance before boot. After booting
75 type these commands to complete the environmental setup:
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77 /sbin/busybox --install
78 mount -t proc proc /proc
79 mount -t sysfs sys /sys
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82 [dir=]DIRECTORY
83 Specify the directory containing files and subdirectories which
84 will be added to the virtual disk. Files inside this directory
85 will appear in the root directory of the virtual disk.
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87 This parameter is required.
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89 "dir=" is a magic config key and may be omitted in most cases. See
90 "Magic parameters" in nbdkit(1).
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92 label=LABEL
93 The optional label for the filesystem.
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95 size=SIZE
96 size=+SIZE
97 The total (virtual) size of the filesystem.
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99 If the "size" parameter is omitted the plugin will try to size the
100 filesystem with just enough space to contain the files and
101 directories that are initially loaded, and there will not be much
102 extra space.
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104 Using "size=SIZE" specifies the required virtual size of the whole
105 filesystem (including initial files and extra space). If this is
106 set too small for the initial filesystem then the plugin will fail
107 to start.
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109 Using "size=+SIZE" specifies the minimum free space required after
110 the initial filesystem has been loaded. (The actual free space
111 might be slightly larger).
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113 type=ext2
114 type=ext3
115 type=ext4
116 Select the filesystem type. The default is "ext2".
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119 Users and groups
120 The original file UIDs and GIDs are recreated as far as possible. Note
121 that UIDs/GIDs will likely map to different users and groups when read
122 by a virtual machine or other NBD client machine.
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125 "TMPDIR"
126 The filesystem image is stored in a temporary file located in
127 /var/tmp by default. You can override this location by setting the
128 "TMPDIR" environment variable before starting nbdkit.
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131 $plugindir/nbdkit-linuxdisk-plugin.so
132 The plugin.
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134 Use "nbdkit --dump-config" to find the location of $plugindir.
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137 "nbdkit-linuxdisk-plugin" first appeared in nbdkit 1.12.
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140 mke2fs(8), nbdkit(1), nbdkit-plugin(3), nbdkit-captive(1),
141 nbdkit-cow-filter(1), nbdkit-file-plugin(1), nbdkit-floppy-plugin(1),
142 nbdkit-iso-plugin(1), nbdkit-partition-filter(1),
143 nbdkit-partitioning-plugin(1).
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146 Richard W.M. Jones
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149 Copyright (C) 2019 Red Hat Inc.
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152 Redistribution and use in source and binary forms, with or without
153 modification, are permitted provided that the following conditions are
154 met:
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156 · Redistributions of source code must retain the above copyright
157 notice, this list of conditions and the following disclaimer.
158
159 · Redistributions in binary form must reproduce the above copyright
160 notice, this list of conditions and the following disclaimer in the
161 documentation and/or other materials provided with the
162 distribution.
163
164 · Neither the name of Red Hat nor the names of its contributors may
165 be used to endorse or promote products derived from this software
166 without specific prior written permission.
167
168 THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
169 EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
170 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
171 PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
172 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
173 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
174 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
175 BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
176 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
177 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
178 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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182nbdkit-1.18.4 2020-04-16 nbdkit-linuxdisk-plugin(1)