1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
|
=head1 NAME
nbdkit-linuxdisk-plugin - create virtual Linux disk from directory
=head1 SYNOPSIS
nbdkit linuxdisk [dir=]DIRECTORY
[label=LABEL] [type=ext2|ext3|ext4]
[size=[+]SIZE]
=head1 DESCRIPTION
C<nbdkit-linuxdisk-plugin> is a plugin for L<nbdkit(1)> which creates
an ext2-, ext3- or ext4-formatted disk image from a directory on the
fly. The files in the specified directory (and subdirectories) appear
in the virtual disk, which is served read-only over the NBD protocol.
The virtual disk is partitioned with a single GPT partition containing
the filesystem.
The virtual disk can be used as a Linux root (or other) filesystem.
Most features of Linux filesystems are supported, such as hard links,
symbolic links, block special devices etc.
To create a FAT-formatted virtual floppy disk, see
L<nbdkit-floppy-plugin(1)>. To create a CD/ISO, see
L<nbdkit-iso-plugin(1)>. To create an empty filesystem for each
client that connects (like a "remote tmpfs") use
L<nbdkit-tmpdisk-plugin(1)>.
=head1 EXAMPLES
=over 4
=item nbdkit linuxdisk /path/to/directory label=ROOTFS
Create a virtual disk, giving it a filesystem label. Note that
clients will not be able to modify the filesystem, so it is safe to
share it with multiple clients.
=item nbdkit --filter=cow linuxdisk /path/to/directory
Add a writable overlay (see L<nbdkit-cow-filter(1)>, allowing the disk
to be written by the client. B<Multiple clients must not be allowed
to connect at the same time> (even if they all mount it read-only) as
this will cause disk corruption.
=item nbdkit --filter=cow linuxdisk /path/to/directory size=+1G
The same but specifying that at least 1G of free space should be
available in the filesystem (not including the space taken by the
initial filesystem).
=item nbdkit --filter=partition linuxdisk /path/to/directory partition=1
Instead of serving a partitioned disk image, serve just the "naked"
filesystem (ie. the first partition, see
L<nbdkit-partition-filter(1)>).
=item nbdkit linuxdisk /path/to/directory
--run 'nbdcopy "$uri" ext2fs.img'
This serves nothing. Instead it turns a directory into a disk image,
writing it to F<ext2fs.img> (see L<nbdkit-captive(1)>). The resulting
image is a partitioned disk.
=item Create a minimal virtual appliance
This creates and boots a minimal L<busybox(1)>-based virtual
appliance. This assumes that your kernel (F</boot/vmlinuz>) contains
the ext2 or ext4 driver compiled in, but most Linux distro kernels
have that.
mkdir -p root/{bin,dev,proc,sbin,sys,usr/bin,usr/sbin}
sudo mknod root/dev/console c 5 1
cp /sbin/busybox root/sbin/
ln root/sbin/busybox root/sbin/init
ln root/sbin/busybox root/bin/ls
ln root/sbin/busybox root/bin/sh
nbdkit linuxdisk root --run '
qemu-kvm -display none -kernel /boot/vmlinuz -drive file=nbd:unix:$unixsocket,snapshot=on -append "console=ttyS0 root=/dev/sda1 rw" -serial stdio
'
You can drop any extra files you need into the F<root/> directory and
they will be copied into the appliance before boot. After booting
type these commands to complete the environmental setup:
/sbin/busybox --install
mount -t proc proc /proc
mount -t sysfs sys /sys
=back
=head1 PARAMETERS
=over 4
=item [B<dir=>]DIRECTORY
Specify the directory containing files and subdirectories which will
be added to the virtual disk. Files inside this directory will appear
in the root directory of the virtual disk.
This parameter is required.
C<dir=> __IS_MAGIC__
=item B<label=>LABEL
The optional label for the filesystem.
=item B<size=>SIZE
=item B<size=+>SIZE
The total (virtual) size of the filesystem.
If the C<size> parameter is omitted the plugin will try to size the
filesystem with just enough space to contain the files and directories
that are initially loaded, and there will not be much extra space.
Using C<size=SIZE> specifies the required virtual size of the whole
filesystem (including initial files and extra space). If this is set
too small for the initial filesystem then the plugin will fail to
start.
Using C<size=+SIZE> specifies the minimum free space required after
the initial filesystem has been loaded. (The actual free space might
be slightly larger).
=item B<type=ext2>
=item B<type=ext3>
=item B<type=ext4>
Select the filesystem type. The default is C<ext2>.
=back
=head1 NOTES
=head2 Users and groups
The original file UIDs and GIDs are recreated as far as possible.
Note that UIDs/GIDs will likely map to different users and groups when
read by a virtual machine or other NBD client machine.
=head1 ENVIRONMENT VARIABLES
=over 4
=item C<TMPDIR>
The filesystem image is stored in a temporary file located in
F</var/tmp> by default. You can override this location by setting the
C<TMPDIR> environment variable before starting nbdkit.
=back
=head1 FILES
=over 4
=item F<$plugindir/nbdkit-linuxdisk-plugin.so>
The plugin.
Use C<nbdkit --dump-config> to find the location of C<$plugindir>.
=back
=head1 VERSION
C<nbdkit-linuxdisk-plugin> first appeared in nbdkit 1.12.
=head1 SEE ALSO
L<mke2fs(8)>,
L<nbdkit(1)>,
L<nbdkit-plugin(3)>,
L<nbdkit-captive(1)>,
L<nbdkit-cow-filter(1)>,
L<nbdkit-file-plugin(1)>,
L<nbdkit-floppy-plugin(1)>,
L<nbdkit-iso-plugin(1)>,
L<nbdkit-partition-filter(1)>,
L<nbdkit-partitioning-plugin(1)>,
L<nbdkit-tmpdisk-plugin(1)>,
=head1 AUTHORS
Richard W.M. Jones
=head1 COPYRIGHT
Copyright Red Hat
|
