nbdkit-loop(1)

1nbdkit-loop(1)                      NBDKIT                      nbdkit-loop(1)
2
3
4

NAME

6       nbdkit-loop - use nbdkit with the Linux kernel client to create loop
7       devices and loop mounts
8

DESCRIPTION

10       nbdkit (server) can be used with the Linux kernel nbd (client) in a
11       loop mode allowing any of the plugins supported by nbdkit to be turned
12       into Linux block devices.
13
14       In addition to nbdkit(1) itself, the main commands you will use are:
15
16       nbd-client localhost /dev/nbd0
17           Attaches a locally running nbdkit instance to the kernel device
18           /dev/nbd0.
19
20       nbd-client -unix /tmp/socket /dev/nbd0
21           Alternative method using a Unix domain socket instead of a public
22           TCP/IP socket.  Use "nbdkit -U /tmp/socket" to serve.
23
24       nbd-client -d /dev/nbd0
25           Detaches /dev/nbd0.
26
27       nbd-client -c /dev/nbd0
28           Queries whether /dev/nbd0 is attached or not.
29
30       modprobe nbd
31           You may be need to run this command once to load the nbd client
32           kernel module.
33
34       The nbd-client(8) and modprobe(8) commands must be run as root.
35
36   Warning: Do not loop mount untrusted filesystems
37       Untrusted filesystems and untrusted disk images should not be loop
38       mounted because they could contain exploits that attack your host
39       kernel.  Use the tools from libguestfs(3) instead since it safely
40       isolates untrusted filesystems from the host.
41
42   Loop mount a filesystem from a compressed file
43       If you have a filesystem or disk image in xz-compressed format then you
44       can use nbdkit-xz-filter(1) and nbdkit-file-plugin(1) to loop mount it
45       as follows:
46
47        nbdkit --filter=xz file disk.xz
48        nbd-client localhost /dev/nbd0
49        mount /dev/nbd0p1 /mnt
50
51   Loop mount a filesystem from a web server
52       You can use nbdkit-curl-plugin(1) to loop mount a filesystem from a
53       disk image on a web server:
54
55        nbdkit [--filter=xz] curl https://example.com/disk.img
56        nbd-client localhost /dev/nbd0
57        mount /dev/nbd0p1 /mnt
58
59       Use --filter=xz if the remote image is XZ-compressed.
60
61   Create a giant btrfs filesystem
62       nbdkit is useful for testing the limits of Linux filesystems.  Using
63       nbdkit-memory-plugin(1) you can create virtual disks stored in RAM with
64       a virtual size up to 2⁶³-1 bytes, and then create filesystems on these:
65
66        nbdkit memory $(( 2**63 - 1 ))
67        nbd-client localhost /dev/nbd0
68
69       Partition the device using GPT, creating a single partition with all
70       default settings:
71
72        gdisk /dev/nbd0
73
74       Make a btrfs filesystem on the disk and mount it:
75
76        mkfs.btrfs -K /dev/nbd0p1
77        mount /dev/nbd0p1 /mnt
78
79   Inject errors into Linux devices
80       Using nbdkit-error-filter(1) you can see how Linux devices react to
81       errors:
82
83        nbdkit --filter=error \
84               memory 64M \
85               error-rate=100% error-file=/tmp/inject
86        nbd-client localhost /dev/nbd0
87        mkfs -t ext4 /dev/nbd0
88        mount /dev/nbd0 /mnt
89
90       Inject errors by touching /tmp/inject, and stop injecting errors by
91       removing this file.
92
93   Write Linux block devices in shell script
94       Using nbdkit-sh-plugin(3) you can write custom Linux block devices in
95       shell script for testing.  For example the following shell script
96       creates a disk which contains a bad sector:
97
98        #!/bin/bash -
99        case "$1" in
100            thread_model) echo parallel ;;
101            get_size) echo 64M ;;
102            pread)
103                if [ $4 -le 100000 ] && [ $(( $4+$3 )) -gt 100000 ]; then
104                    echo EIO Bad block >&2
105                    exit 1
106                else
107                    dd if=/dev/zero count=$3 iflag=count_bytes
108                fi ;;
109            *) exit 2 ;;
110        esac
111
112       Create a loop from this shell script using:
113
114        nbdkit sh ./bad-sector.sh
115        nbd-client localhost /dev/nbd0
116
117       You can then try running tests such as:
118
119        badblocks /dev/nbd0
120

AUTHORS

127       Richard W.M. Jones
128

COPYRIGHT

130       Copyright Red Hat
131

LICENSE

133       Redistribution and use in source and binary forms, with or without
134       modification, are permitted provided that the following conditions are
135       met:
136
137       •   Redistributions of source code must retain the above copyright
138           notice, this list of conditions and the following disclaimer.
139
140       •   Redistributions in binary form must reproduce the above copyright
141           notice, this list of conditions and the following disclaimer in the
142           documentation and/or other materials provided with the
143           distribution.
144
145       •   Neither the name of Red Hat nor the names of its contributors may
146           be used to endorse or promote products derived from this software
147           without specific prior written permission.
148
149       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
150       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
151       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
152       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
153       LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
154       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
155       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
156       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
157       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
158       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
159       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
160
161
162
163nbdkit-1.34.4                     2023-09-26                    nbdkit-loop(1)

NAME

DESCRIPTION

SEE ALSO

AUTHORS

COPYRIGHT

LICENSE