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nbddump(1) LIBNBD nbddump(1)

NAME

nbddump - hexdump the content of a disk over NBD

SYNOPSIS

 nbddump NBD

"NBD" is an NBD URI or subprocess:

 NBD := nbd://... | nbd+unix:// (or other URI formats)
      | [ CMD ARGS ... ]


 nbddump --help


 nbddump --version

DESCRIPTION

nbddump prints the content of a disk from an NBD server using the usual hexdump format:

 $ nbddump nbd://localhost
 0000: 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │················│
 0010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │················│
 ☆
 0100: 68 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21 00 00 00 │hello, world!···│
 0110: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │················│
 ☆
 1000: 00 00 00 21                                     │···!            │

Output format

The first field (before the ":") is the offset within the file, in hexadecimal.

The second field shows the hex codes of bytes read from the file.

The third field shows the ASCII equivalent characters (if printable).

A splat character ("☆") indicates lines of repeated output which have been squashed. (Note this is not just for lines of zero bytes, but any case where the next line shown would be the same as the previous line.)

Subprocess

nbddump can also run an NBD server as a subprocess. This requires an NBD server which understands systemd socket activation, such as qemu-nbd(8) or nbdkit(1).

For example, to dump out a qcow2 file as raw data:

 $ nbddump -- [ qemu-nbd -r -f qcow2 file.qcow2 ]

To dump out an empty floppy disk created by nbdkit-floppy-plugin(1):

 $ mkdir /var/tmp/empty
 $ nbddump -- [ nbdkit floppy /var/tmp/empty ]
 0000: 00 00 00 4d 53 57 49 4e 34 2e 31 00 00 00 00 00 |...MSWIN4.1.....|
 0010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
 ☆
 01b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fe |................|
 01c0: ff ff 0c fe ff ff 00 08 00 00 80 00 00 00 00 00 |................|

To dump out some test data using nbdkit-data-plugin(1):

 $ nbddump -- [ nbdkit data ' @0x1000 "hello!" ' ]
 0000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │················│
 ☆
 1000: 68 65 6c 6c 6f 21                               │hello!          │

Note that "[ ... ]" are separate parameters, and must be surrounded by spaces. "--" separates nbddump parameters from subprocess parameters.

OPTIONS

Display brief command line help and exit.
Enable or disable ANSI colours in output. By default we use colours if the output seems to be a terminal, and disable them if not.
Dump up to N bytes and then stop.
Display the package name and version and exit.

SEE ALSO

libnbd(3), nbdcopy(1), nbdfuse(1), nbdinfo(1), nbdsh(1), hexdump(1), file(1), qemu-img(1), nbdkit(1), qemu-nbd(8).

AUTHORS

Richard W.M. Jones

COPYRIGHT

Copyright Red Hat

LICENSE

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

2024-10-18 libnbd-1.20.3