nbdsh1

Usage

Overview

nbdsh is a Python-based interactive shell for accessing Network Block Device (NBD) servers.

For documentation about the libnbd API please open the shell and type:

 help(nbd)

For an introduction to using libnbd from Python see libnbd-python(3).

Examples

There are other example scripts in the libnbd source repository under sh/examples or see https://gitlab.com/nbdkit/libnbd/tree/master/sh/examples.

 $ nbdsh -u nbd://localhost -c 'print(h.get_size())'
 1073741824

 nbdsh -c - <<'EOF'
 from subprocess import *
 h.connect_uri("nbd://localhost")
 bootsect = h.pread(512, 0)
 p = Popen("hexdump -C", shell=True, stdin=PIPE)
 p.stdin.write(bootsect)
 EOF

 $ nbdkit memory 4096
 $ nbdsh -u nbd://localhost -c 'h.pwrite(b"\x55\xAA" * 1024, 0x400)'
 $ nbddump nbd://localhost
 0000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │················│
 ☆
 0400: 55 aa 55 aa 55 aa 55 aa 55 aa 55 aa 55 aa 55 aa │U·U·U·U·U·U·U·U·│
 ☆
 0c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │················│
 ☆
 0ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 │················│
 $ killall nbdkit

Options

-h

--help

Display brief command line help and exit.

--base-allocation

Request the use of the "base:allocation" meta context, which is the most common context used with nbd_block_status_64(3). This is equivalent to calling "h.set_meta_context(nbd.CONTEXT_BASE_ALLOCATION)" in the shell prior to connecting, and works even when combined with "--uri" (while attempting the same with "-c" would be too late).

-c 'COMMAND ...'

--command 'COMMAND ...'

Instead of starting an interactive shell, run a command. This option can be specified multiple times in order to run multiple commands.

-c -

--command -

Read standard input and execute it as a command.

-n

Do not create the implicit handle "h".

--opt-mode

Request that option mode be enabled, which gives fine-grained control over option negotiation after initially contacting the server but prior to actually using the export. This is equivalent to calling "h.set_opt_mode(True)" in the shell prior to connecting, and works even when combined with "--uri" (while attempting the same with "-c" would be too late).

-u URI

--uri URI

Connect to the given NBD URI. This is equivalent to the "h.connect_uri(URI)" command in the shell.

Note that the connection is created prior to processing any "-c" commands, which prevents the use of configuration commands such as "h.add_meta_context("NAME")" from the command line when mixed with this option. The options "--opt-mode" and "--base-allocation" can be used to make this situation easier to manage.

-v

--verbose

Enable verbose libnbd messages. This has the same effect as setting the environment variable "LIBNBD_DEBUG=1"

-V

--version

Display the package name and version and exit.