nbdsh - Man Page

​ $ nbdsh
​
​ Welcome to nbdsh, the shell for interacting with
​ Network Block Device (NBD) servers.
​
​ The ‘nbd’ module has already been imported and there
​ is an open NBD handle called ‘h’.
​
​ nbd> h.connect_command(["nbdkit", "-s", "memory", "1G"])
​ nbd> h.get_size()
​ 1073741824
​ nbd> buf = b"hello, world"
​ nbd> h.pwrite(buf, 0)
​ nbd> exit()

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).

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

-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.

libnbd(3), ​libnbd-python(3), ​libnbd-security(3), ​nbdcopy(1), ​nbddiscard(1), ​nbddump(1), ​nbdfuse(1), ​nbdinfo(1), ​nbdublk(1), ​nbdzero(1), ​qemu-img(1), ​nbdkit(1).

Richard W.M. Jones

Copyright Red Hat

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