XNBD-BGCTL(1) General Commands Manual XNBD-BGCTL(1)NAME
xnbd-bgctl -- Control a server running xnbd-server(8) through its control socket
SYNOPSIS
xnbd-bgctl [--cache-all] [--cache-all2] [--query] [--reconnect REMOTE_HOST REMOTE_PORT] [--shutdown] [control_socket]
DESCRIPTION
With the xmbd-bgctl command you can connect to a xnbd-server control channel and instruct it to act as directed. You may pass an argument
to the control program which is then forwarded, on your behalf, to the server instance.
OPTIONS
The following options are supported:
--cache-all
If the remote xnbd-server acts as proxy server, this command intstructs the controlling xnbd-server instance to cache all blocks
on its associated block disk. Upon completion the controlled xnbd instance holds all data from the origin instance and it is no
longer necessary to act as proxy.
--cache-all2
This command is identical to cache-all but detaches the process from the terminal and is hence using a dedicated connection for
data transfer.
--query This command retrieves completion statistics from the proxy server instance. It returns the number of cached blocks on the
server.
--reconnect
This command recovers from a lost connection by re-establishing connectivity with the origin server. This command expects two
additional arguments, the REMOTE_HOST, and the REMOTE_PORT you want to connect to, to recover from a disconnected session.
--shutdown
This command stops the proxy server and restarts the target server. All client sessions are preserved.
POSITIONAL ARGUMENTS
The following positional options are supported:
CONTROL_SOCKET
The Unix domain socket, the xnbd-server(8) program is listening on.
SEE ALSO
xnbd-server (8).
AUTHOR
The NBD kernel module and the NBD tools have been written by Pavel Macheck (pavel@ucw.cz) and is now maintained by Paul Clements.
(Paul.Clements@steeleye.com).
The xNBD userland (client and server) have been written by Takahiro Hirofuchi (t.hirofuchi@aist.go.jp)
This manual page was written by Arno Toell (debian@toell.net) for the Debian GNU/Linux system (but may be used by others). Permission is
granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, version 2, as published by the
Free Software Foundation.
XNBD-BGCTL(1)
Check Out this Related Man Page
NBD-CLIENT(8)NBD-CLIENT(8)NAME
nbd-client - connect to a server running nbd-server(1), to use its exported block device
SYNOPSIS
nbd-client [ bs=blocksize ] [ timeout=seconds ] host port nbd-device [ -sdp ] [ -swap ] [ -persist ] [ -nofork ]
nbd-client -d nbd-device
nbd-client -c nbd-device
DESCRIPTION
With nbd-client, you can connect to a server running nbd-server, thus using raw diskspace from that server as a blockdevice on the local
client.
To do this, support from the Linux Kernel is necessary, in the form of the Network Block Device (NBD). When you have that, either in the
kernel, or as a module, you can connect to an NBD server and use its exported file through a block special file with major mode 43.
OPTIONS
The following options are supported:
bs=blocksize
Use a blocksize of "blocksize". Default is 1024; allowed values are either 512, 1024, 2048 or 4096
host The hostname of the machine running nbd-server.
timeout=seconds
Set the connection timeout to "seconds". For this to work, you need a kernel with support for the NBD_SET_TIMEOUT ioctl; this was
introduced into Linus' tree on 2007-10-11, and will be part of kernel 2.6.24.
port The TCP port on which nbd-server is running at the server.
nbd-device
The block special file this nbd-client should connect to.
-c Check whether the specified nbd device is connected.
If the device is connected, nbd-client will exit with an exit state of 0 and print the PID of the nbd-client instance that connected
it to stdout.
If the device is not connected or does not exist (for example because the nbd module was not loaded), nbd-client will exit with an
exit state of 1 and not print anything on stdout.
If an error occurred, nbd-client will exit with an exit state of 2, and not print anything on stdout either.
-d Disconnect the specified nbd device from the server
-persist
When this option is specified, nbd-client will immediately try to reconnect an nbd device if the connection ever drops unexpectedly
due to a lost server or something similar.
-sdp Connect to the server using the Socket Direct Protocol (SDP), rather than IP. See nbd-server(1) for details.
-swap Specifies that this NBD device will be used as swapspace. This option attempts to prevent deadlocks by performing mlockall() at an
appropriate time. It does not however guarantee that such deadlocks can be avoided.
-nofork
Specifies that the NBD client should not detach and daemonize itself. This is mostly useful for debugging.
EXAMPLES
Some examples of nbd-client usage:
o To connect to a server running on port 2000 at host "server.domain.com", using the client's block special file "/dev/nb0":
nbd-client server.domain.com 2000 /dev/nb0
o To connect to a server running on port 2001 at host "swapserver.domain.com", using the client's block special file "/dev/nb1", for swap
purposes:
nbd-client swapserver.domain.com 2001 /dev/nb1 -swap
o To disconnect the above connection again (after making sure the block special file is not in use anymore):
nbd-client -d /dev/nb1
SEE ALSO
nbd-server (1).
AUTHOR
The NBD kernel module and the NBD tools have been written by Pavel Macheck (pavel@ucw.cz).
The kernel module is now maintained by Paul Clements (Paul.Clements@steeleye.com), while the userland tools are maintained by Wouter Ver-
helst (wouter@debian.org)
This manual page was written by Wouter Verhelst (<wouter@debian.org>) for the Debian GNU/Linux system (but may be used by others). Permis-
sion is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, version 2, as published
by the Free Software Foundation.
26 May 2009 NBD-CLIENT(8)