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.TH "NBD-SERVER" "1" "04 April 2004" "" ""
.SH NAME
nbd-server \- serve a file as a block device to other computers    running the GNU/Linux(tm) or GNU/Hurd Operating    System
.SH SYNOPSIS

\fBnbd-server\fR [ \fB-c \fIthis\fB\fR ] \fB\fIport\fB\fR \fB\fIfilename\fB\fR [ \fB\fIsize\fB\fR ] [ \fB-r\fR ] [ \fB-m\fR ] [ \fB-c\fR ]

.SH "DESCRIPTION"
.PP
This manual page documents the
\fBnbd-server\fR command.
.PP
This manual page was written for the Debian GNU/Linux distribution
because the original program does not have a manual page.
.PP
\fBnbd-server\fR is the server for the Linux
Network Block Device (NBD). With NBD, a client can use a file,
exported over the network from a server, as a block device. It can
then be used for whatever purpose a normal block device (harddisk,
CD-ROM, ...) can be used for.
.PP
NBD can be usefull for diskless clients that need swapspace,
but you can also create a filesystem on it and use it as though it
were a local filesystem.
.PP
\fBnbd-server\fR implements some security
through a file called "nbd_server.allow" in the current directory.
This file must list the IP-addresses of clients that are allowed
to connect. If it does not exist, all clients are able to connect.
If the file is empty, no clients can connect.
.SH "OPTIONS"
.TP
\fBport \fR
The port the server should listen to. A valid port is
any number between 1 and 65536; if 0 is used, nbd-server
will listen on stdin (so that nbd-server can be ran from
inetd)
.TP
\fBfilename\fR
The filename of the file that should be exported. This
can be any file, including "real" blockdevices (i.e. a file
from /dev). If the filename includes the literal string
"%s", then this %s will be substituded with the IP-address
of the client trying to connect.
.TP
\fBsize\fR
The size of the block device at the client side. This
is especially usefull in conjunction with the -m
option

Can optionally be followed by one of K,k,M or
m, in which case the size will be multiplied by 1024 (K
or k) or 1048576 (M or m)
.TP
\fB-r\fR
Export the file read-only. If a client tries to write
to a read-only exported file, it will receive an error, but
the connection will stay up.
.TP
\fB-m\fR
Work with multiple files. This can be used to export
blockdevices that are larger than the maximum allowed
filesize on a given filesystem; i.e. when the filesystem
does not allow files larger than 2GB (which is true for
Linux 2.2 and below), you can use this option to store the
data in multiple files and export a larger filesystem, if
needed.
.TP
\fB-c\fR
Copy on write. When this option is provided,
write-operations are not done to the exported file, but to a
separate file. This separate file is removed when the
connection is closed, which means that serving this way will
make nbd-server slow down (especially on large block devices
with lots of writes), and that after disconnecting and
reconnecting the client or the server, all changes are
lost.
.SH "EXAMPLES"
.PP
Some examples of nbd-server usage:
.TP 0.2i
\(bu
To export a file /export/nbd/exp-bl-dev on port 2000:

\fBnbd-server 2000 /export/nbd/exp-bl-dev\fR
.TP 0.2i
\(bu
To export a the same file read-only:

\fBnbd-server 2000 /export/nbd/exp-bl-dev -r\fR
.TP 0.2i
\(bu
To export the same file read-write, but make sure
changes are lost after restarting the client or the
server:

\fBnbd-server 2000 /export/nbd/exp-bl-dev
-c\fR
.SH "FILES"
.TP
\fB\fInbd_server.allow\fB\fR
This file, which must be in the directory where
nbd-server is invoked, can contain a list of IP-addresses
for hosts that may connect to the server. Wildcards are
not allowed.
.SH "SEE ALSO"
.PP
nbd-client (8).
.SH "AUTHOR"
.PP
The NBD kernel module and the NBD tools were written by
Pavel Machek (pavel@ucw.cz)
.PP
This manual page was written by Wouter Verhelst (<wouter@debian.org>) 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 Free Documentation
License, Version 1.1 or any later version published by the Free
Software Foundation; with no Invariant Sections, no Front-Cover
Texts and no Back-Cover Texts.