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.\"	from: @(#)tftpd.8	6.7 (Berkeley) 5/13/91
.\"	$Id: tftpd.8,v 1.14 2000/07/30 23:57:10 dholland Exp $
.\"
.Dd July 29, 2000
.Dt TFTPD 8
.Os "Linux NetKit (0.17)"
.Sh NAME
.Nm tftpd
.Nd
.Tn DARPA
Trivial File Transfer Protocol server
.Sh SYNOPSIS
.Nm tftpd
.Op Fl n
.Op Fl s
.Op Ar directory ...
.Sh DESCRIPTION
.Nm Tftpd
is a server which supports the
.Tn DARPA
Trivial File Transfer
Protocol.
The
.Tn TFTP
server operates
at the port indicated in the
.Ql tftp
service description;
see
.Xr services 5 .
The server is normally started by
.Xr inetd 8 .
.Pp
The use of
.Xr tftp 1
does not require an account or password on the remote system.
Due to the lack of authentication information, 
.Nm tftpd
will allow only publicly readable files to be
accessed.
Files may be written only if they already exist and are publicly writable.
Note that this extends the concept of
.Dq public
to include
all users on all hosts that can be reached through the network;
this may not be appropriate on all systems, and its implications
should be considered before enabling tftp service.
The server should have the user ID with the lowest possible privilege.
.Pp
Access to files may be controlled by invoking
.Nm tftpd
with a list of directories by including pathnames
as server program arguments in
.Pa /etc/inetd.conf .
In this case access is restricted to files whose names are prefixed by
the one of the given directories. If no directories are supplied the
default is
.Pa /tftpboot .
To give out access to the whole filesystem, should this be desired for
some reason, supply 
.Pa / 
as an argument.
.Pp
Unfortunately, on multi-homed systems, it is impossible for
.Nm tftpd
to determine the address on which a packet was received. As a result,
.Nm tftpd
uses two different mechanisms to guess the best source address to use
for replies. If the socket that
.Xr inetd 8
passed to
.Nm tftpd
is bound to a particular address,
.Nm tftpd
uses that address for replies. Otherwise,
.Nm tftpd
uses ``UDP connect'' to let the kernel choose the reply address based
on the destination of the replies and the routing tables. This means
that most setups will work transparently, while in cases where the
reply address must be fixed, the virtual hosting feature of
.Xr inetd 8
can be used to ensure that replies go out from the correct address.
These considerations are important, because most tftp clients will
reject reply packets that appear to come from an unexpected address.
.Pp
The options are:
.Bl -tag -width Ds
.It Fl n
Suppresses negative acknowledgement of requests for nonexistent relative
filenames.
.It Fl s
All absolute filenames are treated as if they were preceded by the first
directory argument, or
.Pa /tftpboot
if there is none.
.El
.Sh SEE ALSO
.Xr tftp 1 ,
.Xr inetd 8
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .