tftpd.tproj/tftpd.8

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  32 .\"     @(#)tftpd.8     8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/libexec/tftpd/tftpd.8,v 1.15 2001/07/15 07:53:42 dd Exp $
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  35 .Dd September 14, 2000
  36 .Dt TFTPD 8
  37 .Os
  38 .Sh NAME
  39 .Nm tftpd
  40 .Nd Internet Trivial File Transfer Protocol server
  41 .Sh SYNOPSIS
  42 .Nm /usr/libexec/tftpd
  43 .Op Fl cCln
  44 .Op Fl s Ar directory
  45 .Op Fl u Ar user
  46 .Op Ar directory ...
  47 .Sh DESCRIPTION
  48 .Nm Tftpd
  49 is a server which supports the
  50 Internet Trivial File Transfer
  51 Protocol
  52 .Pq Tn RFC 1350 .
  53 The
  54 .Tn TFTP
  55 server operates
  56 at the port indicated in the
  57 .Ql tftp
  58 service description;
  59 see
  60 .Xr services 5 .
  61 The server is normally started by
  62 .Xr inetd 8 .
  63 .Pp
  64 The use of
  65 .Xr tftp 1
  66 does not require an account or password on the remote system.
  67 Due to the lack of authentication information,
  68 .Nm
  69 will allow only publicly readable files to be
  70 accessed.
  71 Files containing the string ``/\|\fB.\|.\fP\|/'' or starting with
  72 ``\|\fB.\|.\fP\|/'' are not allowed.
  73 Files may be written only if they already exist and are publicly writable.
  74 Note that this extends the concept of
  75 .Dq public
  76 to include
  77 all users on all hosts that can be reached through the network;
  78 this may not be appropriate on all systems, and its implications
  79 should be considered before enabling tftp service.
  80 The server should have the user ID with the lowest possible privilege.
  81 .Pp
  82 Access to files may be restricted by invoking
  83 .Nm
  84 with a list of directories by including up to 20 pathnames
  85 as server program arguments in
  86 .Pa /etc/inetd.conf .
  87 In this case access is restricted to files whose
  88 names are prefixed by the one of the given directories.
  89 The given directories are also treated as a search path for
  90 relative filename requests.
  91 .Pp
  92 The
  93 .Fl s
  94 option provides additional security by changing
  95 .Nm Ns No 's
  96 root directory, thereby prohibiting accesses outside of the specified
  97 .Ar directory .
  98 Because
  99 .Xr chroot 2
 100 requires super-user privileges,
 101 .Nm
 102 must be run as root.
 103 However, after performing the
 104 .Fn chroot ,
 105 .Nm
 106 will set its user id to that of the specified
 107 .Ar user ,
 108 or
 109 .Dq nobody
 110 if no
 111 .Fl u
 112 option is specified.
 113 .Pp
 114 The options are:
 115 .Bl -tag -width Ds
 116 .It Fl c
 117 Changes the default root directory of a connecting host via chroot based on the
 118 connecting IP address.
 119 This prevents multiple clients from writing to the same file at the same time.
 120 If the directory does not exist, the client connection is refused.
 121 The
 122 .Fl s
 123 option is required for
 124 .Fl c
 125 and the specified
 126 .Ar directory
 127 is used as a base.
 128 .It Fl C
 129 Operates the same as
 130 .Fl c
 131 except it falls back to
 132 .Fl s Ns No 's
 133 .Ar directory
 134 if a directory does not exist for the client's IP.
 135 .It Fl l
 136 Log all requests using
 137 .Xr syslog 3
 138 with the facility of
 139 .Dv LOG_FTP .
 140 Note: Logging of
 141 .Dv LOG_FTP
 142 messages
 143 must also be enabled in the syslog configuration file,
 144 .Xr syslog.conf 5 .
 145 .It Fl n
 146 Suppress negative acknowledgement of requests for nonexistent
 147 relative filenames.
 148 .It Fl s Ar directory
 149 Cause
 150 .Nm
 151 to change its root directory to
 152 .Pa directory .
 153 After changing roots but before accepting commands,
 154 .Nm
 155 will switch credentials to an unprivileged user.
 156 .It Fl u Ar user
 157 Switch credentials to
 158 .Ar user
 159 (default
 160 .Dq nobody )
 161 when the
 162 .Fl s
 163 option is used.
 164 The user must be specified by name, not a numeric UID.
 165 .El
 166 .Sh SEE ALSO
 167 .Xr tftp 1 ,
 168 .Xr chroot 2 ,
 169 .Xr inetd 8 ,
 170 .Xr syslogd 8
 171 .Rs
 172 .%A K. R. Sollins
 173 .%T The TFTP Protocol (Revision 2)
 174 .%D July 1992
 175 .%O RFC 1350, STD 33
 176 .Re
 177 .Sh HISTORY
 178 The
 179 .Nm
 180 command appeared in
 181 .Bx 4.2 ;
 182 the
 183 .Fl s
 184 option was introduced in
 185 .Fx 2.2 ,
 186 the
 187 .Fl u
 188 option was introduced in
 189 .Fx 4.2 ,
 190 and the
 191 .Fl c
 192 option was introduced in
 193 .Fx 4.3 .
 194 .Sh BUGS
 195 Files larger than 33488896 octets (65535 blocks) cannot be transferred
 196 without client and server supporting blocksize negotiation (RFC1783).
 197 .Pp
 198 Many tftp clients will not transfer files over 16744448 octets (32767 blocks).