1TFTPD(8) System Manager's Manual TFTPD(8)
2
6 tftpd - IPv4 Trivial File Transfer Protocol server
7
9 in.tftpd [options...] directory...
10
12 tftpd is a server for the Trivial File Transfer Protocol. The TFTP
13 protocol is extensively used to support remote booting of diskless
14 devices. The server is normally started by inetd, but can also run
15 standalone.
16
18 --ipv4, -4
19 Connect with IPv4 only, even if IPv6 support was compiled in.
20 --ipv6, -6
22 Connect with IPv6 only, if compiled in.
23 -l, --listen
25 Run the server in standalone (listen) mode, rather than run from
26 inetd. In listen mode, the --timeout option is ignored, and the
27 --address option can be used to specify a specific local address
28 or port to listen to.
29 --foreground, -L
31 Similar to --listen but do not detach from the foreground
32 process. Implies --listen.
33 --address [address][:port], -a [address][:port]
35 Specify a specific address and port to listen to when called
36 with the --listen or --foreground option. The default is to
37 listen to the tftp port specified in /etc/services on all local
38 addresses.
39 Please note: Numeric IPv6 adresses must be enclosed in square
41 brackets to avoid ambiguity with the optional port information.
42 --create, -c
44 Allow new files to be created. By default, tftpd will only
45 allow upload of files that already exist. Files are created
46 with default permissions allowing anyone to read or write them,
47 unless the --permissive or --umask options are specified.
48 --secure, -s
50 Change root directory on startup. This means the remote host
51 does not need to pass along the directory as part of the trans‐
52 fer, and may add security. When --secure is specified, exactly
53 one directory should be specified on the command line. The use
54 of this option is recommended for security as well as compati‐
55 bility with some boot ROMs which cannot be easily made to
56 include a directory name in its request.
57 --user username, -u username
59 Specify the username which tftpd will run as; the default is
60 "nobody". The user ID, group ID, and (if possible on the plat‐
61 form) the supplementary group IDs will be set to the ones speci‐
62 fied in the system permission database for this username.
63 --umask umask, -U umask
65 Sets the umask for newly created files to the specified value.
66 The default is zero (anyone can read or write) if the --permis‐
67 sive option is not specified, or inherited from the invoking
68 process if --permissive is specified.
69 --permissive, -p
71 Perform no additional permissions checks above the normal sys‐
72 tem-provided access controls for the user specified via the
73 --user option.
74 --timeout timeout, -t timeout
76 When run from inetd this specifies how long, in seconds, to wait
77 for a second connection before terminating the server. inetd
78 will then respawn the server when another request comes in. The
79 default is 900 (15 minutes.)
80 --retransmit timeout, -T timeout
82 Determine the default timeout, in microseconds, before the first
83 packet is retransmitted. This can be modified by the client if
84 the timeout or utimeout option is negotiated. The default is
85 1000000 (1 second.)
86 --mapfile remap-file, -m remap-file
88 Specify the use of filename remapping. The remap-file is a file
89 containing the remapping rules. See the section on filename
90 remapping below. This option may not be compiled in, see the
91 output of in.tftpd -V to verify whether or not it is available.
92 --verbose, -v
94 Increase the logging verbosity of tftpd. This flag can be spec‐
95 ified multiple times for even higher verbosity.
96 --verbosity value
98 Set the verbosity value to value.
99 --refuse tftp-option, -r tftp-option
101 Indicate that a specific RFC 2347 TFTP option should never be
102 accepted.
103 --blocksize max-block-size, -B max-block-size
105 Specifies the maximum permitted block size. The permitted range
106 for this parameter is from 512 to 65464. Some embedded clients
107 request large block sizes and yet do not handle fragmented pack‐
108 ets correctly; for these clients, it is recommended to set this
109 value to the smallest MTU on your network minus 32 bytes (20
110 bytes for IP, 8 for UDP, and 4 for TFTP; less if you use IP
111 options on your network.) For example, on a standard Ethernet
112 (MTU 1500) a value of 1468 is reasonable.
113 --port-range port:port, -R port:port
115 Force the server port number (the Transaction ID) to be in the
116 specified range of port numbers.
117 --version, -V
119 Print the version number and configuration to standard output,
120 then exit gracefully.
121
123 This version of tftpd supports RFC 2347 option negotation. Currently
124 implemented options are:
125 blksize (RFC 2348)
127 Set the transfer block size to anything less than or equal to
128 the specified option. This version of tftpd can support any
129 block size up to the theoretical maximum of 65464 bytes.
130 blksize2 (nonstandard)
132 Set the transfer block size to anything less than or equal to
133 the specified option, but restrict the possible responses to
134 powers of 2. The maximum is 32768 bytes (the largest power of 2
135 less than or equal to 65464.)
136 tsize (RFC 2349)
138 Report the size of the file that is about to be transferred.
139 This version of tftpd only supports the tsize option for binary
140 (octet) mode transfers.
141 timeout (RFC 2349)
143 Set the time before the server retransmits a packet, in seconds.
144 utimeout (nonstandard)
146 Set the time before the server retransmits a packet, in
147 microseconds.
148 The --refuse option can be used to disable specific options; this may
150 be necessary to work around bugs in specific TFTP client implementa‐
151 tions. For example, some TFTP clients have been found to request the
152 blksize option, but crash with an error if they actually get the option
153 accepted by the server.
154
156 The --mapfile option specifies a file which contains filename remapping
157 rules. Each non-comment line (comments begin with hash marks, #) con‐
158 tains an operation, specified below; a regex, a regular expression in
159 the style of egrep; and optionally a replacement pattern. The opera‐
160 tion indicated by operation is performed if the regex matches all or
161 part of the filename. Rules are processed from the top down, and by
162 default, all rules are processed even if there is a match.
163 The operation can be any combination of the following letters:
165 r Replace the substring matched by regex by the replacement pat‐
167 tern. The replacement pattern may contain escape sequences; see
168 below.
169 g Repeat this rule until it no longer matches. This is always
171 used with r.
172 i Match the regex case-insensitively. By default it is case sen‐
174 sitive.
175 e If this rule matches, end rule processing after executing the
177 rule.
178 s If this rule matches, start rule processing over from the very
180 first rule after executing this rule.
181 a If this rule matches, refuse the request and send an access
183 denied error to the client.
184 G This rule applies to GET (RRQ) requests only.
186 P This rule applies to PUT (WRQ) requests only.
188 ~ Inverse the sense of this rule, i.e. execute the operation only
190 if the regex doesn't match. Cannot used together with r.
191 The following escape sequences are recognized as part of the replace‐
193 ment pattern:
194 \0 The entire string matched by the regex.
196 \1 to \9
198 The strings matched by each of the first nine parenthesized sub‐
199 expressions, \( ... \), of the regex pattern.
200 \i The IP address of the requesting host, in dotted-quad notation
202 (e.g. 192.0.2.169).
203 \x The IP address of the requesting host, in hexadecimal notation
205 (e.g. C00002A9).
206 \\ Literal backslash.
208 \whitespace
210 Literal whitespace.
211 \# Literal hash mark.
213 \U Turns all subsequent letters to upper case.
215 \L Turns all subsequent letters to lower case.
217 \E Cancels the effect of \U or \L.
219 If the mapping file is changed, you need to send SIGHUP to any out‐
221 standing tftpd process.
222
224 The use of TFTP services does not require an account or password on the
225 server system. Due to the lack of authentication information, tftpd
226 will allow only publicly readable files (o+r) to be accessed, unless
227 the --permissive option is specified. Files may be written only if
228 they already exist and are publicly writable, unless the --create
229 option is specified. Note that this extends the concept of ``public''
230 to include all users on all hosts that can be reached through the net‐
231 work; this may not be appropriate on all systems, and its implications
232 should be considered before enabling TFTP service. Typically, some
233 kind of firewall or packet-filter solution should be employed. If
234 appropriately compiled (see the output of in.tftpd --version) tftpd
235 will query the hosts_access(5) database for access control information.
236 This may be slow; sites requiring maximum performance may want to com‐
237 pile without this option and rely on firewalling or kernel-based packet
238 filters instead.
239 The server should be set to run as the user with the lowest possible
241 privilege; please see the --user flag. It is probably a good idea to
242 set up a specific user account for tftpd, rather than letting it run as
243 "nobody", to guard against privilege leaks between applications.
244 Access to files can, and should, be restricted by invoking tftpd with a
246 list of directories by including pathnames as server program arguments
247 on the command line. In this case access is restricted to files whole
248 names are prefixed by one of the given directories. If possible, it is
249 recommended that the --secure flag is used to set up a chroot() envi‐
250 ronment for the server to run in once a connection has been set up.
251 Finally, the filename remapping (--mapfile flag) support can be used to
253 provide a limited amount of additional access control.
254
256 RFC 1123, Requirements for Internet Hosts - Application and Support.
257 RFC 1350, The TFTP Protocol (revision 2).
258 RFC 2347, TFTP Option Extension.
259 RFC 2348, TFTP Blocksize Option.
260 RFC 2349, TFTP Timeout Interval and Transfer Size Options.
261
263 This version of tftpd is maintained by H. Peter Anvin <hpa@zytor.com>.
264 It was derived from, but has substantially diverged from, an OpenBSD
265 source base, with added patches by Markus Gutschke and Gero Kulhman.
266
268 tftp(1), egrep(1), umask(2), hosts_access(5), regex(7), inetd(8).
269tftp-hpa 0.49 30 July 2008 TFTPD(8)