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    23 .TH "ntp.conf" "5" "" "" "File Formats"

    24 .SH NAME

    25 ntp.conf \- Configuration file for the NTP Daemon.

    26 .SH DESCRIPTION

    27 .LP

    28 The \fB\&ntp.conf\fR file contains the directives used by the \fBntpd\fR to

    29 configure itself. 

    30 .SS "Configuration Commands"

    31 .sp 1.5

    32 .ne 2

    33 .mk

    34 .na

    35 \fBserver \fIaddress\fP \fR[options ...]\fP\fR

    36 .br

    37 \fBpeer \fIaddress\fP \fR[options ...]\fP\fR

    38 .br

    39 \fBbroadcast \fIaddress\fP \fR[options ...]\fP\fR

    40 .br

    41 \fBmanycastclient \fIaddress\fP \fR[options ...]\fP\fR

    42 .br

    43 \fR\fBpool \fIaddress\fP \fR[options ...]\fP\fR

    44 .ad

    45 .sp .25

    46 .RS 4n

    47 These commands specify the time server name or address to be used and the mode in which to operate. The \fIaddress\fP can be either a DNS name or a IPv4 or IPv6 address in standard notation. In general, multiple commands of each type can be used for different server and peer addresses or multicast groups.

    48 .RE

    49 .sp .3

    50 .ne 2

    51 .mk

    52 .na

    53 \fBserver\fR

    54 .ad

    55 .sp .25

    56 .RS 4n

    57 For type s and r addresses (only), this command mobilizes a persistent client mode association with the specified remote server or local reference clock. If the \fBpreempt\fR flag is specified, a preemptable client mode association is mobilized instead.

    58 .RE

    59 .sp .3

    60 .ne 2

    61 .mk

    62 .na

    63 \fBpeer\fR

    64 .ad

    65 .sp .25

    66 .RS 4n

    67 For type s addresses (only), this command mobilizes a persistent symmetric-active mode association with the specified remote peer.

    68 .RE

    69 .sp .3

    70 .ne 2

    71 .mk

    72 .na

    73 \fBbroadcast\fR

    74 .ad

    75 .sp .25

    76 .RS 4n

    77 For type b and m ddresses (only), this command mobilizes a persistent broadcast or multicast server mode association. Note that type b messages go only to the interface specified, but type m messages go to all interfaces.

    78 .RE

    79 .sp .3

    80 .ne 2

    81 .mk

    82 .na

    83 \fBmanycastclient\fR

    84 .ad

    85 .sp .25

    86 .RS 4n

    87 For type m addresses (only), this command mobilizes a manycast client mode association for the multicast group address specified. In this mode the address must match the address specified on the \fBmanycastserver\fR command of one or more designated manycast servers.

    88 .RE

    89 .sp .3

    90 .ne 2

    91 .mk

    92 .na

    93 \fBpool\fR

    94 .ad

    95 .sp .25

    96 .RS 4n

    97 For type s messages (only) this command mobilizes a client mode association for servers implementing the pool automatic server discovery scheme described on the Association Management page at file:///usr/share/doc/ntp/assoc.html. The address is a DNS name in the form \fB\fIarea\fP.pool.ntp.org\fR, where \fB\fIarea\fP\fR is a qualifier designating the server geographic area such as \fBus\fR or \fBeurope\fR.

    98 .SS "Command Options"

    99 Each of the above configuation commands takes zero or more options from the list below:

   100 .sp .3

   101 .ne 2

   102 .mk

   103 .na

   104 \fBautokey\fR

   105 .ad

   106 .sp .25

   107 .RS 4n

   108 Send and receive packets authenticated by the autokey scheme described in the Authentication Options page at file:///usr/share/doc/ntp/authopt.html. This option is valid only with \fBserver\fR and \fBpeer\fR commands and type s addresses. It is incompatible with the \fBkey\fR option.

   109 .RE

   110 .sp .3

   111 .ne 2

   112 .mk

   113 .na

   114 \fBburst\fR

   115 .ad

   116 .sp .25

   117 .RS 4n

   118 When the server is reachable, send a burst of six packets instead of the usual one. The packet spacing is normally 2 s; however, the spacing between the first and second packets can be changed with the fBcalldelay\fR command to allow additional time for a modem or ISDN call to complete. This option is valid only with only the \fBserver\fR command and type s addressesa. It is a recommended option when the \fBmaxpoll\fR option is greater than 10 (1024 s).

   119 .RE

   120 .sp .3

   121 .ne 2

   122 .mk

   123 .na

   124 \fBiburst\fR

   125 .ad

   126 .sp .25

   127 .RS 4n

   128 When the server is unreachable, send a burst of eight packets instead of the usual one. The packet spacing is normally 2 s; however, the spacing between the first and second packets can be changed with the \fBcalldelay\fR command to allow additional time for a modem or ISDN call to complete. This option is valid only with the \fBserver\fR command and type s addresses. It is a recommended option with this command.

   129 .RE

   130 .sp .3

   131 .ne 2

   132 .mk

   133 .na

   134 \fBkey\fR \fIkey\fP\fR

   135 .ad

   136 .sp .25

   137 .RS 4n

   138 Send and receive packets authenticated by the symmetric key scheme described in the Authentication Options page at file:///usr/share/doc/ntp/authopt.html. This option is valid only with \fBserver\fR and \fBpeer\fR commands and type s addresses. The \fIkey\fP specifies the key identifier with values from 1 to 65534, inclusive. This option is incompatible with the \fBautokey\fR option.

   139 .RE

   140 .sp .3

   141 .ne 2

   142 .mk

   143 .na

   144 \fBminpoll \fIminpoll

   145 .br

   146 \fP\fR\fBmaxpoll \fImaxpoll\fP\fR

   147 .ad

   148 .sp .25

   149 .RS 4n

   150 These options specify the minimum and maximum poll intervals for NTP messages, in seconds as a power of two. The maximum poll interval defaults to 10 (1024 s), but can be increased by the \fBmaxpoll\fR option to an upper limit of 17 (36 h). The minimum poll interval defaults to 6 (64 s), but can be decreased by the \fBminpoll\fR option to a lower limit of 4 (16 s). These option are valid only with the \fBserver\fR and \fBpeer\fR commands and type s addresses.

   151 .RE

   152 .sp .3

   153 .ne 2

   154 .mk

   155 .na

   156 \fBmode \fIoption\fP\fR

   157 .ad

   158 .sp .25

   159 .RS 4n

   160 Pass the \fB\fIoption\fP\fR to a reference clock driver, where \fB\fIoption\fP\fR is an integer in the range from 0 to 255, inclusive. This option is valid only with the \fBserver\fR command and type r addresses.

   161 .RE

   162 .sp .3

   163 .ne 2

   164 .mk

   165 .na

   166 \fBnoselect\fR

   167 .ad

   168 .sp .25

   169 .RS 4n

   170 Marks the server or peer to be ignored by the selection algorithm but visible to the monitoring program. This option is ignored with the \fBbroadcast\fR command.

   171 .RE

   172 .sp .3

   173 .ne 2

   174 .mk

   175 .na

   176 \fBpreempt\fR

   177 .ad

   178 .sp .25

   179 .RS 4n

   180 Specifies the association as preemptable rather than the default persistent. This option is ignored with the  \fBbroadcast\fR command and is most useful with the \fBmanycastclient\fR and \fBpool\fR commands.

   181 .RE

   182 .sp .3

   183 .ne 2

   184 .mk

   185 .na

   186 \fBprefer\fR

   187 .ad

   188 .sp .25

   189 .RS 4n

   190 Mark the server as preferred. All other things being equal, this host will be chosen for synchronization among a set of correctly operating hosts. See the Mitigation Rules page at file:///usr/share/doc/ntp/prefer.html for further information. This option is valid only with the \fBserver\fR and \fBpeer\fR commands.

   191 .RE

   192 .sp .3

   193 .ne 2

   194 .mk

   195 .na

   196 \fBtrue\fR

   197 .ad

   198 .sp .25

   199 .RS 4n

   200 Mark the association to assume truechimer status; that is, always survive the selection and clustering algorithms. This option can be used with any association, but is most useful for reference clocks with large jitter on the serial port and precision pulse-per-second (PPS) signals. Caution: this option defeats the algorithms designed to cast out falsetickers and can allow these sources to set the system clock. This option is valid only with the \fBserver\fR and \fBpeer\fR commands.

   201 .RE

   202 .sp .3

   203 .ne 2

   204 .mk

   205 .na

   206 \fBttl \fIttl\fP\fR

   207 .ad

   208 .sp .25

   209 .RS 4n

   210 This option specifies the time-to-live \fIttl\fP for the \fBbroadcast\fR commmand and the maximum \fIttl\fP for the expanding ring search used by the \fBmanycastclient\fR command. Selection of the proper value, which defaults to 127, is something of a black art and should be coordinated with the network administrator.

   211 .RE

   212 .sp .3

   213 .ne 2

   214 .mk

   215 .na

   216 \fBversion \fIversion\fP\fR

   217 .ad

   218 .sp .25

   219 .RS 4n

   220 Specifies the version number to be used for outgoing NTP packets. Versions 1-4 are the choices, with version 4 the default.

   221 .RE

   222 .SS "Auxilliary Commands"

   223 .sp .3

   224 .ne 2

   225 .mk

   226 .na

   227 \fBbroadcastclient [novolley]\fR

   228 .ad

   229 .sp .25

   230 .RS 4n

   231 Enable reception of broadcast server messages to any local interface (type b address). Ordinarily, upon receiving a message for the first time, the broadcast client measures the nominal server propagation delay using a brief client/server exchange, after which it continues in listen-only mode. If the \fBnovolley\fR keyword is present, the exchange is not used and the value specified in the \fBbroadcastdelay\fR command is used or, if the \fBbroadcastdelay\fR command is not used, the default 4.0 ms. Note that, in order to avoid accidental or malicious disruption in this mode, both the server and client should operate using symmetric key or public key authentication as described in the Authentication Options page at file:///usr/share/doc/ntp/authopt.html. Note that the \fBnovolley\fR keyword is incompatible with public key authentication.

   232 .RE

   233 .sp .3

   234 .ne 2

   235 .mk

   236 .na

   237 \fBmanycastserver \fIaddress\fP [...]\fR

   238 .ad

   239 .sp .25

   240 .RS 4n

   241 Enable reception of manycast client messages (type m)to the multicast group address(es) (type m) specified. At least one address is required. Note that, in order to avoid accidental or malicious disruption, both the server and client should operate using symmetric key or public key authentication as described in the Authentication Options page at file:///usr/share/doc/ntp/authopt.html.

   242 .RE

   243 .sp .3

   244 .ne 2

   245 .mk

   246 .na

   247 \fBmulticastclient \fIaddress\fP [...]\fR

   248 .ad

   249 .sp .25

   250 .RS 4n

   251 Enable reception of multicast server messages to the multicast group address(es) (type m) specified. Upon receiving a message for the first time, the multicast client measures the nominal server propagation delay using a brief client/server exchange with the server, then enters the broadcast client mode, in which it synchronizes to succeeding multicast messages. Note that, in order to avoid accidental or malicious disruption in this mode, both the server and client should operate using symmetric key or public key authentication as described in the Authentication Options page at file:///usr/share/doc/ntp/authopt.html.

   252 .RE

   253 .SS "Reference Clock Commands"

   254 .sp .3

   255 .ne 2

   256 .mk

   257 .na

   258 \fBserver 127.127.\fIt.u\fP [prefer] [mode \fIint\fP] [minpoll \fIint\fP] [maxpoll \fIint\fP]\fR

   259 .ad

   260 .sp .25

   261 .RS 4n

   262 This command can be used to configure reference clocks in special ways. The options are interpreted as follows:

   263 .RE

   264 .sp .3

   265 .ne 2

   266 .mk

   267 .na

   268 \fBprefer\fR

   269 .ad

   270 .sp .25

   271 .RS 4n

   272 Marks the reference clock as preferred. All other things being equal, this host will be chosen for synchronization among a set of correctly operating hosts. See the Mitigation Rules page at file:///usr/share/doc/ntp/prefer.html for further information.

   273 .RE

   274 .sp .3

   275 .ne 2

   276 .mk

   277 .na

   278 \fBmode \fIint\fP\fR

   279 .ad

   280 .sp .25

   281 .RS 4n

   282 Specifies a mode number which is interpreted in a device-specific fashion. For instance, it selects a dialing protocol in the ACTS driver and a device subtype in the \fBparse\fR drivers.

   283 .RE

   284 .sp .3

   285 .ne 2

   286 .mk

   287 .na

   288 \fBminpoll \fIint\fP\fR

   289 .RE

   290 .sp .3

   291 .ne 2

   292 .mk

   293 .na

   294 \fBmaxpoll \fIint\fP\fR

   295 .ad

   296 .sp .25

   297 .RS 4n

   298 These options specify the minimum and maximum polling interval for reference clock messages in seconds, interpreted as dual logarithms (2 ^ x). For most directly connected reference clocks, both \fBminpoll\fR and \fBmaxpoll\fR default to 6 (2^16 = 64 s). For modem reference clocks, \fBminpoll\fR defaults to 10 (2^10 = 1024 s = 17.1 m) and \fBmaxpoll\fR defaults to 14 (2^14 = 16384 s = 4.25 h). The allowable range is 4 (16 s) to 17 (36.4 h) inclusive.

   299 .RE

   300 .sp .3

   301 .ne 2

   302 .mk

   303 .na

   304 \fBfudge 127.127.\fIt.u\fP [time1 \fIsec\fP] [time2 \fIsec\fP] [stratum \fIint\fP] [refid \fIstring\fP] [mode \fIint\fP] [flag1 0|1] [flag2 0|1] [flag3 0|1] [flag4 0|1]\fR

   305 .ad

   306 .sp .25

   307 .RS 4n

   308 This command can be used to configure reference clocks in special ways. It must immediately follow the \fBserver\fR command which configures the driver. Note that the same capability is possible at run time using the \fBntpdc\fR program. The options are interpreted as follows:

   309 .RE

   310 .sp .3

   311 .ne 2

   312 .mk

   313 .na

   314 \fBtime1 \fIsec\fP\fR

   315 .ad

   316 .sp .25

   317 .RS 4n

   318 Specifies a constant to be added to the time offset produced by the driver, a fixed-point decimal number in seconds. This is used as a calibration constant to adjust the nominal time offset of a particular clock to agree with an external standard, such as a precision PPS signal. It also provides a way to correct a systematic error or bias due to serial port or operating system latencies, different cable lengths or receiver internal delay. The specified offset is in addition to the propagation delay provided by other means, such as internal DIPswitches. Where a calibration for an individual system and driver is available, an approximate correction is noted in the driver documentation pages.

   319 .LP

   320 Note: in order to facilitate calibration when more than one radio clock or PPS signal is supported, a special calibration feature is available. It takes the form of an argument to the \fBenable\fR command and operates as described in the Reference Clock Drivers page at file:///usr/share/doc/ntp/refclock.html.

   321 .RE

   322 .sp .3

   323 .ne 2

   324 .mk

   325 .na

   326 \fBtime2 \fIsecs\fP\fR

   327 .ad

   328 .sp .25

   329 .RS 4n

   330 Specifies a fixed-point decimal number in seconds, which is interpreted in a driver-dependent way. See the descriptions of specific drivers in the Reference Clock Drivers page at file:///usr/share/doc/ntp/refclock.html.

   331 .RE

   332 .sp .3

   333 .ne 2

   334 .mk

   335 .na

   336 \fBstratum \fIint\fP\fR

   337 .ad

   338 .sp .25

   339 .RS 4n

   340 Specifies the stratum number assigned to the driver, an integer between 0 and 15. This number overrides the default stratum number ordinarily assigned by the driver itself, usually zero.

   341 .RE

   342 .sp .3

   343 .ne 2

   344 .mk

   345 .na

   346 \fBrefid \fIstring\fP\fR

   347 .ad

   348 .sp .25

   349 .RS 4n

   350 Specifies an ASCII string of from one to four characters which defines the reference identifier used by the driver. This string overrides the default identifier ordinarily assigned by the driver itself.

   351 .RE

   352 .sp .3

   353 .ne 2

   354 .mk

   355 .na

   356 \fBmode \fIint\fP\fR

   357 .ad

   358 .sp .25

   359 .RS 4n

   360 Specifies a mode number which is interpreted in a device-specific fashion. For instance, it selects a dialing protocol in the ACTS driver and a device subtype in the \fBparse\fR drivers.

   361 .RE

   362 .sp .3

   363 .ne 2

   364 .mk

   365 .na

   366 \fBflag1 flag2 flag3 flag4\fR

   367 .ad

   368 .sp .25

   369 .RS 4n

   370 These four flags are used for customizing the clock driver. The interpretation of these values, and whether they are used at all, is a function of the particular clock driver. However, by convention \fBflag4\fR is used to enable recording monitoring data to the \fBclockstats\fR file configured with the \fBfilegen\fR command. 

   371 .RE

   372 .SS "Authentication Commands"

   373 .sp .3

   374 .ne 2

   375 .mk

   376 .na

   377 \fBautokey [\fIlogsec\fP]\fR

   378 .ad

   379 .sp .25

   380 .RS 4n

   381 Specifies the interval between regenerations of the session key list used with the Autokey protocol. Note that the size of the key list for each association depends on this interval and the current poll interval. The default value is 12 (4096 s or about 1.1 hours). For poll intervals above the specified interval, a session key list with a single entry will be regenerated for every message sent.

   382 .RE

   383 .sp .3

   384 .ne 2

   385 .mk

   386 .na

   387 \fBcontrolkey \fIkey\fP\fR

   388 .ad

   389 .sp .25

   390 .RS 4n

   391 Specifies the key identifier to use with the \fBntpq\fR utility, which uses the standard protocol defined in RFC-1305. The \fB\fIkey\fP\fR argument is the key identifier for a trusted key, where the value can be in the range 1 to 65,534, inclusive.

   392 .RE

   393 .sp .3

   394 .ne 2

   395 .mk

   396 .na

   397 \fBcrypto [randfile \fIfile\fP] [host \fIname\fP] [ident \fIname\fP] [pw \fIpassword\fP]\fR

   398 .ad

   399 .sp .25

   400 .RS 4n

   401 This command requires the OpenSSL library. It activates public key cryptography and loads the required public/private encryption and sign kyes and public certificat. If one or more files are left unspecified, the default names are used as described below. Unless the complete path and name of the file are specified, the location of a file is relative to the keys directory specified in the \fBkeysdir\fR command or default \fB/etc/inet\fR. Following are the subcommands.

   402 .RE

   403 .sp .3

   404 .ne 2

   405 .mk

   406 .na

   407 \fBhost \fIname\fP\fR

   408 .ad

   409 .sp .25

   410 .RS 4n

   411 Specifies the host name used in the host key link \fBntpkey_host_\fIname\fP\fR, sign key link \fBntpkey_sign_\fIname\fP\fR and certificate link \fBntpkey_cert_\fIname\fP\fR. The \fBntp-keygen\fR program automatically installs these links to the most recently generated files.

   412 .RE

   413 .sp .3

   414 .ne 2

   415 .mk

   416 .na

   417 \fBident \fIname\fP\fR

   418 .ad

   419 .sp .25

   420 .RS 4n

   421 Specifies the group name used in the identity key link \fBntpkey_\fIkey\fP_\fIname\fP\fR, where \fB\fIkey\fP\fR identifies the key type described on the \fBntp-keygen\fR page. The \fBntp-keygen\fR program automatically installs these links to the most recently generated files.

   422 .RE

   423 .sp .3

   424 .ne 2

   425 .mk

   426 .na

   427 \fBpw \fIpassword\fP\fR

   428 .ad

   429 .sp .25

   430 .RS 4n

   431 Specifies the password to decrypt files previously encrypted by the \fBntp-keygen\fR program.

   432 .RE

   433 .sp .3

   434 .ne 2

   435 .mk

   436 .na

   437 \fBrandfile \fIfile\fP\fR

   438 .ad

   439 .sp .25

   440 .RS 4n

   441 Specifies the location of the random seed file used by the OpenSSL library. The defaults are described on the \fBntp-keygen(8)\fR man page.

   442 .RE

   443 .sp .3

   444 .ne 2

   445 .mk

   446 .na

   447 \fBkeys \fIkeyfile\fP\fR

   448 .ad

   449 .sp .25

   450 .RS 4n

   451 Specifies the complete path to the MD5 key file containing the keys and key identifiers used by \fBntpd\fR, \fBntpq\fR and \fBntpdc\fR when operating with symmetric key cryptography. This is the same operation as the \fB-k \fRcommand line option.

   452 .RE

   453 .sp .3

   454 .ne 2

   455 .mk

   456 .na

   457 \fBkeysdir \fIpath\fP\fR

   458 .ad

   459 .sp .25

   460 .RS 4n

   461 This command specifies the default directory path for cryptographic keys, parameters and certificates. The default is \fB/etc/inet/\fR.

   462 .RE

   463 .sp .3

   464 .ne 2

   465 .mk

   466 .na

   467 \fBrequestkey \fIkey\fP\fR

   468 .ad

   469 .sp .25

   470 .RS 4n

   471 Specifies the key identifier to use with the \fBntpdc\fR utility program, which uses a proprietary protocol specific to this implementation of \fBntpd\fR. The \fB\fIkey\fP\fR argument is a key identifier for the trusted key, where the value can be in the range 1 to 65,534, inclusive.

   472 .RE

   473 .sp .3

   474 .ne 2

   475 .mk

   476 .na

   477 \fBrevoke [\fIlogsec\fP]\fR

   478 .ad

   479 .sp .25

   480 .RS 4n

   481 Specifies the interval between re-randomization of certain cryptographic values used by the Autokey scheme, as a power of 2 in seconds. These values need to be updated frequently in order to deflect brute-force attacks on the algorithms; however, updating some values is a relatively expensive operation. The default interval is 16 (65,536 s or about 18 hours). For poll intervals above the specified interval, the values will be updated for every message sent.

   482 .RE

   483 .sp .3

   484 .ne 2

   485 .mk

   486 .na

   487 \fBtrustedkey \fIkey\fP [...]\fR

   488 .ad

   489 .sp .25

   490 .RS 4n

   491 Specifies the key identifiers which are trusted for the purposes of authenticating peers with symmetric key cryptography, as well as keys used by the \fBntpq\fR and \fBntpdc\fR programs. The authentication procedures require that both the local and remote servers share the same key and key identifier for this purpose, although different keys can be used with different servers. The \fB\fIkey\fP\fR arguments are 32-bit unsigned integers with values from 1 to 65,534.

   492 .RE

   493 .SS "Access Control Commands"

   494 .sp .3

   495 .ne 2

   496 .mk

   497 .na

   498 \fBdiscard [ average \fIavg\fP ][ minimum \fImin\fP ] [ monitor \fIprob\fP ]\fR

   499 .ad

   500 .sp .25

   501 .RS 4n

   502 Set the parameters of the \fBlimited\fR facility which protects the server from client abuse. The \fBaverage\fR subcommand specifies the minimum average packet spacing, while the \fBminimum\fR subcommand specifies the minimum packet spacing. Packets that violate these minima are discarded and a kiss-o'-death packet returned if enabled. The default minimum average and minimum are 5 and 2, respectively. The monitor subcommand specifies the probability of discard for packets that overflow the rate-control window.

   503 .RE

   504 .sp .3

   505 .ne 2

   506 .mk

   507 .na

   508 \fBrestrict \fIaddress\fP [mask \fImask\fP] [\fIflag\fP][...]\fR

   509 .ad

   510 .sp .25

   511 .RS 4n

   512 The \fIaddress\fP argument expressed in dotted-quad form is the address of a host or network. Alternatively, the \fB\fIaddress\fP\fR argument can be a valid host DNS name. The \fImask\fP argument expressed in dotted-quad form defaults to \fB255.255.255.255\fR, meaning that the \fIaddress\fP is treated as the address of an individual host. A default entry (address \fB0.0.0.0\fR, mask \fB0.0.0.0\fR) is always included and is always the first entry in the list. Note that text string \fBdefault\fR, with no mask option, may be used to indicate the default entry.

   513 .LP

   514 In the current implementation, \fIflag\fP always restricts access, i.e., an entry with no flags indicates that free access to the server is to be given. The flags are not orthogonal, in that more restrictive flags will often make less restrictive ones redundant. The flags can generally be classed into two catagories, those which restrict time service and those which restrict informational queries and attempts to do run-time reconfiguration of the server. One or more of the following flags may be specified:

   515 .RE

   516 .sp .3

   517 .ne 2

   518 .mk

   519 .na

   520 \fBignore\fR

   521 .ad

   522 .sp .25

   523 .RS 4n

   524 Deny packets of all kinds, including \fBntpq\fR and \fBntpdc\fR queries.

   525 .RE

   526 .sp .3

   527 .ne 2

   528 .mk

   529 .na

   530 \fBkod\fR

   531 .ad

   532 .sp .25

   533 .RS 4n

   534 If this flag is set when an access violation occurs, a kiss-o'-death (KoD) packet is sent. KoD packets are rate limited to no more than one per second. If another KoD packet occurs within one second after the last one, the packet is dropped

   535 .RE

   536 .sp .3

   537 .ne 2

   538 .mk

   539 .na

   540 \fBlimited\fR

   541 .ad

   542 .sp .25

   543 .RS 4n

   544 Deny service if the packet spacing violates the lower limits specified in the \fBdiscard\fR command. A history of clients is kept using the monitoring capability of \fBntpd\fR. Thus, monitoring is always active as long as there is a restriction entry with the \fBlimited\fR flag.

   545 .RE

   546 .sp .3

   547 .ne 2

   548 .mk

   549 .na

   550 \fBlowpriotrap\fR

   551 .ad

   552 .sp .25

   553 .RS 4n

   554 Declare traps set by matching hosts to be low priority. The number of traps a server can maintain is limited (the current limit is 3). Traps are usually assigned on a first come, first served basis, with later trap requestors being denied service. This flag modifies the assignment algorithm by allowing low priority traps to be overridden by later requests for normal priority traps.

   555 .RE

   556 .sp .3

   557 .ne 2

   558 .mk

   559 .na

   560 \fBnomodify\fR

   561 .ad

   562 .sp .25

   563 .RS 4n

   564 Deny \fBntpq\fR and \fBntpdc\fR queries which attempt to modify the state of the server (i.e., run time reconfiguration). Queries which return information are permitted.

   565 .RE

   566 .sp .3

   567 .ne 2

   568 .mk

   569 .na

   570 \fBnoquery\fR

   571 .ad

   572 .sp .25

   573 .RS 4n

   574 Deny \fBntpq\fR and \fBntpdc\fR queries. Time service is not affected.

   575 .RE

   576 .sp .3

   577 .ne 2

   578 .mk

   579 .na

   580 \fBnopeer\fR

   581 .ad

   582 .sp .25

   583 .RS 4n

   584 Deny packets which would result in mobilizing a new association.  This includes broadcast, symmetric-active and manycast client packets when a configured association does not exist.

   585 .RE

   586 .sp .3

   587 .ne 2

   588 .mk

   589 .na

   590 \fBnoserve\fR

   591 .ad

   592 .sp .25

   593 .RS 4n

   594 Deny all packets except \fBntpq\fR and \fBntpdc\fR queries.

   595 .RE

   596 .sp .3

   597 .ne 2

   598 .mk

   599 .na

   600 \fBnotrap\fR

   601 .ad

   602 .sp .25

   603 .RS 4n

   604 Decline to provide mode 6 control message trap service to matching hosts. The trap service is a subsystem of the \fBntpdq\fR control message protocol which is intended for use by remote event logging programs.

   605 .RE

   606 .sp .3

   607 .ne 2

   608 .mk

   609 .na

   610 \fBnotrust\fR

   611 .ad

   612 .sp .25

   613 .RS 4n

   614 Deny packets unless the packet is cryptographically authenticated.

   615 .RE

   616 .sp .3

   617 .ne 2

   618 .mk

   619 .na

   620 \fBntpport\fR

   621 .ad

   622 .sp .25

   623 .RS 4n

   624 This is actually a match algorithm modifier, rather than a restriction flag. Its presence causes the restriction entry to be matched only if the source port in the packet is the standard NTP UDP port (123). Both \fBntpport\fR and \fBnon-ntpport\fR may be specified. The \fBntpport\fR is considered more specific and is sorted later in the list.

   625 .RE

   626 .sp .3

   627 .ne 2

   628 .mk

   629 .na

   630 \fBversion\fR

   631 .ad

   632 .sp .25

   633 .RS 4n

   634 Deny packets that do not match the current NTP version.

   635 .RE

   636 .SS "Monitoring Commands"

   637 .sp .3

   638 .ne 2

   639 .mk

   640 .na

   641 \fBstatistics \fIname\fP [...]\fR

   642 .ad

   643 .sp .25

   644 .RS 4n

   645 Enables writing of statistics records. Currently, six kinds of \fIname\fPstatistics are supported.

   646 .RE

   647 .sp .3

   648 .ne 2

   649 .mk

   650 .na

   651 \fBclockstats\fR

   652 .ad

   653 .sp .25

   654 .RS 4n

   655 Enables recording of clock driver statistics information. Each update received from a clock driver appends a line of the following form to the file generation set named \fBclockstats\fR:

   656 .LP

   657 \fB49213 525.624 127.127.4.1 93 226 00:08:29.606 D\fR

   658 .LP

   659 The first two fields show the date (Modified Julian Day) and time (seconds and fraction past UTC midnight). The next field shows the clock address in dotted-quad notation, The final field shows the last timecode received from the clock in decoded ASCII format, where meaningful. In some clock drivers a good deal of additional information can be gathered and displayed as well. See information specific to each clock for further details.

   660 .RE

   661 .sp .3

   662 .ne 2

   663 .mk

   664 .na

   665 \fBcryptostats\fR

   666 .ad

   667 .sp .25

   668 .RS 4n

   669 This option requires the OpenSSL cryptographic software library. It enables recording of cryptographic public key protocol information. Each message received by the protocol module appends a line of the following form to the file generation set named \fBcryptostats\fR:

   670 .LP

   671 \fB49213 525.624 127.127.4.1 \fImessage\fP\fR

   672 .LP

   673 The first two fields show the date (Modified Julian Day) and time (seconds and fraction past UTC midnight). The next field shows the peer address in dotted-quad notation, The final \fB\fImessage\fP\fR field includes the message type and certain ancillary information. See the Authentication Options page at file:///usr/share/doc/ntp/authopt.html for further information.

   674 .RE

   675 .sp .3

   676 .ne 2

   677 .mk

   678 .na

   679 \fBloopstats\fR

   680 .ad

   681 .sp .25

   682 .RS 4n

   683 Enables recording of loop filter statistics information. Each update of the local clock outputs a line of the following form to the file generation set named \fBloopstats\fR:

   684 .LP

   685 \fB50935 75440.031 0.000006019 13.778190 0.000351733 0.0133806	6\fR

   686 .LP

   687 The first two fields show the date (Modified Julian Day) and time (seconds and fraction past UTC midnight). The next five fields show time offset (seconds), frequency offset (parts per million - PPM), RMS jitter (seconds), Allan deviation (PPM) and clock discipline time constant.

   688 .RE

   689 .sp .3

   690 .ne 2

   691 .mk

   692 .na

   693 \fBpeerstats\fR

   694 .ad

   695 .sp .25

   696 .RS 4n

   697 Enables recording of peer statistics information. This includes statistics records of all peers of a NTP server and of special signals, where present and configured. Each valid update appends a line of the following form to the current element of a file generation set named \fBpeerstats\fR:

   698 .LP

   699 \fB48773 10847.650 127.127.4.1 9714 -0.001605376 0.000000000 0.001424877 0.000958674\fR

   700 .LP

   701 The first two fields show the date (Modified Julian Day) and time (seconds and fraction past UTC midnight). The next two fields show the peer address in dotted-quad notation and status, respectively. The status field is encoded in hex in the format described in Appendix B of the NTP specification RFC 1305. The final four fields show the offset, delay, dispersion and RMS jitter, all in seconds.

   702 .RE

   703 .sp .3

   704 .ne 2

   705 .mk

   706 .na

   707 \fBrawstats\fR

   708 .ad

   709 .sp .25

   710 .RS 4n

   711 Enables recording of raw-timestamp statistics information. This includes statistics records of all peers of a NTP server and of special signals, where present and configured. Each NTP message received from a peer or clock driver appends a line of the following form to the file generation set named \fBrawstats\fR:

   712 .LP

   713 \fB50928 2132.2543 128.4.1.1 128.4.1.20 3102453281.2584327000 3102453281.258622800031 02453332.2540806000 3102453332.2541458000\fR

   714 .LP

   715 The first two fields show the date (Modified Julian Day) and time (seconds and fraction past UTC midnight). The next two fields show the remote peer or clock address followed by the local address in dotted-quad notation, The final four fields show the originate, receive, transmit and final NTP timestamps in order. The timestamp values are as received and before processing by the various data smoothing and mitigation algorithms.

   716 .RE

   717 .sp .3

   718 .ne 2

   719 .mk

   720 .na

   721 \fBsysstats\fR

   722 .ad

   723 .sp .25

   724 .RS 4n

   725 Enables recording of \fBntpd\fR statistics counters on a periodic basis. Each hour a line of the following form is appended to the file generation set named \fBsysstats\fR:

   726 .LP

   727 \fB50928 2132.2543 36000 81965 0 9546 56 71793 512 540 10 147\fR

   728 .LP

   729 The first two fields show the date (Modified Julian Day) and time (seconds and fraction past UTC midnight). The remaining ten fields show the statistics counter values accumulated since the last generated line.

   730 .sp .3

   731 .ne 2

   732 .mk

   733 .na

   734 Time since restart \fB36000\fR:

   735 Time in hours since the system was last rebooted.

   736 .sp .3

   737 .ne 2

   738 .mk

   739 .na

   740 Packets received \fB81965\fR:

   741 Total number of packets received.

   742 .sp .3

   743 .ne 2

   744 .mk

   745 .na

   746 Packets processed \fB0\fR:

   747 Number of packets received in response to previous packets sent

   748 .sp .3

   749 .ne 2

   750 .mk

   751 .na

   752 Current version \fB9546\fR:

   753 Number of packets matching the current NTP version.

   754 .sp .3

   755 .ne 2

   756 .mk

   757 .na

   758 Previous version \fB56\fR:

   759 Number of packets matching the previous NTP version.

   760 .sp .3

   761 .ne 2

   762 .mk

   763 .na

   764 Bad version \fB71793\fR:

   765 Number of packets matching neither NTP version.

   766 .sp .3

   767 .ne 2

   768 .mk

   769 .na

   770 Access denied \fB512\fR:

   771 Number of packets denied access for any reason.

   772 .sp .3

   773 .ne 2

   774 .mk

   775 .na

   776 Bad length or format \fB540\fR:

   777 Number of packets with invalid length, format or port number.

   778 .sp .3

   779 .ne 2

   780 .mk

   781 .na

   782 Bad authentication \fB10\fR:

   783 Number of packets not verified as authentic.

   784 .sp .3

   785 .ne 2

   786 .mk

   787 .na

   788 Rate exceeded \fB147\fR:

   789 Number of packets discarded due to rate limitation.

   790 .RE

   791 .sp .3

   792 .ne 2

   793 .mk

   794 .na

   795 \fBstatsdir \fIdirectory_path\fP\fR

   796 .ad

   797 .sp .25

   798 .RS 4n

   799 Indicates the full path of a directory where statistics files should be created (see below). This keyword allows the (otherwise constant) \fBfilegen\fR filename prefix to be modified for file generation sets, which is useful for handling statistics logs.

   800 .RE

   801 .sp .3

   802 .ne 2

   803 .mk

   804 .na

   805 \fBfilegen \fIname\fP [file \fIfilename\fP] [type \fItypename\fP] [link | nolink] [enable | disable]\fR

   806 .ad

   807 .sp .25

   808 .RS 4n

   809 Configures setting of generation file set \fIname\fP. Generation file sets provide a means for handling files that are continuously growing during the lifetime of a server. Server statistics are a typical example for such files. Generation file sets provide access to a set of files used to store the actual data. At any time at most one element of the set is being written to. The type given specifies when and how data will be directed to a new element of the set. This way, information stored in elements of a file set that are currently unused are available for administrational operations without the risk of disturbing the operation of \fBntpd\fR. (Most important: they can be removed to free space for new data produced.)

   810 .ad

   811 .sp .25

   812 Note that this command can be sent from the \fBntpdc\fR program running at a remote location.

   813 .sp .3

   814 .ne 2

   815 .mk

   816 .na

   817 .TP

   818 \fIname\fR

   819 This is the type of the statistics records, as shown in the \fBstatistics\fR command.

   820 .TP

   821 \fBfile \fIfilename\fP\fR

   822 This is the file name for the statistics records. Filenames of set members are built from three concatenated elements \fIprefix\fP, \fIfilename\fP and \fIsuffix\fP:

   823 .TP

   824 \fIprefix\fP

   825 This is a constant filename path. It is not subject to modifications via the \fBfilegen\fR option. It is defined by the server, usually specified as a compile-time constant. It may, however, be configurable for individual file generation sets via other commands. For example, the prefix used with \fBloopstats\fR and \fBpeerstats\fR generation can be configured using the \fBstatsdir\fR option explained above.

   826 .TP

   827 \fIfilename\fP

   828 This string is directly concatenated to the prefix mentioned above (no intervening \fB/\fR (slash)). This can be modified using the \fBfile\fR argument to the \fBfilegen\fR statement. No \fB..\fR elements are allowed in this component to prevent filenames referring to parts outside the filesystem hierarchy denoted by \fBprefix\fR.

   829 .TP

   830 \fIsuffix\fP

   831 This part is reflects individual elements of a file set. It is generated according to the type of a file set.

   832 .TP

   833 \fBtype \fItypename\fP\fR

   834 A file generation set is characterized by its type. The following types are supported:

   835 .RS 6n

   836 .TP

   837 \fBnone\fR

   838 The file set is actually a single plain file.

   839 .TP

   840 \fBpid\fR

   841 One element of file set is used per incarnation of a \fBntpd\fR server. This type does not perform any changes to file set members during runtime, however it provides an easy way of separating files belonging to different \fBntpd\fR server incarnations. The set member filename is built by appending a \fB.\fR (dot) to concatenated \fIprefix\fP and \fIfilename\fP strings, and appending the decimal representation of the process ID of the \fBntpd\fR server process.

   842 .TP

   843 \fBday\fR

   844 One file generation set element is created per day. A day is defined as the period between 00:00 and 24:00 UTC. The file set member suffix consists of a \fB.\fR (dot) and a day specification in the form \fBYYYYMMdd. YYYY\fR is a 4-digit year number (e.g., 1992). \fBMM\fR is a two digit month number. \fBdd\fR is a two digit day number. Thus, all information written at 10 December 1992 would end up in a file named \fB\fIprefix filename\fP.19921210\fR.

   845 .TP

   846 \fBweek\fR

   847 Any file set member contains data related to a certain week of a year. The term week is defined by computing day-of-year modulo 7. Elements of such a file generation set are distinguished by appending the following suffix to the file set filename base: A dot, a 4-digit year number, the letter \fBW\fR, and a 2-digit week number. For example, information from January, 10th 1992 would end up in a file with suffix \fB.1992W1\fR.

   848 .TP

   849 \fBmonth\fR

   850 One generation file set element is generated per month. The file name suffix consists of a dot, a 4-digit year number, and a 2-digit month.

   851 .TP

   852 \fByear\fR

   853 One generation file element is generated per year. The filename suffix consists of a dot and a 4 digit year number.

   854 .TP

   855 \fBage\fR

   856 This type of file generation sets changes to a new element of the file set every 24 hours of server operation. The filename suffix consists of a dot, the letter \fBa\fR, and an 8-digit number. This number is taken to be the number of seconds the server is running at the start of the corresponding 24-hour period. Information is only written to a file generation by specifying \fBenable\fR; output is prevented by specifying \fBdisable\fR.

   857 .RE

   858 .sp .3

   859 .ne 2

   860 .mk

   861 .na

   862 .TP

   863 \fBlink | nolink\fR

   864 It is convenient to be able to access the current element of a file generation set by a fixed name. This feature is enabled by specifying \fBlink\fR and disabled using \fBnolink\fR. If \fBlink\fR is specified, a hard link from the current file set element to a file without suffix is created. When there is already a file with this name and the number of links of this file is one, it is renamed appending a dot, the letter \fBC\fR, and the pid of the \fBntpd\fR server process. When the number of links is greater than one, the file is unlinked. This allows the current file to be accessed by a constant name.

   865 .TP

   866 \fBenable | disable\fR

   867 Enables or disables the recording function.

   868 .RE

   869 .sp .3

   870 .ne 2

   871 .mk

   872 .na

   873 \fBbroadcastdelay \fIseconds\fP\fR

   874 .ad

   875 .sp .25

   876 .RS 4n

   877 The broadcast and multicast modes require a special calibration to determine the network delay between the local and remote servers. Ordinarily, this is done automatically by the initial protocol exchanges between the client and server. In some cases, the calibration procedure may fail due to network or server access controls, for example. This command specifies the default delay to be used under these circumstances. Typically (for Ethernet), a number between 0.003 and 0.007 seconds is appropriate. The default when this command is not used is 0.004 seconds.

   878 .RE

   879 .sp .3

   880 .ne 2

   881 .mk

   882 .na

   883 \fBcalldelay \fIdelay\fP\fR

   884 .ad

   885 .sp .25

   886 .RS 4n

   887 This option controls the delay in seconds between the first and second packets sent in burst or iburst mode to allow additional time for a modem or ISDN call to complete.

   888 .RE

   889 .sp .3

   890 .ne 2

   891 .mk

   892 .na

   893 \fBdriftfile \fIdriftfile\fP { \fItolerance\fP ]\fR

   894 .ad

   895 .sp .25

   896 .RS 4n

   897 This command specifies the complete path and name of the file used to record the frequency of the local clock oscillator. This is the same operation as the \fB-f\fR command linke option. If the file exists, it is read at startup in order to set the initial frequency and then updated once per hour with the current frequency computed by the daemon. If the file name is specified, but the file itself does not exist, the starts with an initial frequency of zero and creates the file when writing it for the first time. If this command is not given, the daemon will always start with an initial frequency of zero.

   898 .LP

   899 The file format consists of a single line containing a single floating point number, which records the frequency offset measured in parts-per-million (PPM). The file is updated by first writing the current drift value into a temporary file and then renaming this file to replace the old version. This implies that \fBntpd\fR must have write permission for the directory the drift file is located in, and that file system links, symbolic or otherwise, should be avoided.

   900 .LP

   901 The parameter \fBtolerance\fR is the wander threshold to skip writing the new value. If the value of wander computed from recent frequency changes is greater than this threshold the file will be updated once per hour. If below the threshold, the file will not be written.

   902 .RE

   903 .sp .3

   904 .ne 2

   905 .mk

   906 .na

   907 \fBenable [ auth | bclient | calibrate | kernel | monitor | ntp | pps | stats]\fR

   908 .br

   909 \fBdisable [ auth | bclient | calibrate | kernel | monitor | ntp | pps | stats ]\fR

   910 .ad

   911 .sp .25

   912 .RS 4n

   913 Provides a way to enable or disable various system options. Flags not mentioned are unaffected. Note that all of these flags can be controlled remotely using the \fBntpdc\fR utility program.

   914 .RE

   915 .sp .3

   916 .ne 2

   917 .mk

   918 .na

   919 \fBauth\fR

   920 .ad

   921 .sp .25

   922 .RS 4n

   923 Enables the server to synchronize with unconfigured peers only if the peer has been correctly authenticated using either public key or private key cryptography. The default for this flag is enable.

   924 .RE

   925 .sp .3

   926 .ne 2

   927 .mk

   928 .na

   929 \fBbclient\fR

   930 .ad

   931 .sp .25

   932 .RS 4n

   933 Enables the server to listen for a message from a broadcast or multicast server, as in the \fBmulticastclient\fR command with default address. The default for this flag is disable.

   934 .RE

   935 .sp .3

   936 .ne 2

   937 .mk

   938 .na

   939 \fBcalibrate\fR

   940 .ad

   941 .sp .25

   942 .RS 4n

   943 Enables the calibrate feature for reference clocks. The default for this flag is disable.

   944 .RE

   945 .sp .3

   946 .ne 2

   947 .mk

   948 .na

   949 \fBkernel\fR

   950 .ad

   951 .sp .25

   952 .RS 4n

   953 Enables the kernel time discipline, if available. The default for this flag is enable if support is available, otherwise disable.

   954 .RE

   955 .sp .3

   956 .ne 2

   957 .mk

   958 .na

   959 \fBmonitor\fR

   960 .ad

   961 .sp .25

   962 .RS 4n

   963 Enables the monitoring facility. See the \fBntpdc\fR program and the \fBmonlist\fR command or further information. The default for this flag is enable.

   964 .RE

   965 .sp .3

   966 .ne 2

   967 .mk

   968 .na

   969 \fBntp\fR

   970 .ad

   971 .sp .25

   972 .RS 4n

   973 Enables time and frequency discipline. In effect, this switch opens and closes the feedback loop, which is useful for testing. The default for this flag is enable.

   974 .RE

   975 .sp .3

   976 .ne 2

   977 .mk

   978 .na

   979 \fBpps\fR

   980 .ad

   981 .sp .25

   982 .RS 4n

   983 Enables the pulse-per-second (PPS) signal when frequency and time is disciplined by the precision time kernel modifications. See the Kernel Model for Precision Timekeeping page at file:///usr/share/doc/ntp/kern.html for further information. The default for this flag is disable.

   984 .RE

   985 .sp .3

   986 .ne 2

   987 .mk

   988 .na

   989 \fBstats\fR

   990 .ad

   991 .sp .25

   992 .RS 4n

   993 Enables the statistics facility. The default for this flag is disable

   994 .RE

   995 .sp .3

   996 .ne 2

   997 .mk

   998 .na

   999 \fBincludefile \fIincludefile\fP\fR

  1000 .ad

  1001 .sp .25

  1002 .RS 4n

  1003 This command allows additional configuration commands to be included from a separate file. Include files may be nested to a depth of five; upon reaching the end of any include file, command processing resumes in the previous configuration file. This option is useful for sites that run \fBntpd\fR on multiple hosts, with (mostly) common options (e.g., a restriction list).

  1004 .RE

  1005 .sp .3

  1006 .ne 2

  1007 .mk

  1008 .na

  1009 \fBlogconfig \fIconfigkeyword\fP\fR

  1010 .ad

  1011 .sp .25

  1012 .RS 4n

  1013 This command controls the amount and type of output written to the system \fBsyslog\fR facility or the alternate \fBlogfile\fR log file. All \fIconfigkeyword\fP keywords can be prefixed with \fB=\fR, \fB+\fR and \fB-\fR, where \fB=\fR sets the \fBsyslogmask\fR, \fB+\fR adds and \fB-\fR removes messages. \fBsyslog messages\fR can be controlled in four classes (\fBclock\fR, \fBpeer\fR, \fBsys\fR and \fBsync\fR). Within these classes four types of messages can be controlled: informational messages (\fBinfo\fR), event messages (\fBevents\fR), statistics messages (\fBstatistics\fR) and status messages (\fBstatus\fR).

  1014 .LP

  1015 Configuration keywords are formed by concatenating the message class with the event class. The \fBall\fR prefix can be used instead of a message class. A message class may also be followed by the \fBall\fR keyword to enable/disable all messages of the respective message class. By default, \fBlogconfig\fR output is set to \fBallsync\fR.

  1016 .LP

  1017 Thus, a minimal log configuration could look like this:

  1018 .LP

  1019 \fBlogconfig =syncstatus +sysevents\fR

  1020 .LP

  1021 This would just list the synchronizations state of \fBntpd\fR and the major system events. For a simple reference server, the following minimum message configuration could be useful:

  1022 .LP

  1023 \fBlogconfig =allsync +allclock\fR

  1024 .LP

  1025 This configuration will list all clock information and synchronization information. All other events and messages about peers, system events and so on is suppressed.

  1026 .RE

  1027 .sp .3

  1028 .ne 2

  1029 .mk

  1030 .na

  1031 \fBlogfile \fIlogfile\fP\fR

  1032 .ad

  1033 .sp .25

  1034 .RS 4n

  1035 .LP

  1036 This command specifies the location of an alternate log file to be used instead of the default system \fBsyslog\fR facility. This is the same operation as the \fB-l \fRcommand line option.

  1037 .RE

  1038 .sp .3

  1039 .ne 2

  1040 .mk

  1041 .na

  1042 \fBphone \fIdial\fP1 \fIdial\fP2 ...\fR

  1043 .ad

  1044 .sp .25

  1045 .RS 4n

  1046 This command is used in conjunction with the ACTS modem driver (type 18). The arguments consist of a maximum of 10 telephone numbers used to dial USNO, NIST or European time services. The Hayes command ATDT is normally prepended to the number, which can contain other modem control codes as well.

  1047 .RE

  1048 .sp .3

  1049 .ne 2

  1050 .mk

  1051 .na

  1052 \fBsetvar \fIvariable\fP [default]\fR

  1053 .ad

  1054 .sp .25

  1055 .RS 4n

  1056 This command adds an additional system variable. These variables can be used to distribute additional information such as the access policy. If the variable of the form \fB\fIname\fP = \fIvalue\fP\fR is followed by the \fBdefault\fR keyword, the variable will be listed as part of the default system variables (\fBntpq rv\fR command). These additional variables serve informational purposes only. They are not related to the protocol other that they can be listed. The known protocol variables will always override any variables defined via the \fBsetvar\fR mechanism. There are three special variables that contain the names of all variable of the same group. The \fBsys_var_list\fR holds the names of all system variables. The \fBpeer_var_list\fR holds the names of all peer variables and the \fBclock_var_list\fR holds the names of the reference clock variables.

  1057 .RE

  1058 .sp .3

  1059 .ne 2

  1060 .mk

  1061 .na

  1062 \fBtinker [ allan \fIallan\fP | dispersion \fIdispersion\fP | freq \fIfreq\fP | huffpuff \fIhuffpuff\fP | panic \fIpanic\fP | step \fIstep\fP | stepout \fIstepout\fP ]\fR

  1063 .ad

  1064 .sp .25

  1065 .RS 4n

  1066 This command can be used to alter several system variables in very exceptional circumstances. It should occur in the configuration file before any other configuration options. The default values of these variables have been carefully optimized for a wide range of network speeds and reliability expectations. In general, they interact in intricate ways that are hard to predict and some combinations can result in some very nasty behavior. Very rarely is it necessary to change the default values; but, some folks can't resist twisting the knobs anyway and this command is for them. Emphasis added: twisters are on their own and can expect no help from the support group.

  1067 .LP

  1068 The variables operate as follows:

  1069 .sp .3

  1070 .ne 2

  1071 .mk

  1072 .na

  1073 \fBallan \fIallan\fP\fR

  1074 .ad

  1075 .sp .25

  1076 .RS 6n

  1077 The argument becomes the new value for the Allan intercept, which is a parameter of the PLL/FLL clock discipline algorithm. The value is in  seconds with default 1500 s, which is appropriate for most computer clocks.

  1078 .RE

  1079 .sp .3

  1080 .ne 2

  1081 .mk

  1082 .na

  1083 \fBdispersion \fIdispersion\fP\fR

  1084 .ad

  1085 .sp .25

  1086 .RS 6n

  1087 The argument becomes the new value for the dispersion increase rate, normally .000015 s/s.

  1088 .RE

  1089 .sp .3

  1090 .ne 2

  1091 .mk

  1092 .na

  1093 \fBfreq \fIfreq\fP\fR

  1094 .ad

  1095 .sp .25

  1096 .RS 6n

  1097 The argument becomes the initial value of the frequency offset in parts-per-million. This overrides the value in the frequency file, if present, and avoids the initial training state if it is not.

  1098 .RE

  1099 .sp .3

  1100 .ne 2

  1101 .mk

  1102 .na

  1103 \fBhuffpuff \fIhuffpuff\fP\fR

  1104 .ad

  1105 .sp .25

  1106 .RS 6n

  1107 The argument becomes the new value for the experimental huff-n'-puff filter span, which determines the most recent interval the algorithm will search for a minimum delay. The lower limit is 900 s (15 m), but a more reasonable value is 7200 (2 hours). There is no default, since the filter is not enabled unless this command is given.

  1108 .RE

  1109 .sp .3

  1110 .ne 2

  1111 .mk

  1112 .na

  1113 \fBpanic \fIpanic\fP\fR

  1114 .ad

  1115 .sp .25

  1116 .RS 6n

  1117 The argument is the panic threshold, by default 1000 s. If set to zero, the panic sanity check is disabled and a clock offset of any value will be accepted.

  1118 .RE

  1119 .sp .3

  1120 .ne 2

  1121 .mk

  1122 .na

  1123 \fBstep \fIstep\fP\fR

  1124 .ad

  1125 .sp .25

  1126 .RS 6n

  1127 The argument is the step threshold, by default 0.128 s. It can be set to any positive number in seconds. If set to zero, step adjustments will never occur. Note: The kernel time discipline is disabled if the step threshold is set to zero or greater than the default.

  1128 .RE

  1129 .sp .3

  1130 .ne 2

  1131 .mk

  1132 .na

  1133 \fBstepout \fIstepout\fP\fR

  1134 .ad