ntp.conf.def revision 275970
1275970Scy/* -*- Mode: Text -*- */ 2275970Scy 3275970Scyautogen definitions options; 4275970Scy 5275970Scy#include copyright.def 6275970Scy 7275970Scy// We want the synopsis to be "/etc/ntp.conf" but we need the prog-name 8275970Scy// to be ntp.conf - the latter is also how autogen produces the output 9275970Scy// file name. 10275970Scyprog-name = "ntp.conf"; 11275970Scyfile-path = "/etc/ntp.conf"; 12275970Scyprog-title = "Network Time Protocol (NTP) daemon configuration file format"; 13275970Scy 14275970Scy/* explain: Additional information whenever the usage routine is invoked */ 15275970Scyexplain = <<- _END_EXPLAIN 16275970Scy _END_EXPLAIN; 17275970Scy 18275970Scydoc-section = { 19275970Scy ds-type = 'DESCRIPTION'; 20275970Scy ds-format = 'mdoc'; 21275970Scy ds-text = <<- _END_PROG_MDOC_DESCRIP 22275970ScyThe 23275970Scy.Nm 24275970Scyconfiguration file is read at initial startup by the 25275970Scy.Xr ntpd 1ntpdmdoc 26275970Scydaemon in order to specify the synchronization sources, 27275970Scymodes and other related information. 28275970ScyUsually, it is installed in the 29275970Scy.Pa /etc 30275970Scydirectory, 31275970Scybut could be installed elsewhere 32275970Scy(see the daemon's 33275970Scy.Fl c 34275970Scycommand line option). 35275970Scy.Pp 36275970ScyThe file format is similar to other 37275970Scy.Ux 38275970Scyconfiguration files. 39275970ScyComments begin with a 40275970Scy.Ql # 41275970Scycharacter and extend to the end of the line; 42275970Scyblank lines are ignored. 43275970ScyConfiguration commands consist of an initial keyword 44275970Scyfollowed by a list of arguments, 45275970Scysome of which may be optional, separated by whitespace. 46275970ScyCommands may not be continued over multiple lines. 47275970ScyArguments may be host names, 48275970Scyhost addresses written in numeric, dotted-quad form, 49275970Scyintegers, floating point numbers (when specifying times in seconds) 50275970Scyand text strings. 51275970Scy.Pp 52275970ScyThe rest of this page describes the configuration and control options. 53275970ScyThe 54275970Scy.Qq Notes on Configuring NTP and Setting up an NTP Subnet 55275970Scypage 56275970Scy(available as part of the HTML documentation 57275970Scyprovided in 58275970Scy.Pa /usr/share/doc/ntp ) 59275970Scycontains an extended discussion of these options. 60275970ScyIn addition to the discussion of general 61275970Scy.Sx Configuration Options , 62275970Scythere are sections describing the following supported functionality 63275970Scyand the options used to control it: 64275970Scy.Bl -bullet -offset indent 65275970Scy.It 66275970Scy.Sx Authentication Support 67275970Scy.It 68275970Scy.Sx Monitoring Support 69275970Scy.It 70275970Scy.Sx Access Control Support 71275970Scy.It 72275970Scy.Sx Automatic NTP Configuration Options 73275970Scy.It 74275970Scy.Sx Reference Clock Support 75275970Scy.It 76275970Scy.Sx Miscellaneous Options 77275970Scy.El 78275970Scy.Pp 79275970ScyFollowing these is a section describing 80275970Scy.Sx Miscellaneous Options . 81275970ScyWhile there is a rich set of options available, 82275970Scythe only required option is one or more 83275970Scy.Ic pool , 84275970Scy.Ic server , 85275970Scy.Ic peer , 86275970Scy.Ic broadcast 87275970Scyor 88275970Scy.Ic manycastclient 89275970Scycommands. 90275970Scy.Sh Configuration Support 91275970ScyFollowing is a description of the configuration commands in 92275970ScyNTPv4. 93275970ScyThese commands have the same basic functions as in NTPv3 and 94275970Scyin some cases new functions and new arguments. 95275970ScyThere are two 96275970Scyclasses of commands, configuration commands that configure a 97275970Scypersistent association with a remote server or peer or reference 98275970Scyclock, and auxiliary commands that specify environmental variables 99275970Scythat control various related operations. 100275970Scy.Ss Configuration Commands 101275970ScyThe various modes are determined by the command keyword and the 102275970Scytype of the required IP address. 103275970ScyAddresses are classed by type as 104275970Scy(s) a remote server or peer (IPv4 class A, B and C), (b) the 105275970Scybroadcast address of a local interface, (m) a multicast address (IPv4 106275970Scyclass D), or (r) a reference clock address (127.127.x.x). 107275970ScyNote that 108275970Scyonly those options applicable to each command are listed below. 109275970ScyUse 110275970Scyof options not listed may not be caught as an error, but may result 111275970Scyin some weird and even destructive behavior. 112275970Scy.Pp 113275970ScyIf the Basic Socket Interface Extensions for IPv6 (RFC-2553) 114275970Scyis detected, support for the IPv6 address family is generated 115275970Scyin addition to the default support of the IPv4 address family. 116275970ScyIn a few cases, including the reslist billboard generated 117275970Scyby ntpdc, IPv6 addresses are automatically generated. 118275970ScyIPv6 addresses can be identified by the presence of colons 119275970Scy.Dq \&: 120275970Scyin the address field. 121275970ScyIPv6 addresses can be used almost everywhere where 122275970ScyIPv4 addresses can be used, 123275970Scywith the exception of reference clock addresses, 124275970Scywhich are always IPv4. 125275970Scy.Pp 126275970ScyNote that in contexts where a host name is expected, a 127275970Scy.Fl 4 128275970Scyqualifier preceding 129275970Scythe host name forces DNS resolution to the IPv4 namespace, 130275970Scywhile a 131275970Scy.Fl 6 132275970Scyqualifier forces DNS resolution to the IPv6 namespace. 133275970ScySee IPv6 references for the 134275970Scyequivalent classes for that address family. 135275970Scy.Bl -tag -width indent 136275970Scy.It Xo Ic pool Ar address 137275970Scy.Op Cm burst 138275970Scy.Op Cm iburst 139275970Scy.Op Cm version Ar version 140275970Scy.Op Cm prefer 141275970Scy.Op Cm minpoll Ar minpoll 142275970Scy.Op Cm maxpoll Ar maxpoll 143275970Scy.Xc 144275970Scy.It Xo Ic server Ar address 145275970Scy.Op Cm key Ar key \&| Cm autokey 146275970Scy.Op Cm burst 147275970Scy.Op Cm iburst 148275970Scy.Op Cm version Ar version 149275970Scy.Op Cm prefer 150275970Scy.Op Cm minpoll Ar minpoll 151275970Scy.Op Cm maxpoll Ar maxpoll 152275970Scy.Xc 153275970Scy.It Xo Ic peer Ar address 154275970Scy.Op Cm key Ar key \&| Cm autokey 155275970Scy.Op Cm version Ar version 156275970Scy.Op Cm prefer 157275970Scy.Op Cm minpoll Ar minpoll 158275970Scy.Op Cm maxpoll Ar maxpoll 159275970Scy.Xc 160275970Scy.It Xo Ic broadcast Ar address 161275970Scy.Op Cm key Ar key \&| Cm autokey 162275970Scy.Op Cm version Ar version 163275970Scy.Op Cm prefer 164275970Scy.Op Cm minpoll Ar minpoll 165275970Scy.Op Cm ttl Ar ttl 166275970Scy.Xc 167275970Scy.It Xo Ic manycastclient Ar address 168275970Scy.Op Cm key Ar key \&| Cm autokey 169275970Scy.Op Cm version Ar version 170275970Scy.Op Cm prefer 171275970Scy.Op Cm minpoll Ar minpoll 172275970Scy.Op Cm maxpoll Ar maxpoll 173275970Scy.Op Cm ttl Ar ttl 174275970Scy.Xc 175275970Scy.El 176275970Scy.Pp 177275970ScyThese five commands specify the time server name or address to 178275970Scybe used and the mode in which to operate. 179275970ScyThe 180275970Scy.Ar address 181275970Scycan be 182275970Scyeither a DNS name or an IP address in dotted-quad notation. 183275970ScyAdditional information on association behavior can be found in the 184275970Scy.Qq Association Management 185275970Scypage 186275970Scy(available as part of the HTML documentation 187275970Scyprovided in 188275970Scy.Pa /usr/share/doc/ntp ) . 189275970Scy.Bl -tag -width indent 190275970Scy.It Ic pool 191275970ScyFor type s addresses, this command mobilizes a persistent 192275970Scyclient mode association with a number of remote servers. 193275970ScyIn this mode the local clock can synchronized to the 194275970Scyremote server, but the remote server can never be synchronized to 195275970Scythe local clock. 196275970Scy.It Ic server 197275970ScyFor type s and r addresses, this command mobilizes a persistent 198275970Scyclient mode association with the specified remote server or local 199275970Scyradio clock. 200275970ScyIn this mode the local clock can synchronized to the 201275970Scyremote server, but the remote server can never be synchronized to 202275970Scythe local clock. 203275970ScyThis command should 204275970Scy.Em not 205275970Scybe used for type 206275970Scyb or m addresses. 207275970Scy.It Ic peer 208275970ScyFor type s addresses (only), this command mobilizes a 209275970Scypersistent symmetric-active mode association with the specified 210275970Scyremote peer. 211275970ScyIn this mode the local clock can be synchronized to 212275970Scythe remote peer or the remote peer can be synchronized to the local 213275970Scyclock. 214275970ScyThis is useful in a network of servers where, depending on 215275970Scyvarious failure scenarios, either the local or remote peer may be 216275970Scythe better source of time. 217275970ScyThis command should NOT be used for type 218275970Scyb, m or r addresses. 219275970Scy.It Ic broadcast 220275970ScyFor type b and m addresses (only), this 221275970Scycommand mobilizes a persistent broadcast mode association. 222275970ScyMultiple 223275970Scycommands can be used to specify multiple local broadcast interfaces 224275970Scy(subnets) and/or multiple multicast groups. 225275970ScyNote that local 226275970Scybroadcast messages go only to the interface associated with the 227275970Scysubnet specified, but multicast messages go to all interfaces. 228275970ScyIn broadcast mode the local server sends periodic broadcast 229275970Scymessages to a client population at the 230275970Scy.Ar address 231275970Scyspecified, which is usually the broadcast address on (one of) the 232275970Scylocal network(s) or a multicast address assigned to NTP. 233275970ScyThe IANA 234275970Scyhas assigned the multicast group address IPv4 224.0.1.1 and 235275970ScyIPv6 ff05::101 (site local) exclusively to 236275970ScyNTP, but other nonconflicting addresses can be used to contain the 237275970Scymessages within administrative boundaries. 238275970ScyOrdinarily, this 239275970Scyspecification applies only to the local server operating as a 240275970Scysender; for operation as a broadcast client, see the 241275970Scy.Ic broadcastclient 242275970Scyor 243275970Scy.Ic multicastclient 244275970Scycommands 245275970Scybelow. 246275970Scy.It Ic manycastclient 247275970ScyFor type m addresses (only), this command mobilizes a 248275970Scymanycast client mode association for the multicast address 249275970Scyspecified. 250275970ScyIn this case a specific address must be supplied which 251275970Scymatches the address used on the 252275970Scy.Ic manycastserver 253275970Scycommand for 254275970Scythe designated manycast servers. 255275970ScyThe NTP multicast address 256275970Scy224.0.1.1 assigned by the IANA should NOT be used, unless specific 257275970Scymeans are taken to avoid spraying large areas of the Internet with 258275970Scythese messages and causing a possibly massive implosion of replies 259275970Scyat the sender. 260275970ScyThe 261275970Scy.Ic manycastserver 262275970Scycommand specifies that the local server 263275970Scyis to operate in client mode with the remote servers that are 264275970Scydiscovered as the result of broadcast/multicast messages. 265275970ScyThe 266275970Scyclient broadcasts a request message to the group address associated 267275970Scywith the specified 268275970Scy.Ar address 269275970Scyand specifically enabled 270275970Scyservers respond to these messages. 271275970ScyThe client selects the servers 272275970Scyproviding the best time and continues as with the 273275970Scy.Ic server 274275970Scycommand. 275275970ScyThe remaining servers are discarded as if never 276275970Scyheard. 277275970Scy.El 278275970Scy.Pp 279275970ScyOptions: 280275970Scy.Bl -tag -width indent 281275970Scy.It Cm autokey 282275970ScyAll packets sent to and received from the server or peer are to 283275970Scyinclude authentication fields encrypted using the autokey scheme 284275970Scydescribed in 285275970Scy.Sx Authentication Options . 286275970Scy.It Cm burst 287275970Scywhen the server is reachable, send a burst of eight packets 288275970Scyinstead of the usual one. 289275970ScyThe packet spacing is normally 2 s; 290275970Scyhowever, the spacing between the first and second packets 291275970Scycan be changed with the calldelay command to allow 292275970Scyadditional time for a modem or ISDN call to complete. 293275970ScyThis is designed to improve timekeeping quality 294275970Scywith the 295275970Scy.Ic server 296275970Scycommand and s addresses. 297275970Scy.It Cm iburst 298275970ScyWhen the server is unreachable, send a burst of eight packets 299275970Scyinstead of the usual one. 300275970ScyThe packet spacing is normally 2 s; 301275970Scyhowever, the spacing between the first two packets can be 302275970Scychanged with the calldelay command to allow 303275970Scyadditional time for a modem or ISDN call to complete. 304275970ScyThis is designed to speed the initial synchronization 305275970Scyacquisition with the 306275970Scy.Ic server 307275970Scycommand and s addresses and when 308275970Scy.Xr ntpd 1ntpdmdoc 309275970Scyis started with the 310275970Scy.Fl q 311275970Scyoption. 312275970Scy.It Cm key Ar key 313275970ScyAll packets sent to and received from the server or peer are to 314275970Scyinclude authentication fields encrypted using the specified 315275970Scy.Ar key 316275970Scyidentifier with values from 1 to 65534, inclusive. 317275970ScyThe 318275970Scydefault is to include no encryption field. 319275970Scy.It Cm minpoll Ar minpoll 320275970Scy.It Cm maxpoll Ar maxpoll 321275970ScyThese options specify the minimum and maximum poll intervals 322275970Scyfor NTP messages, as a power of 2 in seconds 323275970ScyThe maximum poll 324275970Scyinterval defaults to 10 (1,024 s), but can be increased by the 325275970Scy.Cm maxpoll 326275970Scyoption to an upper limit of 17 (36.4 h). 327275970ScyThe 328275970Scyminimum poll interval defaults to 6 (64 s), but can be decreased by 329275970Scythe 330275970Scy.Cm minpoll 331275970Scyoption to a lower limit of 4 (16 s). 332275970Scy.It Cm noselect 333275970ScyMarks the server as unused, except for display purposes. 334275970ScyThe server is discarded by the selection algroithm. 335275970Scy.It Cm prefer 336275970ScyMarks the server as preferred. 337275970ScyAll other things being equal, 338275970Scythis host will be chosen for synchronization among a set of 339275970Scycorrectly operating hosts. 340275970ScySee the 341275970Scy.Qq Mitigation Rules and the prefer Keyword 342275970Scypage 343275970Scy(available as part of the HTML documentation 344275970Scyprovided in 345275970Scy.Pa /usr/share/doc/ntp ) 346275970Scyfor further information. 347275970Scy.It Cm ttl Ar ttl 348275970ScyThis option is used only with broadcast server and manycast 349275970Scyclient modes. 350275970ScyIt specifies the time-to-live 351275970Scy.Ar ttl 352275970Scyto 353275970Scyuse on broadcast server and multicast server and the maximum 354275970Scy.Ar ttl 355275970Scyfor the expanding ring search with manycast 356275970Scyclient packets. 357275970ScySelection of the proper value, which defaults to 358275970Scy127, is something of a black art and should be coordinated with the 359275970Scynetwork administrator. 360275970Scy.It Cm version Ar version 361275970ScySpecifies the version number to be used for outgoing NTP 362275970Scypackets. 363275970ScyVersions 1-4 are the choices, with version 4 the 364275970Scydefault. 365275970Scy.El 366275970Scy.Ss Auxiliary Commands 367275970Scy.Bl -tag -width indent 368275970Scy.It Ic broadcastclient 369275970ScyThis command enables reception of broadcast server messages to 370275970Scyany local interface (type b) address. 371275970ScyUpon receiving a message for 372275970Scythe first time, the broadcast client measures the nominal server 373275970Scypropagation delay using a brief client/server exchange with the 374275970Scyserver, then enters the broadcast client mode, in which it 375275970Scysynchronizes to succeeding broadcast messages. 376275970ScyNote that, in order 377275970Scyto avoid accidental or malicious disruption in this mode, both the 378275970Scyserver and client should operate using symmetric-key or public-key 379275970Scyauthentication as described in 380275970Scy.Sx Authentication Options . 381275970Scy.It Ic manycastserver Ar address ... 382275970ScyThis command enables reception of manycast client messages to 383275970Scythe multicast group address(es) (type m) specified. 384275970ScyAt least one 385275970Scyaddress is required, but the NTP multicast address 224.0.1.1 386275970Scyassigned by the IANA should NOT be used, unless specific means are 387275970Scytaken to limit the span of the reply and avoid a possibly massive 388275970Scyimplosion at the original sender. 389275970ScyNote that, in order to avoid 390275970Scyaccidental or malicious disruption in this mode, both the server 391275970Scyand client should operate using symmetric-key or public-key 392275970Scyauthentication as described in 393275970Scy.Sx Authentication Options . 394275970Scy.It Ic multicastclient Ar address ... 395275970ScyThis command enables reception of multicast server messages to 396275970Scythe multicast group address(es) (type m) specified. 397275970ScyUpon receiving 398275970Scya message for the first time, the multicast client measures the 399275970Scynominal server propagation delay using a brief client/server 400275970Scyexchange with the server, then enters the broadcast client mode, in 401275970Scywhich it synchronizes to succeeding multicast messages. 402275970ScyNote that, 403275970Scyin order to avoid accidental or malicious disruption in this mode, 404275970Scyboth the server and client should operate using symmetric-key or 405275970Scypublic-key authentication as described in 406275970Scy.Sx Authentication Options . 407275970Scy.El 408275970Scy.Sh Authentication Support 409275970ScyAuthentication support allows the NTP client to verify that the 410275970Scyserver is in fact known and trusted and not an intruder intending 411275970Scyaccidentally or on purpose to masquerade as that server. 412275970ScyThe NTPv3 413275970Scyspecification RFC-1305 defines a scheme which provides 414275970Scycryptographic authentication of received NTP packets. 415275970ScyOriginally, 416275970Scythis was done using the Data Encryption Standard (DES) algorithm 417275970Scyoperating in Cipher Block Chaining (CBC) mode, commonly called 418275970ScyDES-CBC. 419275970ScySubsequently, this was replaced by the RSA Message Digest 420275970Scy5 (MD5) algorithm using a private key, commonly called keyed-MD5. 421275970ScyEither algorithm computes a message digest, or one-way hash, which 422275970Scycan be used to verify the server has the correct private key and 423275970Scykey identifier. 424275970Scy.Pp 425275970ScyNTPv4 retains the NTPv3 scheme, properly described as symmetric key 426275970Scycryptography and, in addition, provides a new Autokey scheme 427275970Scybased on public key cryptography. 428275970ScyPublic key cryptography is generally considered more secure 429275970Scythan symmetric key cryptography, since the security is based 430275970Scyon a private value which is generated by each server and 431275970Scynever revealed. 432275970ScyWith Autokey all key distribution and 433275970Scymanagement functions involve only public values, which 434275970Scyconsiderably simplifies key distribution and storage. 435275970ScyPublic key management is based on X.509 certificates, 436275970Scywhich can be provided by commercial services or 437275970Scyproduced by utility programs in the OpenSSL software library 438275970Scyor the NTPv4 distribution. 439275970Scy.Pp 440275970ScyWhile the algorithms for symmetric key cryptography are 441275970Scyincluded in the NTPv4 distribution, public key cryptography 442275970Scyrequires the OpenSSL software library to be installed 443275970Scybefore building the NTP distribution. 444275970ScyDirections for doing that 445275970Scyare on the Building and Installing the Distribution page. 446275970Scy.Pp 447275970ScyAuthentication is configured separately for each association 448275970Scyusing the 449275970Scy.Cm key 450275970Scyor 451275970Scy.Cm autokey 452275970Scysubcommand on the 453275970Scy.Ic peer , 454275970Scy.Ic server , 455275970Scy.Ic broadcast 456275970Scyand 457275970Scy.Ic manycastclient 458275970Scyconfiguration commands as described in 459275970Scy.Sx Configuration Options 460275970Scypage. 461275970ScyThe authentication 462275970Scyoptions described below specify the locations of the key files, 463275970Scyif other than default, which symmetric keys are trusted 464275970Scyand the interval between various operations, if other than default. 465275970Scy.Pp 466275970ScyAuthentication is always enabled, 467275970Scyalthough ineffective if not configured as 468275970Scydescribed below. 469275970ScyIf a NTP packet arrives 470275970Scyincluding a message authentication 471275970Scycode (MAC), it is accepted only if it 472275970Scypasses all cryptographic checks. 473275970ScyThe 474275970Scychecks require correct key ID, key value 475275970Scyand message digest. 476275970ScyIf the packet has 477275970Scybeen modified in any way or replayed 478275970Scyby an intruder, it will fail one or more 479275970Scyof these checks and be discarded. 480275970ScyFurthermore, the Autokey scheme requires a 481275970Scypreliminary protocol exchange to obtain 482275970Scythe server certificate, verify its 483275970Scycredentials and initialize the protocol 484275970Scy.Pp 485275970ScyThe 486275970Scy.Cm auth 487275970Scyflag controls whether new associations or 488275970Scyremote configuration commands require cryptographic authentication. 489275970ScyThis flag can be set or reset by the 490275970Scy.Ic enable 491275970Scyand 492275970Scy.Ic disable 493275970Scycommands and also by remote 494275970Scyconfiguration commands sent by a 495275970Scy.Xr ntpdc 1ntpdcmdoc 496275970Scyprogram running in 497275970Scyanother machine. 498275970ScyIf this flag is enabled, which is the default 499275970Scycase, new broadcast client and symmetric passive associations and 500275970Scyremote configuration commands must be cryptographically 501275970Scyauthenticated using either symmetric key or public key cryptography. 502275970ScyIf this 503275970Scyflag is disabled, these operations are effective 504275970Scyeven if not cryptographic 505275970Scyauthenticated. 506275970ScyIt should be understood 507275970Scythat operating with the 508275970Scy.Ic auth 509275970Scyflag disabled invites a significant vulnerability 510275970Scywhere a rogue hacker can 511275970Scymasquerade as a falseticker and seriously 512275970Scydisrupt system timekeeping. 513275970ScyIt is 514275970Scyimportant to note that this flag has no purpose 515275970Scyother than to allow or disallow 516275970Scya new association in response to new broadcast 517275970Scyand symmetric active messages 518275970Scyand remote configuration commands and, in particular, 519275970Scythe flag has no effect on 520275970Scythe authentication process itself. 521275970Scy.Pp 522275970ScyAn attractive alternative where multicast support is available 523275970Scyis manycast mode, in which clients periodically troll 524275970Scyfor servers as described in the 525275970Scy.Sx Automatic NTP Configuration Options 526275970Scypage. 527275970ScyEither symmetric key or public key 528275970Scycryptographic authentication can be used in this mode. 529275970ScyThe principle advantage 530275970Scyof manycast mode is that potential servers need not be 531275970Scyconfigured in advance, 532275970Scysince the client finds them during regular operation, 533275970Scyand the configuration 534275970Scyfiles for all clients can be identical. 535275970Scy.Pp 536275970ScyThe security model and protocol schemes for 537275970Scyboth symmetric key and public key 538275970Scycryptography are summarized below; 539275970Scyfurther details are in the briefings, papers 540275970Scyand reports at the NTP project page linked from 541275970Scy.Li http://www.ntp.org/ . 542275970Scy.Ss Symmetric-Key Cryptography 543275970ScyThe original RFC-1305 specification allows any one of possibly 544275970Scy65,534 keys, each distinguished by a 32-bit key identifier, to 545275970Scyauthenticate an association. 546275970ScyThe servers and clients involved must 547275970Scyagree on the key and key identifier to 548275970Scyauthenticate NTP packets. 549275970ScyKeys and 550275970Scyrelated information are specified in a key 551275970Scyfile, usually called 552275970Scy.Pa ntp.keys , 553275970Scywhich must be distributed and stored using 554275970Scysecure means beyond the scope of the NTP protocol itself. 555275970ScyBesides the keys used 556275970Scyfor ordinary NTP associations, 557275970Scyadditional keys can be used as passwords for the 558275970Scy.Xr ntpq 1ntpqmdoc 559275970Scyand 560275970Scy.Xr ntpdc 1ntpdcmdoc 561275970Scyutility programs. 562275970Scy.Pp 563275970ScyWhen 564275970Scy.Xr ntpd 1ntpdmdoc 565275970Scyis first started, it reads the key file specified in the 566275970Scy.Ic keys 567275970Scyconfiguration command and installs the keys 568275970Scyin the key cache. 569275970ScyHowever, 570275970Scyindividual keys must be activated with the 571275970Scy.Ic trusted 572275970Scycommand before use. 573275970ScyThis 574275970Scyallows, for instance, the installation of possibly 575275970Scyseveral batches of keys and 576275970Scythen activating or deactivating each batch 577275970Scyremotely using 578275970Scy.Xr ntpdc 1ntpdcmdoc . 579275970ScyThis also provides a revocation capability that can be used 580275970Scyif a key becomes compromised. 581275970ScyThe 582275970Scy.Ic requestkey 583275970Scycommand selects the key used as the password for the 584275970Scy.Xr ntpdc 1ntpdcmdoc 585275970Scyutility, while the 586275970Scy.Ic controlkey 587275970Scycommand selects the key used as the password for the 588275970Scy.Xr ntpq 1ntpqmdoc 589275970Scyutility. 590275970Scy.Ss Public Key Cryptography 591275970ScyNTPv4 supports the original NTPv3 symmetric key scheme 592275970Scydescribed in RFC-1305 and in addition the Autokey protocol, 593275970Scywhich is based on public key cryptography. 594275970ScyThe Autokey Version 2 protocol described on the Autokey Protocol 595275970Scypage verifies packet integrity using MD5 message digests 596275970Scyand verifies the source with digital signatures and any of several 597275970Scydigest/signature schemes. 598275970ScyOptional identity schemes described on the Identity Schemes 599275970Scypage and based on cryptographic challenge/response algorithms 600275970Scyare also available. 601275970ScyUsing all of these schemes provides strong security against 602275970Scyreplay with or without modification, spoofing, masquerade 603275970Scyand most forms of clogging attacks. 604275970Scy.\" .Pp 605275970Scy.\" The cryptographic means necessary for all Autokey operations 606275970Scy.\" is provided by the OpenSSL software library. 607275970Scy.\" This library is available from http://www.openssl.org/ 608275970Scy.\" and can be installed using the procedures outlined 609275970Scy.\" in the Building and Installing the Distribution page. 610275970Scy.\" Once installed, 611275970Scy.\" the configure and build 612275970Scy.\" process automatically detects the library and links 613275970Scy.\" the library routines required. 614275970Scy.Pp 615275970ScyThe Autokey protocol has several modes of operation 616275970Scycorresponding to the various NTP modes supported. 617275970ScyMost modes use a special cookie which can be 618275970Scycomputed independently by the client and server, 619275970Scybut encrypted in transmission. 620275970ScyAll modes use in addition a variant of the S-KEY scheme, 621275970Scyin which a pseudo-random key list is generated and used 622275970Scyin reverse order. 623275970ScyThese schemes are described along with an executive summary, 624275970Scycurrent status, briefing slides and reading list on the 625275970Scy.Sx Autonomous Authentication 626275970Scypage. 627275970Scy.Pp 628275970ScyThe specific cryptographic environment used by Autokey servers 629275970Scyand clients is determined by a set of files 630275970Scyand soft links generated by the 631275970Scy.Xr ntp-keygen 1ntpkeygenmdoc 632275970Scyprogram. 633275970ScyThis includes a required host key file, 634275970Scyrequired certificate file and optional sign key file, 635275970Scyleapsecond file and identity scheme files. 636275970ScyThe 637275970Scydigest/signature scheme is specified in the X.509 certificate 638275970Scyalong with the matching sign key. 639275970ScyThere are several schemes 640275970Scyavailable in the OpenSSL software library, each identified 641275970Scyby a specific string such as 642275970Scy.Cm md5WithRSAEncryption , 643275970Scywhich stands for the MD5 message digest with RSA 644275970Scyencryption scheme. 645275970ScyThe current NTP distribution supports 646275970Scyall the schemes in the OpenSSL library, including 647275970Scythose based on RSA and DSA digital signatures. 648275970Scy.Pp 649275970ScyNTP secure groups can be used to define cryptographic compartments 650275970Scyand security hierarchies. 651275970ScyIt is important that every host 652275970Scyin the group be able to construct a certificate trail to one 653275970Scyor more trusted hosts in the same group. 654275970ScyEach group 655275970Scyhost runs the Autokey protocol to obtain the certificates 656275970Scyfor all hosts along the trail to one or more trusted hosts. 657275970ScyThis requires the configuration file in all hosts to be 658275970Scyengineered so that, even under anticipated failure conditions, 659275970Scythe NTP subnet will form such that every group host can find 660275970Scya trail to at least one trusted host. 661275970Scy.Ss Naming and Addressing 662275970ScyIt is important to note that Autokey does not use DNS to 663275970Scyresolve addresses, since DNS can't be completely trusted 664275970Scyuntil the name servers have synchronized clocks. 665275970ScyThe cryptographic name used by Autokey to bind the host identity 666275970Scycredentials and cryptographic values must be independent 667275970Scyof interface, network and any other naming convention. 668275970ScyThe name appears in the host certificate in either or both 669275970Scythe subject and issuer fields, so protection against 670275970ScyDNS compromise is essential. 671275970Scy.Pp 672275970ScyBy convention, the name of an Autokey host is the name returned 673275970Scyby the Unix 674275970Scy.Xr gethostname 2 675275970Scysystem call or equivalent in other systems. 676275970ScyBy the system design 677275970Scymodel, there are no provisions to allow alternate names or aliases. 678275970ScyHowever, this is not to say that DNS aliases, different names 679275970Scyfor each interface, etc., are constrained in any way. 680275970Scy.Pp 681275970ScyIt is also important to note that Autokey verifies authenticity 682275970Scyusing the host name, network address and public keys, 683275970Scyall of which are bound together by the protocol specifically 684275970Scyto deflect masquerade attacks. 685275970ScyFor this reason Autokey 686275970Scyincludes the source and destinatino IP addresses in message digest 687275970Scycomputations and so the same addresses must be available 688275970Scyat both the server and client. 689275970ScyFor this reason operation 690275970Scywith network address translation schemes is not possible. 691275970ScyThis reflects the intended robust security model where government 692275970Scyand corporate NTP servers are operated outside firewall perimeters. 693275970Scy.Ss Operation 694275970ScyA specific combination of authentication scheme (none, 695275970Scysymmetric key, public key) and identity scheme is called 696275970Scya cryptotype, although not all combinations are compatible. 697275970ScyThere may be management configurations where the clients, 698275970Scyservers and peers may not all support the same cryptotypes. 699275970ScyA secure NTPv4 subnet can be configured in many ways while 700275970Scykeeping in mind the principles explained above and 701275970Scyin this section. 702275970ScyNote however that some cryptotype 703275970Scycombinations may successfully interoperate with each other, 704275970Scybut may not represent good security practice. 705275970Scy.Pp 706275970ScyThe cryptotype of an association is determined at the time 707275970Scyof mobilization, either at configuration time or some time 708275970Scylater when a message of appropriate cryptotype arrives. 709275970ScyWhen mobilized by a 710275970Scy.Ic server 711275970Scyor 712275970Scy.Ic peer 713275970Scyconfiguration command and no 714275970Scy.Ic key 715275970Scyor 716275970Scy.Ic autokey 717275970Scysubcommands are present, the association is not 718275970Scyauthenticated; if the 719275970Scy.Ic key 720275970Scysubcommand is present, the association is authenticated 721275970Scyusing the symmetric key ID specified; if the 722275970Scy.Ic autokey 723275970Scysubcommand is present, the association is authenticated 724275970Scyusing Autokey. 725275970Scy.Pp 726275970ScyWhen multiple identity schemes are supported in the Autokey 727275970Scyprotocol, the first message exchange determines which one is used. 728275970ScyThe client request message contains bits corresponding 729275970Scyto which schemes it has available. 730275970ScyThe server response message 731275970Scycontains bits corresponding to which schemes it has available. 732275970ScyBoth server and client match the received bits with their own 733275970Scyand select a common scheme. 734275970Scy.Pp 735275970ScyFollowing the principle that time is a public value, 736275970Scya server responds to any client packet that matches 737275970Scyits cryptotype capabilities. 738275970ScyThus, a server receiving 739275970Scyan unauthenticated packet will respond with an unauthenticated 740275970Scypacket, while the same server receiving a packet of a cryptotype 741275970Scyit supports will respond with packets of that cryptotype. 742275970ScyHowever, unconfigured broadcast or manycast client 743275970Scyassociations or symmetric passive associations will not be 744275970Scymobilized unless the server supports a cryptotype compatible 745275970Scywith the first packet received. 746275970ScyBy default, unauthenticated associations will not be mobilized 747275970Scyunless overridden in a decidedly dangerous way. 748275970Scy.Pp 749275970ScySome examples may help to reduce confusion. 750275970ScyClient Alice has no specific cryptotype selected. 751275970ScyServer Bob has both a symmetric key file and minimal Autokey files. 752275970ScyAlice's unauthenticated messages arrive at Bob, who replies with 753275970Scyunauthenticated messages. 754275970ScyCathy has a copy of Bob's symmetric 755275970Scykey file and has selected key ID 4 in messages to Bob. 756275970ScyBob verifies the message with his key ID 4. 757275970ScyIf it's the 758275970Scysame key and the message is verified, Bob sends Cathy a reply 759275970Scyauthenticated with that key. 760275970ScyIf verification fails, 761275970ScyBob sends Cathy a thing called a crypto-NAK, which tells her 762275970Scysomething broke. 763275970ScyShe can see the evidence using the 764275970Scy.Xr ntpq 1ntpqmdoc 765275970Scyprogram. 766275970Scy.Pp 767275970ScyDenise has rolled her own host key and certificate. 768275970ScyShe also uses one of the identity schemes as Bob. 769275970ScyShe sends the first Autokey message to Bob and they 770275970Scyboth dance the protocol authentication and identity steps. 771275970ScyIf all comes out okay, Denise and Bob continue as described above. 772275970Scy.Pp 773275970ScyIt should be clear from the above that Bob can support 774275970Scyall the girls at the same time, as long as he has compatible 775275970Scyauthentication and identity credentials. 776275970ScyNow, Bob can act just like the girls in his own choice of servers; 777275970Scyhe can run multiple configured associations with multiple different 778275970Scyservers (or the same server, although that might not be useful). 779275970ScyBut, wise security policy might preclude some cryptotype 780275970Scycombinations; for instance, running an identity scheme 781275970Scywith one server and no authentication with another might not be wise. 782275970Scy.Ss Key Management 783275970ScyThe cryptographic values used by the Autokey protocol are 784275970Scyincorporated as a set of files generated by the 785275970Scy.Xr ntp-keygen 1ntpkeygenmdoc 786275970Scyutility program, including symmetric key, host key and 787275970Scypublic certificate files, as well as sign key, identity parameters 788275970Scyand leapseconds files. 789275970ScyAlternatively, host and sign keys and 790275970Scycertificate files can be generated by the OpenSSL utilities 791275970Scyand certificates can be imported from public certificate 792275970Scyauthorities. 793275970ScyNote that symmetric keys are necessary for the 794275970Scy.Xr ntpq 1ntpqmdoc 795275970Scyand 796275970Scy.Xr ntpdc 1ntpdcmdoc 797275970Scyutility programs. 798275970ScyThe remaining files are necessary only for the 799275970ScyAutokey protocol. 800275970Scy.Pp 801275970ScyCertificates imported from OpenSSL or public certificate 802275970Scyauthorities have certian limitations. 803275970ScyThe certificate should be in ASN.1 syntax, X.509 Version 3 804275970Scyformat and encoded in PEM, which is the same format 805275970Scyused by OpenSSL. 806275970ScyThe overall length of the certificate encoded 807275970Scyin ASN.1 must not exceed 1024 bytes. 808275970ScyThe subject distinguished 809275970Scyname field (CN) is the fully qualified name of the host 810275970Scyon which it is used; the remaining subject fields are ignored. 811275970ScyThe certificate extension fields must not contain either 812275970Scya subject key identifier or a issuer key identifier field; 813275970Scyhowever, an extended key usage field for a trusted host must 814275970Scycontain the value 815275970Scy.Cm trustRoot ; . 816275970ScyOther extension fields are ignored. 817275970Scy.Ss Authentication Commands 818275970Scy.Bl -tag -width indent 819275970Scy.It Ic autokey Op Ar logsec 820275970ScySpecifies the interval between regenerations of the session key 821275970Scylist used with the Autokey protocol. 822275970ScyNote that the size of the key 823275970Scylist for each association depends on this interval and the current 824275970Scypoll interval. 825275970ScyThe default value is 12 (4096 s or about 1.1 hours). 826275970ScyFor poll intervals above the specified interval, a session key list 827275970Scywith a single entry will be regenerated for every message 828275970Scysent. 829275970Scy.It Ic controlkey Ar key 830275970ScySpecifies the key identifier to use with the 831275970Scy.Xr ntpq 1ntpqmdoc 832275970Scyutility, which uses the standard 833275970Scyprotocol defined in RFC-1305. 834275970ScyThe 835275970Scy.Ar key 836275970Scyargument is 837275970Scythe key identifier for a trusted key, where the value can be in the 838275970Scyrange 1 to 65,534, inclusive. 839275970Scy.It Xo Ic crypto 840275970Scy.Op Cm cert Ar file 841275970Scy.Op Cm leap Ar file 842275970Scy.Op Cm randfile Ar file 843275970Scy.Op Cm host Ar file 844275970Scy.Op Cm sign Ar file 845275970Scy.Op Cm gq Ar file 846275970Scy.Op Cm gqpar Ar file 847275970Scy.Op Cm iffpar Ar file 848275970Scy.Op Cm mvpar Ar file 849275970Scy.Op Cm pw Ar password 850275970Scy.Xc 851275970ScyThis command requires the OpenSSL library. 852275970ScyIt activates public key 853275970Scycryptography, selects the message digest and signature 854275970Scyencryption scheme and loads the required private and public 855275970Scyvalues described above. 856275970ScyIf one or more files are left unspecified, 857275970Scythe default names are used as described above. 858275970ScyUnless the complete path and name of the file are specified, the 859275970Scylocation of a file is relative to the keys directory specified 860275970Scyin the 861275970Scy.Ic keysdir 862275970Scycommand or default 863275970Scy.Pa /usr/local/etc . 864275970ScyFollowing are the subcommands: 865275970Scy.Bl -tag -width indent 866275970Scy.It Cm cert Ar file 867275970ScySpecifies the location of the required host public certificate file. 868275970ScyThis overrides the link 869275970Scy.Pa ntpkey_cert_ Ns Ar hostname 870275970Scyin the keys directory. 871275970Scy.It Cm gqpar Ar file 872275970ScySpecifies the location of the optional GQ parameters file. 873275970ScyThis 874275970Scyoverrides the link 875275970Scy.Pa ntpkey_gq_ Ns Ar hostname 876275970Scyin the keys directory. 877275970Scy.It Cm host Ar file 878275970ScySpecifies the location of the required host key file. 879275970ScyThis overrides 880275970Scythe link 881275970Scy.Pa ntpkey_key_ Ns Ar hostname 882275970Scyin the keys directory. 883275970Scy.It Cm iffpar Ar file 884275970ScySpecifies the location of the optional IFF parameters file.This 885275970Scyoverrides the link 886275970Scy.Pa ntpkey_iff_ Ns Ar hostname 887275970Scyin the keys directory. 888275970Scy.It Cm leap Ar file 889275970ScySpecifies the location of the optional leapsecond file. 890275970ScyThis overrides the link 891275970Scy.Pa ntpkey_leap 892275970Scyin the keys directory. 893275970Scy.It Cm mvpar Ar file 894275970ScySpecifies the location of the optional MV parameters file. 895275970ScyThis 896275970Scyoverrides the link 897275970Scy.Pa ntpkey_mv_ Ns Ar hostname 898275970Scyin the keys directory. 899275970Scy.It Cm pw Ar password 900275970ScySpecifies the password to decrypt files containing private keys and 901275970Scyidentity parameters. 902275970ScyThis is required only if these files have been 903275970Scyencrypted. 904275970Scy.It Cm randfile Ar file 905275970ScySpecifies the location of the random seed file used by the OpenSSL 906275970Scylibrary. 907275970ScyThe defaults are described in the main text above. 908275970Scy.It Cm sign Ar file 909275970ScySpecifies the location of the optional sign key file. 910275970ScyThis overrides 911275970Scythe link 912275970Scy.Pa ntpkey_sign_ Ns Ar hostname 913275970Scyin the keys directory. 914275970ScyIf this file is 915275970Scynot found, the host key is also the sign key. 916275970Scy.El 917275970Scy.It Ic keys Ar keyfile 918275970ScySpecifies the complete path and location of the MD5 key file 919275970Scycontaining the keys and key identifiers used by 920275970Scy.Xr ntpd 1ntpdmdoc , 921275970Scy.Xr ntpq 1ntpqmdoc 922275970Scyand 923275970Scy.Xr ntpdc 1ntpdcmdoc 924275970Scywhen operating with symmetric key cryptography. 925275970ScyThis is the same operation as the 926275970Scy.Fl k 927275970Scycommand line option. 928275970Scy.It Ic keysdir Ar path 929275970ScyThis command specifies the default directory path for 930275970Scycryptographic keys, parameters and certificates. 931275970ScyThe default is 932275970Scy.Pa /usr/local/etc/ . 933275970Scy.It Ic requestkey Ar key 934275970ScySpecifies the key identifier to use with the 935275970Scy.Xr ntpdc 1ntpdcmdoc 936275970Scyutility program, which uses a 937275970Scyproprietary protocol specific to this implementation of 938275970Scy.Xr ntpd 1ntpdmdoc . 939275970ScyThe 940275970Scy.Ar key 941275970Scyargument is a key identifier 942275970Scyfor the trusted key, where the value can be in the range 1 to 943275970Scy65,534, inclusive. 944275970Scy.It Ic revoke Ar logsec 945275970ScySpecifies the interval between re-randomization of certain 946275970Scycryptographic values used by the Autokey scheme, as a power of 2 in 947275970Scyseconds. 948275970ScyThese values need to be updated frequently in order to 949275970Scydeflect brute-force attacks on the algorithms of the scheme; 950275970Scyhowever, updating some values is a relatively expensive operation. 951275970ScyThe default interval is 16 (65,536 s or about 18 hours). 952275970ScyFor poll 953275970Scyintervals above the specified interval, the values will be updated 954275970Scyfor every message sent. 955275970Scy.It Ic trustedkey Ar key ... 956275970ScySpecifies the key identifiers which are trusted for the 957275970Scypurposes of authenticating peers with symmetric key cryptography, 958275970Scyas well as keys used by the 959275970Scy.Xr ntpq 1ntpqmdoc 960275970Scyand 961275970Scy.Xr ntpdc 1ntpdcmdoc 962275970Scyprograms. 963275970ScyThe authentication procedures require that both the local 964275970Scyand remote servers share the same key and key identifier for this 965275970Scypurpose, although different keys can be used with different 966275970Scyservers. 967275970ScyThe 968275970Scy.Ar key 969275970Scyarguments are 32-bit unsigned 970275970Scyintegers with values from 1 to 65,534. 971275970Scy.El 972275970Scy.Ss Error Codes 973275970ScyThe following error codes are reported via the NTP control 974275970Scyand monitoring protocol trap mechanism. 975275970Scy.Bl -tag -width indent 976275970Scy.It 101 977275970Scy.Pq bad field format or length 978275970ScyThe packet has invalid version, length or format. 979275970Scy.It 102 980275970Scy.Pq bad timestamp 981275970ScyThe packet timestamp is the same or older than the most recent received. 982275970ScyThis could be due to a replay or a server clock time step. 983275970Scy.It 103 984275970Scy.Pq bad filestamp 985275970ScyThe packet filestamp is the same or older than the most recent received. 986275970ScyThis could be due to a replay or a key file generation error. 987275970Scy.It 104 988275970Scy.Pq bad or missing public key 989275970ScyThe public key is missing, has incorrect format or is an unsupported type. 990275970Scy.It 105 991275970Scy.Pq unsupported digest type 992275970ScyThe server requires an unsupported digest/signature scheme. 993275970Scy.It 106 994275970Scy.Pq mismatched digest types 995275970ScyNot used. 996275970Scy.It 107 997275970Scy.Pq bad signature length 998275970ScyThe signature length does not match the current public key. 999275970Scy.It 108 1000275970Scy.Pq signature not verified 1001275970ScyThe message fails the signature check. 1002275970ScyIt could be bogus or signed by a 1003275970Scydifferent private key. 1004275970Scy.It 109 1005275970Scy.Pq certificate not verified 1006275970ScyThe certificate is invalid or signed with the wrong key. 1007275970Scy.It 110 1008275970Scy.Pq certificate not verified 1009275970ScyThe certificate is not yet valid or has expired or the signature could not 1010275970Scybe verified. 1011275970Scy.It 111 1012275970Scy.Pq bad or missing cookie 1013275970ScyThe cookie is missing, corrupted or bogus. 1014275970Scy.It 112 1015275970Scy.Pq bad or missing leapseconds table 1016275970ScyThe leapseconds table is missing, corrupted or bogus. 1017275970Scy.It 113 1018275970Scy.Pq bad or missing certificate 1019275970ScyThe certificate is missing, corrupted or bogus. 1020275970Scy.It 114 1021275970Scy.Pq bad or missing identity 1022275970ScyThe identity key is missing, corrupt or bogus. 1023275970Scy.El 1024275970Scy.Sh Monitoring Support 1025275970Scy.Xr ntpd 1ntpdmdoc 1026275970Scyincludes a comprehensive monitoring facility suitable 1027275970Scyfor continuous, long term recording of server and client 1028275970Scytimekeeping performance. 1029275970ScySee the 1030275970Scy.Ic statistics 1031275970Scycommand below 1032275970Scyfor a listing and example of each type of statistics currently 1033275970Scysupported. 1034275970ScyStatistic files are managed using file generation sets 1035275970Scyand scripts in the 1036275970Scy.Pa ./scripts 1037275970Scydirectory of this distribution. 1038275970ScyUsing 1039275970Scythese facilities and 1040275970Scy.Ux 1041275970Scy.Xr cron 8 1042275970Scyjobs, the data can be 1043275970Scyautomatically summarized and archived for retrospective analysis. 1044275970Scy.Ss Monitoring Commands 1045275970Scy.Bl -tag -width indent 1046275970Scy.It Ic statistics Ar name ... 1047275970ScyEnables writing of statistics records. 1048275970ScyCurrently, eight kinds of 1049275970Scy.Ar name 1050275970Scystatistics are supported. 1051275970Scy.Bl -tag -width indent 1052275970Scy.It Cm clockstats 1053275970ScyEnables recording of clock driver statistics information. 1054275970ScyEach update 1055275970Scyreceived from a clock driver appends a line of the following form to 1056275970Scythe file generation set named 1057275970Scy.Cm clockstats : 1058275970Scy.Bd -literal 1059275970Scy49213 525.624 127.127.4.1 93 226 00:08:29.606 D 1060275970Scy.Ed 1061275970Scy.Pp 1062275970ScyThe first two fields show the date (Modified Julian Day) and time 1063275970Scy(seconds and fraction past UTC midnight). 1064275970ScyThe next field shows the 1065275970Scyclock address in dotted-quad notation. 1066275970ScyThe final field shows the last 1067275970Scytimecode received from the clock in decoded ASCII format, where 1068275970Scymeaningful. 1069275970ScyIn some clock drivers a good deal of additional information 1070275970Scycan be gathered and displayed as well. 1071275970ScySee information specific to each 1072275970Scyclock for further details. 1073275970Scy.It Cm cryptostats 1074275970ScyThis option requires the OpenSSL cryptographic software library. 1075275970ScyIt 1076275970Scyenables recording of cryptographic public key protocol information. 1077275970ScyEach message received by the protocol module appends a line of the 1078275970Scyfollowing form to the file generation set named 1079275970Scy.Cm cryptostats : 1080275970Scy.Bd -literal 1081275970Scy49213 525.624 127.127.4.1 message 1082275970Scy.Ed 1083275970Scy.Pp 1084275970ScyThe first two fields show the date (Modified Julian Day) and time 1085275970Scy(seconds and fraction past UTC midnight). 1086275970ScyThe next field shows the peer 1087275970Scyaddress in dotted-quad notation, The final message field includes the 1088275970Scymessage type and certain ancillary information. 1089275970ScySee the 1090275970Scy.Sx Authentication Options 1091275970Scysection for further information. 1092275970Scy.It Cm loopstats 1093275970ScyEnables recording of loop filter statistics information. 1094275970ScyEach 1095275970Scyupdate of the local clock outputs a line of the following form to 1096275970Scythe file generation set named 1097275970Scy.Cm loopstats : 1098275970Scy.Bd -literal 1099275970Scy50935 75440.031 0.000006019 13.778190 0.000351733 0.0133806 1100275970Scy.Ed 1101275970Scy.Pp 1102275970ScyThe first two fields show the date (Modified Julian Day) and 1103275970Scytime (seconds and fraction past UTC midnight). 1104275970ScyThe next five fields 1105275970Scyshow time offset (seconds), frequency offset (parts per million - 1106275970ScyPPM), RMS jitter (seconds), Allan deviation (PPM) and clock 1107275970Scydiscipline time constant. 1108275970Scy.It Cm peerstats 1109275970ScyEnables recording of peer statistics information. 1110275970ScyThis includes 1111275970Scystatistics records of all peers of a NTP server and of special 1112275970Scysignals, where present and configured. 1113275970ScyEach valid update appends a 1114275970Scyline of the following form to the current element of a file 1115275970Scygeneration set named 1116275970Scy.Cm peerstats : 1117275970Scy.Bd -literal 1118275970Scy48773 10847.650 127.127.4.1 9714 -0.001605376 0.000000000 0.001424877 0.000958674 1119275970Scy.Ed 1120275970Scy.Pp 1121275970ScyThe first two fields show the date (Modified Julian Day) and 1122275970Scytime (seconds and fraction past UTC midnight). 1123275970ScyThe next two fields 1124275970Scyshow the peer address in dotted-quad notation and status, 1125275970Scyrespectively. 1126275970ScyThe status field is encoded in hex in the format 1127275970Scydescribed in Appendix A of the NTP specification RFC 1305. 1128275970ScyThe final four fields show the offset, 1129275970Scydelay, dispersion and RMS jitter, all in seconds. 1130275970Scy.It Cm rawstats 1131275970ScyEnables recording of raw-timestamp statistics information. 1132275970ScyThis 1133275970Scyincludes statistics records of all peers of a NTP server and of 1134275970Scyspecial signals, where present and configured. 1135275970ScyEach NTP message 1136275970Scyreceived from a peer or clock driver appends a line of the 1137275970Scyfollowing form to the file generation set named 1138275970Scy.Cm rawstats : 1139275970Scy.Bd -literal 1140275970Scy50928 2132.543 128.4.1.1 128.4.1.20 3102453281.584327000 3102453281.58622800031 02453332.540806000 3102453332.541458000 1141275970Scy.Ed 1142275970Scy.Pp 1143275970ScyThe first two fields show the date (Modified Julian Day) and 1144275970Scytime (seconds and fraction past UTC midnight). 1145275970ScyThe next two fields 1146275970Scyshow the remote peer or clock address followed by the local address 1147275970Scyin dotted-quad notation. 1148275970ScyThe final four fields show the originate, 1149275970Scyreceive, transmit and final NTP timestamps in order. 1150275970ScyThe timestamp 1151275970Scyvalues are as received and before processing by the various data 1152275970Scysmoothing and mitigation algorithms. 1153275970Scy.It Cm sysstats 1154275970ScyEnables recording of ntpd statistics counters on a periodic basis. 1155275970ScyEach 1156275970Scyhour a line of the following form is appended to the file generation 1157275970Scyset named 1158275970Scy.Cm sysstats : 1159275970Scy.Bd -literal 1160275970Scy50928 2132.543 36000 81965 0 9546 56 71793 512 540 10 147 1161275970Scy.Ed 1162275970Scy.Pp 1163275970ScyThe first two fields show the date (Modified Julian Day) and time 1164275970Scy(seconds and fraction past UTC midnight). 1165275970ScyThe remaining ten fields show 1166275970Scythe statistics counter values accumulated since the last generated 1167275970Scyline. 1168275970Scy.Bl -tag -width indent 1169275970Scy.It Time since restart Cm 36000 1170275970ScyTime in hours since the system was last rebooted. 1171275970Scy.It Packets received Cm 81965 1172275970ScyTotal number of packets received. 1173275970Scy.It Packets processed Cm 0 1174275970ScyNumber of packets received in response to previous packets sent 1175275970Scy.It Current version Cm 9546 1176275970ScyNumber of packets matching the current NTP version. 1177275970Scy.It Previous version Cm 56 1178275970ScyNumber of packets matching the previous NTP version. 1179275970Scy.It Bad version Cm 71793 1180275970ScyNumber of packets matching neither NTP version. 1181275970Scy.It Access denied Cm 512 1182275970ScyNumber of packets denied access for any reason. 1183275970Scy.It Bad length or format Cm 540 1184275970ScyNumber of packets with invalid length, format or port number. 1185275970Scy.It Bad authentication Cm 10 1186275970ScyNumber of packets not verified as authentic. 1187275970Scy.It Rate exceeded Cm 147 1188275970ScyNumber of packets discarded due to rate limitation. 1189275970Scy.El 1190275970Scy.It Cm statsdir Ar directory_path 1191275970ScyIndicates the full path of a directory where statistics files 1192275970Scyshould be created (see below). 1193275970ScyThis keyword allows 1194275970Scythe (otherwise constant) 1195275970Scy.Cm filegen 1196275970Scyfilename prefix to be modified for file generation sets, which 1197275970Scyis useful for handling statistics logs. 1198275970Scy.It Cm filegen Ar name Xo 1199275970Scy.Op Cm file Ar filename 1200275970Scy.Op Cm type Ar typename 1201275970Scy.Op Cm link | nolink 1202275970Scy.Op Cm enable | disable 1203275970Scy.Xc 1204275970ScyConfigures setting of generation file set name. 1205275970ScyGeneration 1206275970Scyfile sets provide a means for handling files that are 1207275970Scycontinuously growing during the lifetime of a server. 1208275970ScyServer statistics are a typical example for such files. 1209275970ScyGeneration file sets provide access to a set of files used 1210275970Scyto store the actual data. 1211275970ScyAt any time at most one element 1212275970Scyof the set is being written to. 1213275970ScyThe type given specifies 1214275970Scywhen and how data will be directed to a new element of the set. 1215275970ScyThis way, information stored in elements of a file set 1216275970Scythat are currently unused are available for administrational 1217275970Scyoperations without the risk of disturbing the operation of ntpd. 1218275970Scy(Most important: they can be removed to free space for new data 1219275970Scyproduced.) 1220275970Scy.Pp 1221275970ScyNote that this command can be sent from the 1222275970Scy.Xr ntpdc 1ntpdcmdoc 1223275970Scyprogram running at a remote location. 1224275970Scy.Bl -tag -width indent 1225275970Scy.It Cm name 1226275970ScyThis is the type of the statistics records, as shown in the 1227275970Scy.Cm statistics 1228275970Scycommand. 1229275970Scy.It Cm file Ar filename 1230275970ScyThis is the file name for the statistics records. 1231275970ScyFilenames of set 1232275970Scymembers are built from three concatenated elements 1233275970Scy.Ar Cm prefix , 1234275970Scy.Ar Cm filename 1235275970Scyand 1236275970Scy.Ar Cm suffix : 1237275970Scy.Bl -tag -width indent 1238275970Scy.It Cm prefix 1239275970ScyThis is a constant filename path. 1240275970ScyIt is not subject to 1241275970Scymodifications via the 1242275970Scy.Ar filegen 1243275970Scyoption. 1244275970ScyIt is defined by the 1245275970Scyserver, usually specified as a compile-time constant. 1246275970ScyIt may, 1247275970Scyhowever, be configurable for individual file generation sets 1248275970Scyvia other commands. 1249275970ScyFor example, the prefix used with 1250275970Scy.Ar loopstats 1251275970Scyand 1252275970Scy.Ar peerstats 1253275970Scygeneration can be configured using the 1254275970Scy.Ar statsdir 1255275970Scyoption explained above. 1256275970Scy.It Cm filename 1257275970ScyThis string is directly concatenated to the prefix mentioned 1258275970Scyabove (no intervening 1259275970Scy.Ql / ) . 1260275970ScyThis can be modified using 1261275970Scythe file argument to the 1262275970Scy.Ar filegen 1263275970Scystatement. 1264275970ScyNo 1265275970Scy.Pa .. 1266275970Scyelements are 1267275970Scyallowed in this component to prevent filenames referring to 1268275970Scyparts outside the filesystem hierarchy denoted by 1269275970Scy.Ar prefix . 1270275970Scy.It Cm suffix 1271275970ScyThis part is reflects individual elements of a file set. 1272275970ScyIt is 1273275970Scygenerated according to the type of a file set. 1274275970Scy.El 1275275970Scy.It Cm type Ar typename 1276275970ScyA file generation set is characterized by its type. 1277275970ScyThe following 1278275970Scytypes are supported: 1279275970Scy.Bl -tag -width indent 1280275970Scy.It Cm none 1281275970ScyThe file set is actually a single plain file. 1282275970Scy.It Cm pid 1283275970ScyOne element of file set is used per incarnation of a ntpd 1284275970Scyserver. 1285275970ScyThis type does not perform any changes to file set 1286275970Scymembers during runtime, however it provides an easy way of 1287275970Scyseparating files belonging to different 1288275970Scy.Xr ntpd 1ntpdmdoc 1289275970Scyserver incarnations. 1290275970ScyThe set member filename is built by appending a 1291275970Scy.Ql \&. 1292275970Scyto concatenated 1293275970Scy.Ar prefix 1294275970Scyand 1295275970Scy.Ar filename 1296275970Scystrings, and 1297275970Scyappending the decimal representation of the process ID of the 1298275970Scy.Xr ntpd 1ntpdmdoc 1299275970Scyserver process. 1300275970Scy.It Cm day 1301275970ScyOne file generation set element is created per day. 1302275970ScyA day is 1303275970Scydefined as the period between 00:00 and 24:00 UTC. 1304275970ScyThe file set 1305275970Scymember suffix consists of a 1306275970Scy.Ql \&. 1307275970Scyand a day specification in 1308275970Scythe form 1309275970Scy.Cm YYYYMMdd . 1310275970Scy.Cm YYYY 1311275970Scyis a 4-digit year number (e.g., 1992). 1312275970Scy.Cm MM 1313275970Scyis a two digit month number. 1314275970Scy.Cm dd 1315275970Scyis a two digit day number. 1316275970ScyThus, all information written at 10 December 1992 would end up 1317275970Scyin a file named 1318275970Scy.Ar prefix 1319275970Scy.Ar filename Ns .19921210 . 1320275970Scy.It Cm week 1321275970ScyAny file set member contains data related to a certain week of 1322275970Scya year. 1323275970ScyThe term week is defined by computing day-of-year 1324275970Scymodulo 7. 1325275970ScyElements of such a file generation set are 1326275970Scydistinguished by appending the following suffix to the file set 1327275970Scyfilename base: A dot, a 4-digit year number, the letter 1328275970Scy.Cm W , 1329275970Scyand a 2-digit week number. 1330275970ScyFor example, information from January, 1331275970Scy10th 1992 would end up in a file with suffix 1332275970Scy.No . Ns Ar 1992W1 . 1333275970Scy.It Cm month 1334275970ScyOne generation file set element is generated per month. 1335275970ScyThe 1336275970Scyfile name suffix consists of a dot, a 4-digit year number, and 1337275970Scya 2-digit month. 1338275970Scy.It Cm year 1339275970ScyOne generation file element is generated per year. 1340275970ScyThe filename 1341275970Scysuffix consists of a dot and a 4 digit year number. 1342275970Scy.It Cm age 1343275970ScyThis type of file generation sets changes to a new element of 1344275970Scythe file set every 24 hours of server operation. 1345275970ScyThe filename 1346275970Scysuffix consists of a dot, the letter 1347275970Scy.Cm a , 1348275970Scyand an 8-digit number. 1349275970ScyThis number is taken to be the number of seconds the server is 1350275970Scyrunning at the start of the corresponding 24-hour period. 1351275970ScyInformation is only written to a file generation by specifying 1352275970Scy.Cm enable ; 1353275970Scyoutput is prevented by specifying 1354275970Scy.Cm disable . 1355275970Scy.El 1356275970Scy.It Cm link | nolink 1357275970ScyIt is convenient to be able to access the current element of a file 1358275970Scygeneration set by a fixed name. 1359275970ScyThis feature is enabled by 1360275970Scyspecifying 1361275970Scy.Cm link 1362275970Scyand disabled using 1363275970Scy.Cm nolink . 1364275970ScyIf link is specified, a 1365275970Scyhard link from the current file set element to a file without 1366275970Scysuffix is created. 1367275970ScyWhen there is already a file with this name and 1368275970Scythe number of links of this file is one, it is renamed appending a 1369275970Scydot, the letter 1370275970Scy.Cm C , 1371275970Scyand the pid of the ntpd server process. 1372275970ScyWhen the 1373275970Scynumber of links is greater than one, the file is unlinked. 1374275970ScyThis 1375275970Scyallows the current file to be accessed by a constant name. 1376275970Scy.It Cm enable \&| Cm disable 1377275970ScyEnables or disables the recording function. 1378275970Scy.El 1379275970Scy.El 1380275970Scy.El 1381275970Scy.Sh Access Control Support 1382275970ScyThe 1383275970Scy.Xr ntpd 1ntpdmdoc 1384275970Scydaemon implements a general purpose address/mask based restriction 1385275970Scylist. 1386275970ScyThe list contains address/match entries sorted first 1387275970Scyby increasing address values and and then by increasing mask values. 1388275970ScyA match occurs when the bitwise AND of the mask and the packet 1389275970Scysource address is equal to the bitwise AND of the mask and 1390275970Scyaddress in the list. 1391275970ScyThe list is searched in order with the 1392275970Scylast match found defining the restriction flags associated 1393275970Scywith the entry. 1394275970ScyAdditional information and examples can be found in the 1395275970Scy.Qq Notes on Configuring NTP and Setting up a NTP Subnet 1396275970Scypage 1397275970Scy(available as part of the HTML documentation 1398275970Scyprovided in 1399275970Scy.Pa /usr/share/doc/ntp ) . 1400275970Scy.Pp 1401275970ScyThe restriction facility was implemented in conformance 1402275970Scywith the access policies for the original NSFnet backbone 1403275970Scytime servers. 1404275970ScyLater the facility was expanded to deflect 1405275970Scycryptographic and clogging attacks. 1406275970ScyWhile this facility may 1407275970Scybe useful for keeping unwanted or broken or malicious clients 1408275970Scyfrom congesting innocent servers, it should not be considered 1409275970Scyan alternative to the NTP authentication facilities. 1410275970ScySource address based restrictions are easily circumvented 1411275970Scyby a determined cracker. 1412275970Scy.Pp 1413275970ScyClients can be denied service because they are explicitly 1414275970Scyincluded in the restrict list created by the restrict command 1415275970Scyor implicitly as the result of cryptographic or rate limit 1416275970Scyviolations. 1417275970ScyCryptographic violations include certificate 1418275970Scyor identity verification failure; rate limit violations generally 1419275970Scyresult from defective NTP implementations that send packets 1420275970Scyat abusive rates. 1421275970ScySome violations cause denied service 1422275970Scyonly for the offending packet, others cause denied service 1423275970Scyfor a timed period and others cause the denied service for 1424275970Scyan indefinate period. 1425275970ScyWhen a client or network is denied access 1426275970Scyfor an indefinate period, the only way at present to remove 1427275970Scythe restrictions is by restarting the server. 1428275970Scy.Ss The Kiss-of-Death Packet 1429275970ScyOrdinarily, packets denied service are simply dropped with no 1430275970Scyfurther action except incrementing statistics counters. 1431275970ScySometimes a 1432275970Scymore proactive response is needed, such as a server message that 1433275970Scyexplicitly requests the client to stop sending and leave a message 1434275970Scyfor the system operator. 1435275970ScyA special packet format has been created 1436275970Scyfor this purpose called the "kiss-of-death" (KoD) packet. 1437275970ScyKoD packets have the leap bits set unsynchronized and stratum set 1438275970Scyto zero and the reference identifier field set to a four-byte 1439275970ScyASCII code. 1440275970ScyIf the 1441275970Scy.Cm noserve 1442275970Scyor 1443275970Scy.Cm notrust 1444275970Scyflag of the matching restrict list entry is set, 1445275970Scythe code is "DENY"; if the 1446275970Scy.Cm limited 1447275970Scyflag is set and the rate limit 1448275970Scyis exceeded, the code is "RATE". 1449275970ScyFinally, if a cryptographic violation occurs, the code is "CRYP". 1450275970Scy.Pp 1451275970ScyA client receiving a KoD performs a set of sanity checks to 1452275970Scyminimize security exposure, then updates the stratum and 1453275970Scyreference identifier peer variables, sets the access 1454275970Scydenied (TEST4) bit in the peer flash variable and sends 1455275970Scya message to the log. 1456275970ScyAs long as the TEST4 bit is set, 1457275970Scythe client will send no further packets to the server. 1458275970ScyThe only way at present to recover from this condition is 1459275970Scyto restart the protocol at both the client and server. 1460275970ScyThis 1461275970Scyhappens automatically at the client when the association times out. 1462275970ScyIt will happen at the server only if the server operator cooperates. 1463275970Scy.Ss Access Control Commands 1464275970Scy.Bl -tag -width indent 1465275970Scy.It Xo Ic discard 1466275970Scy.Op Cm average Ar avg 1467275970Scy.Op Cm minimum Ar min 1468275970Scy.Op Cm monitor Ar prob 1469275970Scy.Xc 1470275970ScySet the parameters of the 1471275970Scy.Cm limited 1472275970Scyfacility which protects the server from 1473275970Scyclient abuse. 1474275970ScyThe 1475275970Scy.Cm average 1476275970Scysubcommand specifies the minimum average packet 1477275970Scyspacing, while the 1478275970Scy.Cm minimum 1479275970Scysubcommand specifies the minimum packet spacing. 1480275970ScyPackets that violate these minima are discarded 1481275970Scyand a kiss-o'-death packet returned if enabled. 1482275970ScyThe default 1483275970Scyminimum average and minimum are 5 and 2, respectively. 1484275970ScyThe monitor subcommand specifies the probability of discard 1485275970Scyfor packets that overflow the rate-control window. 1486275970Scy.It Xo Ic restrict address 1487275970Scy.Op Cm mask Ar mask 1488275970Scy.Op Ar flag ... 1489275970Scy.Xc 1490275970ScyThe 1491275970Scy.Ar address 1492275970Scyargument expressed in 1493275970Scydotted-quad form is the address of a host or network. 1494275970ScyAlternatively, the 1495275970Scy.Ar address 1496275970Scyargument can be a valid host DNS name. 1497275970ScyThe 1498275970Scy.Ar mask 1499275970Scyargument expressed in dotted-quad form defaults to 1500275970Scy.Cm 255.255.255.255 , 1501275970Scymeaning that the 1502275970Scy.Ar address 1503275970Scyis treated as the address of an individual host. 1504275970ScyA default entry (address 1505275970Scy.Cm 0.0.0.0 , 1506275970Scymask 1507275970Scy.Cm 0.0.0.0 ) 1508275970Scyis always included and is always the first entry in the list. 1509275970ScyNote that text string 1510275970Scy.Cm default , 1511275970Scywith no mask option, may 1512275970Scybe used to indicate the default entry. 1513275970ScyIn the current implementation, 1514275970Scy.Cm flag 1515275970Scyalways 1516275970Scyrestricts access, i.e., an entry with no flags indicates that free 1517275970Scyaccess to the server is to be given. 1518275970ScyThe flags are not orthogonal, 1519275970Scyin that more restrictive flags will often make less restrictive 1520275970Scyones redundant. 1521275970ScyThe flags can generally be classed into two 1522275970Scycategories, those which restrict time service and those which 1523275970Scyrestrict informational queries and attempts to do run-time 1524275970Scyreconfiguration of the server. 1525275970ScyOne or more of the following flags 1526275970Scymay be specified: 1527275970Scy.Bl -tag -width indent 1528275970Scy.It Cm ignore 1529275970ScyDeny packets of all kinds, including 1530275970Scy.Xr ntpq 1ntpqmdoc 1531275970Scyand 1532275970Scy.Xr ntpdc 1ntpdcmdoc 1533275970Scyqueries. 1534275970Scy.It Cm kod 1535275970ScyIf this flag is set when an access violation occurs, a kiss-o'-death 1536275970Scy(KoD) packet is sent. 1537275970ScyKoD packets are rate limited to no more than one 1538275970Scyper second. 1539275970ScyIf another KoD packet occurs within one second after the 1540275970Scylast one, the packet is dropped. 1541275970Scy.It Cm limited 1542275970ScyDeny service if the packet spacing violates the lower limits specified 1543275970Scyin the discard command. 1544275970ScyA history of clients is kept using the 1545275970Scymonitoring capability of 1546275970Scy.Xr ntpd 1ntpdmdoc . 1547275970ScyThus, monitoring is always active as 1548275970Scylong as there is a restriction entry with the 1549275970Scy.Cm limited 1550275970Scyflag. 1551275970Scy.It Cm lowpriotrap 1552275970ScyDeclare traps set by matching hosts to be low priority. 1553275970ScyThe 1554275970Scynumber of traps a server can maintain is limited (the current limit 1555275970Scyis 3). 1556275970ScyTraps are usually assigned on a first come, first served 1557275970Scybasis, with later trap requestors being denied service. 1558275970ScyThis flag 1559275970Scymodifies the assignment algorithm by allowing low priority traps to 1560275970Scybe overridden by later requests for normal priority traps. 1561275970Scy.It Cm nomodify 1562275970ScyDeny 1563275970Scy.Xr ntpq 1ntpqmdoc 1564275970Scyand 1565275970Scy.Xr ntpdc 1ntpdcmdoc 1566275970Scyqueries which attempt to modify the state of the 1567275970Scyserver (i.e., run time reconfiguration). 1568275970ScyQueries which return 1569275970Scyinformation are permitted. 1570275970Scy.It Cm noquery 1571275970ScyDeny 1572275970Scy.Xr ntpq 1ntpqmdoc 1573275970Scyand 1574275970Scy.Xr ntpdc 1ntpdcmdoc 1575275970Scyqueries. 1576275970ScyTime service is not affected. 1577275970Scy.It Cm nopeer 1578275970ScyDeny packets which would result in mobilizing a new association. 1579275970ScyThis 1580275970Scyincludes broadcast and symmetric active packets when a configured 1581275970Scyassociation does not exist. 1582275970ScyIt also includes 1583275970Scy.Cm pool 1584275970Scyassociations, so if you want to use servers from a 1585275970Scy.Cm pool 1586275970Scydirective and also want to use 1587275970Scy.Cm nopeer 1588275970Scyby default, you'll want a 1589275970Scy.Cm "restrict source ..." line as well that does 1590275970Scy.It not 1591275970Scyinclude the 1592275970Scy.Cm nopeer 1593275970Scydirective. 1594275970Scy.It Cm noserve 1595275970ScyDeny all packets except 1596275970Scy.Xr ntpq 1ntpqmdoc 1597275970Scyand 1598275970Scy.Xr ntpdc 1ntpdcmdoc 1599275970Scyqueries. 1600275970Scy.It Cm notrap 1601275970ScyDecline to provide mode 6 control message trap service to matching 1602275970Scyhosts. 1603275970ScyThe trap service is a subsystem of the ntpdq control message 1604275970Scyprotocol which is intended for use by remote event logging programs. 1605275970Scy.It Cm notrust 1606275970ScyDeny service unless the packet is cryptographically authenticated. 1607275970Scy.It Cm ntpport 1608275970ScyThis is actually a match algorithm modifier, rather than a 1609275970Scyrestriction flag. 1610275970ScyIts presence causes the restriction entry to be 1611275970Scymatched only if the source port in the packet is the standard NTP 1612275970ScyUDP port (123). 1613275970ScyBoth 1614275970Scy.Cm ntpport 1615275970Scyand 1616275970Scy.Cm non-ntpport 1617275970Scymay 1618275970Scybe specified. 1619275970ScyThe 1620275970Scy.Cm ntpport 1621275970Scyis considered more specific and 1622275970Scyis sorted later in the list. 1623275970Scy.It Cm version 1624275970ScyDeny packets that do not match the current NTP version. 1625275970Scy.El 1626275970Scy.Pp 1627275970ScyDefault restriction list entries with the flags ignore, interface, 1628275970Scyntpport, for each of the local host's interface addresses are 1629275970Scyinserted into the table at startup to prevent the server 1630275970Scyfrom attempting to synchronize to its own time. 1631275970ScyA default entry is also always present, though if it is 1632275970Scyotherwise unconfigured; no flags are associated 1633275970Scywith the default entry (i.e., everything besides your own 1634275970ScyNTP server is unrestricted). 1635275970Scy.El 1636275970Scy.Sh Automatic NTP Configuration Options 1637275970Scy.Ss Manycasting 1638275970ScyManycasting is a automatic discovery and configuration paradigm 1639275970Scynew to NTPv4. 1640275970ScyIt is intended as a means for a multicast client 1641275970Scyto troll the nearby network neighborhood to find cooperating 1642275970Scymanycast servers, validate them using cryptographic means 1643275970Scyand evaluate their time values with respect to other servers 1644275970Scythat might be lurking in the vicinity. 1645275970ScyThe intended result is that each manycast client mobilizes 1646275970Scyclient associations with some number of the "best" 1647275970Scyof the nearby manycast servers, yet automatically reconfigures 1648275970Scyto sustain this number of servers should one or another fail. 1649275970Scy.Pp 1650275970ScyNote that the manycasting paradigm does not coincide 1651275970Scywith the anycast paradigm described in RFC-1546, 1652275970Scywhich is designed to find a single server from a clique 1653275970Scyof servers providing the same service. 1654275970ScyThe manycast paradigm is designed to find a plurality 1655275970Scyof redundant servers satisfying defined optimality criteria. 1656275970Scy.Pp 1657275970ScyManycasting can be used with either symmetric key 1658275970Scyor public key cryptography. 1659275970ScyThe public key infrastructure (PKI) 1660275970Scyoffers the best protection against compromised keys 1661275970Scyand is generally considered stronger, at least with relatively 1662275970Scylarge key sizes. 1663275970ScyIt is implemented using the Autokey protocol and 1664275970Scythe OpenSSL cryptographic library available from 1665275970Scy.Li http://www.openssl.org/ . 1666275970ScyThe library can also be used with other NTPv4 modes 1667275970Scyas well and is highly recommended, especially for broadcast modes. 1668275970Scy.Pp 1669275970ScyA persistent manycast client association is configured 1670275970Scyusing the manycastclient command, which is similar to the 1671275970Scyserver command but with a multicast (IPv4 class 1672275970Scy.Cm D 1673275970Scyor IPv6 prefix 1674275970Scy.Cm FF ) 1675275970Scygroup address. 1676275970ScyThe IANA has designated IPv4 address 224.1.1.1 1677275970Scyand IPv6 address FF05::101 (site local) for NTP. 1678275970ScyWhen more servers are needed, it broadcasts manycast 1679275970Scyclient messages to this address at the minimum feasible rate 1680275970Scyand minimum feasible time-to-live (TTL) hops, depending 1681275970Scyon how many servers have already been found. 1682275970ScyThere can be as many manycast client associations 1683275970Scyas different group address, each one serving as a template 1684275970Scyfor a future ephemeral unicast client/server association. 1685275970Scy.Pp 1686275970ScyManycast servers configured with the 1687275970Scy.Ic manycastserver 1688275970Scycommand listen on the specified group address for manycast 1689275970Scyclient messages. 1690275970ScyNote the distinction between manycast client, 1691275970Scywhich actively broadcasts messages, and manycast server, 1692275970Scywhich passively responds to them. 1693275970ScyIf a manycast server is 1694275970Scyin scope of the current TTL and is itself synchronized 1695275970Scyto a valid source and operating at a stratum level equal 1696275970Scyto or lower than the manycast client, it replies to the 1697275970Scymanycast client message with an ordinary unicast server message. 1698275970Scy.Pp 1699275970ScyThe manycast client receiving this message mobilizes 1700275970Scyan ephemeral client/server association according to the 1701275970Scymatching manycast client template, but only if cryptographically 1702275970Scyauthenticated and the server stratum is less than or equal 1703275970Scyto the client stratum. 1704275970ScyAuthentication is explicitly required 1705275970Scyand either symmetric key or public key (Autokey) can be used. 1706275970ScyThen, the client polls the server at its unicast address 1707275970Scyin burst mode in order to reliably set the host clock 1708275970Scyand validate the source. 1709275970ScyThis normally results 1710275970Scyin a volley of eight client/server at 2-s intervals 1711275970Scyduring which both the synchronization and cryptographic 1712275970Scyprotocols run concurrently. 1713275970ScyFollowing the volley, 1714275970Scythe client runs the NTP intersection and clustering 1715275970Scyalgorithms, which act to discard all but the "best" 1716275970Scyassociations according to stratum and synchronization 1717275970Scydistance. 1718275970ScyThe surviving associations then continue 1719275970Scyin ordinary client/server mode. 1720275970Scy.Pp 1721275970ScyThe manycast client polling strategy is designed to reduce 1722275970Scyas much as possible the volume of manycast client messages 1723275970Scyand the effects of implosion due to near-simultaneous 1724275970Scyarrival of manycast server messages. 1725275970ScyThe strategy is determined by the 1726275970Scy.Ic manycastclient , 1727275970Scy.Ic tos 1728275970Scyand 1729275970Scy.Ic ttl 1730275970Scyconfiguration commands. 1731275970ScyThe manycast poll interval is 1732275970Scynormally eight times the system poll interval, 1733275970Scywhich starts out at the 1734275970Scy.Cm minpoll 1735275970Scyvalue specified in the 1736275970Scy.Ic manycastclient , 1737275970Scycommand and, under normal circumstances, increments to the 1738275970Scy.Cm maxpolll 1739275970Scyvalue specified in this command. 1740275970ScyInitially, the TTL is 1741275970Scyset at the minimum hops specified by the ttl command. 1742275970ScyAt each retransmission the TTL is increased until reaching 1743275970Scythe maximum hops specified by this command or a sufficient 1744275970Scynumber client associations have been found. 1745275970ScyFurther retransmissions use the same TTL. 1746275970Scy.Pp 1747275970ScyThe quality and reliability of the suite of associations 1748275970Scydiscovered by the manycast client is determined by the NTP 1749275970Scymitigation algorithms and the 1750275970Scy.Cm minclock 1751275970Scyand 1752275970Scy.Cm minsane 1753275970Scyvalues specified in the 1754275970Scy.Ic tos 1755275970Scyconfiguration command. 1756275970ScyAt least 1757275970Scy.Cm minsane 1758275970Scycandidate servers must be available and the mitigation 1759275970Scyalgorithms produce at least 1760275970Scy.Cm minclock 1761275970Scysurvivors in order to synchronize the clock. 1762275970ScyByzantine agreement principles require at least four 1763275970Scycandidates in order to correctly discard a single falseticker. 1764275970ScyFor legacy purposes, 1765275970Scy.Cm minsane 1766275970Scydefaults to 1 and 1767275970Scy.Cm minclock 1768275970Scydefaults to 3. 1769275970ScyFor manycast service 1770275970Scy.Cm minsane 1771275970Scyshould be explicitly set to 4, assuming at least that 1772275970Scynumber of servers are available. 1773275970Scy.Pp 1774275970ScyIf at least 1775275970Scy.Cm minclock 1776275970Scyservers are found, the manycast poll interval is immediately 1777275970Scyset to eight times 1778275970Scy.Cm maxpoll . 1779275970ScyIf less than 1780275970Scy.Cm minclock 1781275970Scyservers are found when the TTL has reached the maximum hops, 1782275970Scythe manycast poll interval is doubled. 1783275970ScyFor each transmission 1784275970Scyafter that, the poll interval is doubled again until 1785275970Scyreaching the maximum of eight times 1786275970Scy.Cm maxpoll . 1787275970ScyFurther transmissions use the same poll interval and 1788275970ScyTTL values. 1789275970ScyNote that while all this is going on, 1790275970Scyeach client/server association found is operating normally 1791275970Scyit the system poll interval. 1792275970Scy.Pp 1793275970ScyAdministratively scoped multicast boundaries are normally 1794275970Scyspecified by the network router configuration and, 1795275970Scyin the case of IPv6, the link/site scope prefix. 1796275970ScyBy default, the increment for TTL hops is 32 starting 1797275970Scyfrom 31; however, the 1798275970Scy.Ic ttl 1799275970Scyconfiguration command can be 1800275970Scyused to modify the values to match the scope rules. 1801275970Scy.Pp 1802275970ScyIt is often useful to narrow the range of acceptable 1803275970Scyservers which can be found by manycast client associations. 1804275970ScyBecause manycast servers respond only when the client 1805275970Scystratum is equal to or greater than the server stratum, 1806275970Scyprimary (stratum 1) servers fill find only primary servers 1807275970Scyin TTL range, which is probably the most common objective. 1808275970ScyHowever, unless configured otherwise, all manycast clients 1809275970Scyin TTL range will eventually find all primary servers 1810275970Scyin TTL range, which is probably not the most common 1811275970Scyobjective in large networks. 1812275970ScyThe 1813275970Scy.Ic tos 1814275970Scycommand can be used to modify this behavior. 1815275970ScyServers with stratum below 1816275970Scy.Cm floor 1817275970Scyor above 1818275970Scy.Cm ceiling 1819275970Scyspecified in the 1820275970Scy.Ic tos 1821275970Scycommand are strongly discouraged during the selection 1822275970Scyprocess; however, these servers may be temporally 1823275970Scyaccepted if the number of servers within TTL range is 1824275970Scyless than 1825275970Scy.Cm minclock . 1826275970Scy.Pp 1827275970ScyThe above actions occur for each manycast client message, 1828275970Scywhich repeats at the designated poll interval. 1829275970ScyHowever, once the ephemeral client association is mobilized, 1830275970Scysubsequent manycast server replies are discarded, 1831275970Scysince that would result in a duplicate association. 1832275970ScyIf during a poll interval the number of client associations 1833275970Scyfalls below 1834275970Scy.Cm minclock , 1835275970Scyall manycast client prototype associations are reset 1836275970Scyto the initial poll interval and TTL hops and operation 1837275970Scyresumes from the beginning. 1838275970ScyIt is important to avoid 1839275970Scyfrequent manycast client messages, since each one requires 1840275970Scyall manycast servers in TTL range to respond. 1841275970ScyThe result could well be an implosion, either minor or major, 1842275970Scydepending on the number of servers in range. 1843275970ScyThe recommended value for 1844275970Scy.Cm maxpoll 1845275970Scyis 12 (4,096 s). 1846275970Scy.Pp 1847275970ScyIt is possible and frequently useful to configure a host 1848275970Scyas both manycast client and manycast server. 1849275970ScyA number of hosts configured this way and sharing a common 1850275970Scygroup address will automatically organize themselves 1851275970Scyin an optimum configuration based on stratum and 1852275970Scysynchronization distance. 1853275970ScyFor example, consider an NTP 1854275970Scysubnet of two primary servers and a hundred or more 1855275970Scydependent clients. 1856275970ScyWith two exceptions, all servers 1857275970Scyand clients have identical configuration files including both 1858275970Scy.Ic multicastclient 1859275970Scyand 1860275970Scy.Ic multicastserver 1861275970Scycommands using, for instance, multicast group address 1862275970Scy239.1.1.1. 1863275970ScyThe only exception is that each primary server 1864275970Scyconfiguration file must include commands for the primary 1865275970Scyreference source such as a GPS receiver. 1866275970Scy.Pp 1867275970ScyThe remaining configuration files for all secondary 1868275970Scyservers and clients have the same contents, except for the 1869275970Scy.Ic tos 1870275970Scycommand, which is specific for each stratum level. 1871275970ScyFor stratum 1 and stratum 2 servers, that command is 1872275970Scynot necessary. 1873275970ScyFor stratum 3 and above servers the 1874275970Scy.Cm floor 1875275970Scyvalue is set to the intended stratum number. 1876275970ScyThus, all stratum 3 configuration files are identical, 1877275970Scyall stratum 4 files are identical and so forth. 1878275970Scy.Pp 1879275970ScyOnce operations have stabilized in this scenario, 1880275970Scythe primary servers will find the primary reference source 1881275970Scyand each other, since they both operate at the same 1882275970Scystratum (1), but not with any secondary server or client, 1883275970Scysince these operate at a higher stratum. 1884275970ScyThe secondary 1885275970Scyservers will find the servers at the same stratum level. 1886275970ScyIf one of the primary servers loses its GPS receiver, 1887275970Scyit will continue to operate as a client and other clients 1888275970Scywill time out the corresponding association and 1889275970Scyre-associate accordingly. 1890275970Scy.Pp 1891275970ScySome administrators prefer to avoid running 1892275970Scy.Xr ntpd 1ntpdmdoc 1893275970Scycontinuously and run either 1894275970Scy.Xr ntpdate 8 1895275970Scyor 1896275970Scy.Xr ntpd 1ntpdmdoc 1897275970Scy.Fl q 1898275970Scyas a cron job. 1899275970ScyIn either case the servers must be 1900275970Scyconfigured in advance and the program fails if none are 1901275970Scyavailable when the cron job runs. 1902275970ScyA really slick 1903275970Scyapplication of manycast is with 1904275970Scy.Xr ntpd 1ntpdmdoc 1905275970Scy.Fl q . 1906275970ScyThe program wakes up, scans the local landscape looking 1907275970Scyfor the usual suspects, selects the best from among 1908275970Scythe rascals, sets the clock and then departs. 1909275970ScyServers do not have to be configured in advance and 1910275970Scyall clients throughout the network can have the same 1911275970Scyconfiguration file. 1912275970Scy.Ss Manycast Interactions with Autokey 1913275970ScyEach time a manycast client sends a client mode packet 1914275970Scyto a multicast group address, all manycast servers 1915275970Scyin scope generate a reply including the host name 1916275970Scyand status word. 1917275970ScyThe manycast clients then run 1918275970Scythe Autokey protocol, which collects and verifies 1919275970Scyall certificates involved. 1920275970ScyFollowing the burst interval 1921275970Scyall but three survivors are cast off, 1922275970Scybut the certificates remain in the local cache. 1923275970ScyIt often happens that several complete signing trails 1924275970Scyfrom the client to the primary servers are collected in this way. 1925275970Scy.Pp 1926275970ScyAbout once an hour or less often if the poll interval 1927275970Scyexceeds this, the client regenerates the Autokey key list. 1928275970ScyThis is in general transparent in client/server mode. 1929275970ScyHowever, about once per day the server private value 1930275970Scyused to generate cookies is refreshed along with all 1931275970Scymanycast client associations. 1932275970ScyIn this case all 1933275970Scycryptographic values including certificates is refreshed. 1934275970ScyIf a new certificate has been generated since 1935275970Scythe last refresh epoch, it will automatically revoke 1936275970Scyall prior certificates that happen to be in the 1937275970Scycertificate cache. 1938275970ScyAt the same time, the manycast 1939275970Scyscheme starts all over from the beginning and 1940275970Scythe expanding ring shrinks to the minimum and increments 1941275970Scyfrom there while collecting all servers in scope. 1942275970Scy.Ss Manycast Options 1943275970Scy.Bl -tag -width indent 1944275970Scy.It Xo Ic tos 1945275970Scy.Oo 1946275970Scy.Cm ceiling Ar ceiling | 1947275970Scy.Cm cohort { 0 | 1 } | 1948275970Scy.Cm floor Ar floor | 1949275970Scy.Cm minclock Ar minclock | 1950275970Scy.Cm minsane Ar minsane 1951275970Scy.Oc 1952275970Scy.Xc 1953275970ScyThis command affects the clock selection and clustering 1954275970Scyalgorithms. 1955275970ScyIt can be used to select the quality and 1956275970Scyquantity of peers used to synchronize the system clock 1957275970Scyand is most useful in manycast mode. 1958275970ScyThe variables operate 1959275970Scyas follows: 1960275970Scy.Bl -tag -width indent 1961275970Scy.It Cm ceiling Ar ceiling 1962275970ScyPeers with strata above 1963275970Scy.Cm ceiling 1964275970Scywill be discarded if there are at least 1965275970Scy.Cm minclock 1966275970Scypeers remaining. 1967275970ScyThis value defaults to 15, but can be changed 1968275970Scyto any number from 1 to 15. 1969275970Scy.It Cm cohort Bro 0 | 1 Brc 1970275970ScyThis is a binary flag which enables (0) or disables (1) 1971275970Scymanycast server replies to manycast clients with the same 1972275970Scystratum level. 1973275970ScyThis is useful to reduce implosions where 1974275970Scylarge numbers of clients with the same stratum level 1975275970Scyare present. 1976275970ScyThe default is to enable these replies. 1977275970Scy.It Cm floor Ar floor 1978275970ScyPeers with strata below 1979275970Scy.Cm floor 1980275970Scywill be discarded if there are at least 1981275970Scy.Cm minclock 1982275970Scypeers remaining. 1983275970ScyThis value defaults to 1, but can be changed 1984275970Scyto any number from 1 to 15. 1985275970Scy.It Cm minclock Ar minclock 1986275970ScyThe clustering algorithm repeatedly casts out outlyer 1987275970Scyassociations until no more than 1988275970Scy.Cm minclock 1989275970Scyassociations remain. 1990275970ScyThis value defaults to 3, 1991275970Scybut can be changed to any number from 1 to the number of 1992275970Scyconfigured sources. 1993275970Scy.It Cm minsane Ar minsane 1994275970ScyThis is the minimum number of candidates available 1995275970Scyto the clock selection algorithm in order to produce 1996275970Scyone or more truechimers for the clustering algorithm. 1997275970ScyIf fewer than this number are available, the clock is 1998275970Scyundisciplined and allowed to run free. 1999275970ScyThe default is 1 2000275970Scyfor legacy purposes. 2001275970ScyHowever, according to principles of 2002275970ScyByzantine agreement, 2003275970Scy.Cm minsane 2004275970Scyshould be at least 4 in order to detect and discard 2005275970Scya single falseticker. 2006275970Scy.El 2007275970Scy.It Cm ttl Ar hop ... 2008275970ScyThis command specifies a list of TTL values in increasing 2009275970Scyorder, up to 8 values can be specified. 2010275970ScyIn manycast mode these values are used in turn 2011275970Scyin an expanding-ring search. 2012275970ScyThe default is eight 2013275970Scymultiples of 32 starting at 31. 2014275970Scy.El 2015275970Scy.Sh Reference Clock Support 2016275970ScyThe NTP Version 4 daemon supports some three dozen different radio, 2017275970Scysatellite and modem reference clocks plus a special pseudo-clock 2018275970Scyused for backup or when no other clock source is available. 2019275970ScyDetailed descriptions of individual device drivers and options can 2020275970Scybe found in the 2021275970Scy.Qq Reference Clock Drivers 2022275970Scypage 2023275970Scy(available as part of the HTML documentation 2024275970Scyprovided in 2025275970Scy.Pa /usr/share/doc/ntp ) . 2026275970ScyAdditional information can be found in the pages linked 2027275970Scythere, including the 2028275970Scy.Qq Debugging Hints for Reference Clock Drivers 2029275970Scyand 2030275970Scy.Qq How To Write a Reference Clock Driver 2031275970Scypages 2032275970Scy(available as part of the HTML documentation 2033275970Scyprovided in 2034275970Scy.Pa /usr/share/doc/ntp ) . 2035275970ScyIn addition, support for a PPS 2036275970Scysignal is available as described in the 2037275970Scy.Qq Pulse-per-second (PPS) Signal Interfacing 2038275970Scypage 2039275970Scy(available as part of the HTML documentation 2040275970Scyprovided in 2041275970Scy.Pa /usr/share/doc/ntp ) . 2042275970ScyMany 2043275970Scydrivers support special line discipline/streams modules which can 2044275970Scysignificantly improve the accuracy using the driver. 2045275970ScyThese are 2046275970Scydescribed in the 2047275970Scy.Qq Line Disciplines and Streams Drivers 2048275970Scypage 2049275970Scy(available as part of the HTML documentation 2050275970Scyprovided in 2051275970Scy.Pa /usr/share/doc/ntp ) . 2052275970Scy.Pp 2053275970ScyA reference clock will generally (though not always) be a radio 2054275970Scytimecode receiver which is synchronized to a source of standard 2055275970Scytime such as the services offered by the NRC in Canada and NIST and 2056275970ScyUSNO in the US. 2057275970ScyThe interface between the computer and the timecode 2058275970Scyreceiver is device dependent, but is usually a serial port. 2059275970ScyA 2060275970Scydevice driver specific to each reference clock must be selected and 2061275970Scycompiled in the distribution; however, most common radio, satellite 2062275970Scyand modem clocks are included by default. 2063275970ScyNote that an attempt to 2064275970Scyconfigure a reference clock when the driver has not been compiled 2065275970Scyor the hardware port has not been appropriately configured results 2066275970Scyin a scalding remark to the system log file, but is otherwise non 2067275970Scyhazardous. 2068275970Scy.Pp 2069275970ScyFor the purposes of configuration, 2070275970Scy.Xr ntpd 1ntpdmdoc 2071275970Scytreats 2072275970Scyreference clocks in a manner analogous to normal NTP peers as much 2073275970Scyas possible. 2074275970ScyReference clocks are identified by a syntactically 2075275970Scycorrect but invalid IP address, in order to distinguish them from 2076275970Scynormal NTP peers. 2077275970ScyReference clock addresses are of the form 2078275970Scy.Sm off 2079275970Scy.Li 127.127. Ar t . Ar u , 2080275970Scy.Sm on 2081275970Scywhere 2082275970Scy.Ar t 2083275970Scyis an integer 2084275970Scydenoting the clock type and 2085275970Scy.Ar u 2086275970Scyindicates the unit 2087275970Scynumber in the range 0-3. 2088275970ScyWhile it may seem overkill, it is in fact 2089275970Scysometimes useful to configure multiple reference clocks of the same 2090275970Scytype, in which case the unit numbers must be unique. 2091275970Scy.Pp 2092275970ScyThe 2093275970Scy.Ic server 2094275970Scycommand is used to configure a reference 2095275970Scyclock, where the 2096275970Scy.Ar address 2097275970Scyargument in that command 2098275970Scyis the clock address. 2099275970ScyThe 2100275970Scy.Cm key , 2101275970Scy.Cm version 2102275970Scyand 2103275970Scy.Cm ttl 2104275970Scyoptions are not used for reference clock support. 2105275970ScyThe 2106275970Scy.Cm mode 2107275970Scyoption is added for reference clock support, as 2108275970Scydescribed below. 2109275970ScyThe 2110275970Scy.Cm prefer 2111275970Scyoption can be useful to 2112275970Scypersuade the server to cherish a reference clock with somewhat more 2113275970Scyenthusiasm than other reference clocks or peers. 2114275970ScyFurther 2115275970Scyinformation on this option can be found in the 2116275970Scy.Qq Mitigation Rules and the prefer Keyword 2117275970Scy(available as part of the HTML documentation 2118275970Scyprovided in 2119275970Scy.Pa /usr/share/doc/ntp ) 2120275970Scypage. 2121275970ScyThe 2122275970Scy.Cm minpoll 2123275970Scyand 2124275970Scy.Cm maxpoll 2125275970Scyoptions have 2126275970Scymeaning only for selected clock drivers. 2127275970ScySee the individual clock 2128275970Scydriver document pages for additional information. 2129275970Scy.Pp 2130275970ScyThe 2131275970Scy.Ic fudge 2132275970Scycommand is used to provide additional 2133275970Scyinformation for individual clock drivers and normally follows 2134275970Scyimmediately after the 2135275970Scy.Ic server 2136275970Scycommand. 2137275970ScyThe 2138275970Scy.Ar address 2139275970Scyargument specifies the clock address. 2140275970ScyThe 2141275970Scy.Cm refid 2142275970Scyand 2143275970Scy.Cm stratum 2144275970Scyoptions can be used to 2145275970Scyoverride the defaults for the device. 2146275970ScyThere are two optional 2147275970Scydevice-dependent time offsets and four flags that can be included 2148275970Scyin the 2149275970Scy.Ic fudge 2150275970Scycommand as well. 2151275970Scy.Pp 2152275970ScyThe stratum number of a reference clock is by default zero. 2153275970ScySince the 2154275970Scy.Xr ntpd 1ntpdmdoc 2155275970Scydaemon adds one to the stratum of each 2156275970Scypeer, a primary server ordinarily displays an external stratum of 2157275970Scyone. 2158275970ScyIn order to provide engineered backups, it is often useful to 2159275970Scyspecify the reference clock stratum as greater than zero. 2160275970ScyThe 2161275970Scy.Cm stratum 2162275970Scyoption is used for this purpose. 2163275970ScyAlso, in cases 2164275970Scyinvolving both a reference clock and a pulse-per-second (PPS) 2165275970Scydiscipline signal, it is useful to specify the reference clock 2166275970Scyidentifier as other than the default, depending on the driver. 2167275970ScyThe 2168275970Scy.Cm refid 2169275970Scyoption is used for this purpose. 2170275970ScyExcept where noted, 2171275970Scythese options apply to all clock drivers. 2172275970Scy.Ss Reference Clock Commands 2173275970Scy.Bl -tag -width indent 2174275970Scy.It Xo Ic server 2175275970Scy.Sm off 2176275970Scy.Li 127.127. Ar t . Ar u 2177275970Scy.Sm on 2178275970Scy.Op Cm prefer 2179275970Scy.Op Cm mode Ar int 2180275970Scy.Op Cm minpoll Ar int 2181275970Scy.Op Cm maxpoll Ar int 2182275970Scy.Xc 2183275970ScyThis command can be used to configure reference clocks in 2184275970Scyspecial ways. 2185275970ScyThe options are interpreted as follows: 2186275970Scy.Bl -tag -width indent 2187275970Scy.It Cm prefer 2188275970ScyMarks the reference clock as preferred. 2189275970ScyAll other things being 2190275970Scyequal, this host will be chosen for synchronization among a set of 2191275970Scycorrectly operating hosts. 2192275970ScySee the 2193275970Scy.Qq Mitigation Rules and the prefer Keyword 2194275970Scypage 2195275970Scy(available as part of the HTML documentation 2196275970Scyprovided in 2197275970Scy.Pa /usr/share/doc/ntp ) 2198275970Scyfor further information. 2199275970Scy.It Cm mode Ar int 2200275970ScySpecifies a mode number which is interpreted in a 2201275970Scydevice-specific fashion. 2202275970ScyFor instance, it selects a dialing 2203275970Scyprotocol in the ACTS driver and a device subtype in the 2204275970Scyparse 2205275970Scydrivers. 2206275970Scy.It Cm minpoll Ar int 2207275970Scy.It Cm maxpoll Ar int 2208275970ScyThese options specify the minimum and maximum polling interval 2209275970Scyfor reference clock messages, as a power of 2 in seconds 2210275970ScyFor 2211275970Scymost directly connected reference clocks, both 2212275970Scy.Cm minpoll 2213275970Scyand 2214275970Scy.Cm maxpoll 2215275970Scydefault to 6 (64 s). 2216275970ScyFor modem reference clocks, 2217275970Scy.Cm minpoll 2218275970Scydefaults to 10 (17.1 m) and 2219275970Scy.Cm maxpoll 2220275970Scydefaults to 14 (4.5 h). 2221275970ScyThe allowable range is 4 (16 s) to 17 (36.4 h) inclusive. 2222275970Scy.El 2223275970Scy.It Xo Ic fudge 2224275970Scy.Sm off 2225275970Scy.Li 127.127. Ar t . Ar u 2226275970Scy.Sm on 2227275970Scy.Op Cm time1 Ar sec 2228275970Scy.Op Cm time2 Ar sec 2229275970Scy.Op Cm stratum Ar int 2230275970Scy.Op Cm refid Ar string 2231275970Scy.Op Cm mode Ar int 2232275970Scy.Op Cm flag1 Cm 0 \&| Cm 1 2233275970Scy.Op Cm flag2 Cm 0 \&| Cm 1 2234275970Scy.Op Cm flag3 Cm 0 \&| Cm 1 2235275970Scy.Op Cm flag4 Cm 0 \&| Cm 1 2236275970Scy.Xc 2237275970ScyThis command can be used to configure reference clocks in 2238275970Scyspecial ways. 2239275970ScyIt must immediately follow the 2240275970Scy.Ic server 2241275970Scycommand which configures the driver. 2242275970ScyNote that the same capability 2243275970Scyis possible at run time using the 2244275970Scy.Xr ntpdc 1ntpdcmdoc 2245275970Scyprogram. 2246275970ScyThe options are interpreted as 2247275970Scyfollows: 2248275970Scy.Bl -tag -width indent 2249275970Scy.It Cm time1 Ar sec 2250275970ScySpecifies a constant to be added to the time offset produced by 2251275970Scythe driver, a fixed-point decimal number in seconds. 2252275970ScyThis is used 2253275970Scyas a calibration constant to adjust the nominal time offset of a 2254275970Scyparticular clock to agree with an external standard, such as a 2255275970Scyprecision PPS signal. 2256275970ScyIt also provides a way to correct a 2257275970Scysystematic error or bias due to serial port or operating system 2258275970Scylatencies, different cable lengths or receiver internal delay. 2259275970ScyThe 2260275970Scyspecified offset is in addition to the propagation delay provided 2261275970Scyby other means, such as internal DIPswitches. 2262275970ScyWhere a calibration 2263275970Scyfor an individual system and driver is available, an approximate 2264275970Scycorrection is noted in the driver documentation pages. 2265275970ScyNote: in order to facilitate calibration when more than one 2266275970Scyradio clock or PPS signal is supported, a special calibration 2267275970Scyfeature is available. 2268275970ScyIt takes the form of an argument to the 2269275970Scy.Ic enable 2270275970Scycommand described in 2271275970Scy.Sx Miscellaneous Options 2272275970Scypage and operates as described in the 2273275970Scy.Qq Reference Clock Drivers 2274275970Scypage 2275275970Scy(available as part of the HTML documentation 2276275970Scyprovided in 2277275970Scy.Pa /usr/share/doc/ntp ) . 2278275970Scy.It Cm time2 Ar secs 2279275970ScySpecifies a fixed-point decimal number in seconds, which is 2280275970Scyinterpreted in a driver-dependent way. 2281275970ScySee the descriptions of 2282275970Scyspecific drivers in the 2283275970Scy.Qq Reference Clock Drivers 2284275970Scypage 2285275970Scy(available as part of the HTML documentation 2286275970Scyprovided in 2287275970Scy.Pa /usr/share/doc/ntp ) . 2288275970Scy.It Cm stratum Ar int 2289275970ScySpecifies the stratum number assigned to the driver, an integer 2290275970Scybetween 0 and 15. 2291275970ScyThis number overrides the default stratum number 2292275970Scyordinarily assigned by the driver itself, usually zero. 2293275970Scy.It Cm refid Ar string 2294275970ScySpecifies an ASCII string of from one to four characters which 2295275970Scydefines the reference identifier used by the driver. 2296275970ScyThis string 2297275970Scyoverrides the default identifier ordinarily assigned by the driver 2298275970Scyitself. 2299275970Scy.It Cm mode Ar int 2300275970ScySpecifies a mode number which is interpreted in a 2301275970Scydevice-specific fashion. 2302275970ScyFor instance, it selects a dialing 2303275970Scyprotocol in the ACTS driver and a device subtype in the 2304275970Scyparse 2305275970Scydrivers. 2306275970Scy.It Cm flag1 Cm 0 \&| Cm 1 2307275970Scy.It Cm flag2 Cm 0 \&| Cm 1 2308275970Scy.It Cm flag3 Cm 0 \&| Cm 1 2309275970Scy.It Cm flag4 Cm 0 \&| Cm 1 2310275970ScyThese four flags are used for customizing the clock driver. 2311275970ScyThe 2312275970Scyinterpretation of these values, and whether they are used at all, 2313275970Scyis a function of the particular clock driver. 2314275970ScyHowever, by 2315275970Scyconvention 2316275970Scy.Cm flag4 2317275970Scyis used to enable recording monitoring 2318275970Scydata to the 2319275970Scy.Cm clockstats 2320275970Scyfile configured with the 2321275970Scy.Ic filegen 2322275970Scycommand. 2323275970ScyFurther information on the 2324275970Scy.Ic filegen 2325275970Scycommand can be found in 2326275970Scy.Sx Monitoring Options . 2327275970Scy.El 2328275970Scy.El 2329275970Scy.Sh Miscellaneous Options 2330275970Scy.Bl -tag -width indent 2331275970Scy.It Ic broadcastdelay Ar seconds 2332275970ScyThe broadcast and multicast modes require a special calibration 2333275970Scyto determine the network delay between the local and remote 2334275970Scyservers. 2335275970ScyOrdinarily, this is done automatically by the initial 2336275970Scyprotocol exchanges between the client and server. 2337275970ScyIn some cases, 2338275970Scythe calibration procedure may fail due to network or server access 2339275970Scycontrols, for example. 2340275970ScyThis command specifies the default delay to 2341275970Scybe used under these circumstances. 2342275970ScyTypically (for Ethernet), a 2343275970Scynumber between 0.003 and 0.007 seconds is appropriate. 2344275970ScyThe default 2345275970Scywhen this command is not used is 0.004 seconds. 2346275970Scy.It Ic calldelay Ar delay 2347275970ScyThis option controls the delay in seconds between the first and second 2348275970Scypackets sent in burst or iburst mode to allow additional time for a modem 2349275970Scyor ISDN call to complete. 2350275970Scy.It Ic driftfile Ar driftfile 2351275970ScyThis command specifies the complete path and name of the file used to 2352275970Scyrecord the frequency of the local clock oscillator. 2353275970ScyThis is the same 2354275970Scyoperation as the 2355275970Scy.Fl f 2356275970Scycommand line option. 2357275970ScyIf the file exists, it is read at 2358275970Scystartup in order to set the initial frequency and then updated once per 2359275970Scyhour with the current frequency computed by the daemon. 2360275970ScyIf the file name is 2361275970Scyspecified, but the file itself does not exist, the starts with an initial 2362275970Scyfrequency of zero and creates the file when writing it for the first time. 2363275970ScyIf this command is not given, the daemon will always start with an initial 2364275970Scyfrequency of zero. 2365275970Scy.Pp 2366275970ScyThe file format consists of a single line containing a single 2367275970Scyfloating point number, which records the frequency offset measured 2368275970Scyin parts-per-million (PPM). 2369275970ScyThe file is updated by first writing 2370275970Scythe current drift value into a temporary file and then renaming 2371275970Scythis file to replace the old version. 2372275970ScyThis implies that 2373275970Scy.Xr ntpd 1ntpdmdoc 2374275970Scymust have write permission for the directory the 2375275970Scydrift file is located in, and that file system links, symbolic or 2376275970Scyotherwise, should be avoided. 2377275970Scy.It Xo Ic enable 2378275970Scy.Oo 2379275970Scy.Cm auth | Cm bclient | 2380275970Scy.Cm calibrate | Cm kernel | 2381275970Scy.Cm mode7 | monitor | 2382275970Scy.Cm ntp | Cm stats 2383275970Scy.Oc 2384275970Scy.Xc 2385275970Scy.It Xo Ic disable 2386275970Scy.Oo 2387275970Scy.Cm auth | Cm bclient | 2388275970Scy.Cm calibrate | Cm kernel | 2389275970Scy.Cm mode7 | monitor | 2390275970Scy.Cm ntp | Cm stats 2391275970Scy.Oc 2392275970Scy.Xc 2393275970ScyProvides a way to enable or disable various server options. 2394275970ScyFlags not mentioned are unaffected. 2395275970ScyNote that all of these flags 2396275970Scycan be controlled remotely using the 2397275970Scy.Xr ntpdc 1ntpdcmdoc 2398275970Scyutility program. 2399275970Scy.Bl -tag -width indent 2400275970Scy.It Cm auth 2401275970ScyEnables the server to synchronize with unconfigured peers only if the 2402275970Scypeer has been correctly authenticated using either public key or 2403275970Scyprivate key cryptography. 2404275970ScyThe default for this flag is 2405275970Scy.Ic enable . 2406275970Scy.It Cm bclient 2407275970ScyEnables the server to listen for a message from a broadcast or 2408275970Scymulticast server, as in the 2409275970Scy.Ic multicastclient 2410275970Scycommand with default 2411275970Scyaddress. 2412275970ScyThe default for this flag is 2413275970Scy.Ic disable . 2414275970Scy.It Cm calibrate 2415275970ScyEnables the calibrate feature for reference clocks. 2416275970ScyThe default for 2417275970Scythis flag is 2418275970Scy.Ic disable . 2419275970Scy.It Cm kernel 2420275970ScyEnables the kernel time discipline, if available. 2421275970ScyThe default for this 2422275970Scyflag is 2423275970Scy.Ic enable 2424275970Scyif support is available, otherwise 2425275970Scy.Ic disable . 2426275970Scy.It Cm mode7 2427275970ScyEnables processing of NTP mode 7 implementation-specific requests 2428275970Scywhich are used by the deprecated 2429275970Scy.Xr ntpdc 1ntpdcmdoc 2430275970Scyprogram. 2431275970ScyThe default for this flag is disable. 2432275970ScyThis flag is excluded from runtime configuration using 2433275970Scy.Xr ntpq 1ntpqmdoc . 2434275970ScyThe 2435275970Scy.Xr ntpq 1ntpqmdoc 2436275970Scyprogram provides the same capabilities as 2437275970Scy.Xr ntpdc 1ntpdcmdoc 2438275970Scyusing standard mode 6 requests. 2439275970Scy.It Cm monitor 2440275970ScyEnables the monitoring facility. 2441275970ScySee the 2442275970Scy.Xr ntpdc 1ntpdcmdoc 2443275970Scyprogram 2444275970Scyand the 2445275970Scy.Ic monlist 2446275970Scycommand or further information. 2447275970ScyThe 2448275970Scydefault for this flag is 2449275970Scy.Ic enable . 2450275970Scy.It Cm ntp 2451275970ScyEnables time and frequency discipline. 2452275970ScyIn effect, this switch opens and 2453275970Scycloses the feedback loop, which is useful for testing. 2454275970ScyThe default for 2455275970Scythis flag is 2456275970Scy.Ic enable . 2457275970Scy.It Cm stats 2458275970ScyEnables the statistics facility. 2459275970ScySee the 2460275970Scy.Sx Monitoring Options 2461275970Scysection for further information. 2462275970ScyThe default for this flag is 2463275970Scy.Ic disable . 2464275970Scy.El 2465275970Scy.It Ic includefile Ar includefile 2466275970ScyThis command allows additional configuration commands 2467275970Scyto be included from a separate file. 2468275970ScyInclude files may 2469275970Scybe nested to a depth of five; upon reaching the end of any 2470275970Scyinclude file, command processing resumes in the previous 2471275970Scyconfiguration file. 2472275970ScyThis option is useful for sites that run 2473275970Scy.Xr ntpd 1ntpdmdoc 2474275970Scyon multiple hosts, with (mostly) common options (e.g., a 2475275970Scyrestriction list). 2476275970Scy.It Ic logconfig Ar configkeyword 2477275970ScyThis command controls the amount and type of output written to 2478275970Scythe system 2479275970Scy.Xr syslog 3 2480275970Scyfacility or the alternate 2481275970Scy.Ic logfile 2482275970Scylog file. 2483275970ScyBy default, all output is turned on. 2484275970ScyAll 2485275970Scy.Ar configkeyword 2486275970Scykeywords can be prefixed with 2487275970Scy.Ql = , 2488275970Scy.Ql + 2489275970Scyand 2490275970Scy.Ql - , 2491275970Scywhere 2492275970Scy.Ql = 2493275970Scysets the 2494275970Scy.Xr syslog 3 2495275970Scypriority mask, 2496275970Scy.Ql + 2497275970Scyadds and 2498275970Scy.Ql - 2499275970Scyremoves 2500275970Scymessages. 2501275970Scy.Xr syslog 3 2502275970Scymessages can be controlled in four 2503275970Scyclasses 2504275970Scy.Po 2505275970Scy.Cm clock , 2506275970Scy.Cm peer , 2507275970Scy.Cm sys 2508275970Scyand 2509275970Scy.Cm sync 2510275970Scy.Pc . 2511275970ScyWithin these classes four types of messages can be 2512275970Scycontrolled: informational messages 2513275970Scy.Po 2514275970Scy.Cm info 2515275970Scy.Pc , 2516275970Scyevent messages 2517275970Scy.Po 2518275970Scy.Cm events 2519275970Scy.Pc , 2520275970Scystatistics messages 2521275970Scy.Po 2522275970Scy.Cm statistics 2523275970Scy.Pc 2524275970Scyand 2525275970Scystatus messages 2526275970Scy.Po 2527275970Scy.Cm status 2528275970Scy.Pc . 2529275970Scy.Pp 2530275970ScyConfiguration keywords are formed by concatenating the message class with 2531275970Scythe event class. 2532275970ScyThe 2533275970Scy.Cm all 2534275970Scyprefix can be used instead of a message class. 2535275970ScyA 2536275970Scymessage class may also be followed by the 2537275970Scy.Cm all 2538275970Scykeyword to enable/disable all 2539275970Scymessages of the respective message class.Thus, a minimal log configuration 2540275970Scycould look like this: 2541275970Scy.Bd -literal 2542275970Scylogconfig =syncstatus +sysevents 2543275970Scy.Ed 2544275970Scy.Pp 2545275970ScyThis would just list the synchronizations state of 2546275970Scy.Xr ntpd 1ntpdmdoc 2547275970Scyand the major system events. 2548275970ScyFor a simple reference server, the 2549275970Scyfollowing minimum message configuration could be useful: 2550275970Scy.Bd -literal 2551275970Scylogconfig =syncall +clockall 2552275970Scy.Ed 2553275970Scy.Pp 2554275970ScyThis configuration will list all clock information and 2555275970Scysynchronization information. 2556275970ScyAll other events and messages about 2557275970Scypeers, system events and so on is suppressed. 2558275970Scy.It Ic logfile Ar logfile 2559275970ScyThis command specifies the location of an alternate log file to 2560275970Scybe used instead of the default system 2561275970Scy.Xr syslog 3 2562275970Scyfacility. 2563275970ScyThis is the same operation as the -l command line option. 2564275970Scy.It Ic setvar Ar variable Op Cm default 2565275970ScyThis command adds an additional system variable. 2566275970ScyThese 2567275970Scyvariables can be used to distribute additional information such as 2568275970Scythe access policy. 2569275970ScyIf the variable of the form 2570275970Scy.Sm off 2571275970Scy.Va name = Ar value 2572275970Scy.Sm on 2573275970Scyis followed by the 2574275970Scy.Cm default 2575275970Scykeyword, the 2576275970Scyvariable will be listed as part of the default system variables 2577275970Scy.Po 2578275970Scy.Xr ntpq 1ntpqmdoc 2579275970Scy.Ic rv 2580275970Scycommand 2581275970Scy.Pc ) . 2582275970ScyThese additional variables serve 2583275970Scyinformational purposes only. 2584275970ScyThey are not related to the protocol 2585275970Scyother that they can be listed. 2586275970ScyThe known protocol variables will 2587275970Scyalways override any variables defined via the 2588275970Scy.Ic setvar 2589275970Scymechanism. 2590275970ScyThere are three special variables that contain the names 2591275970Scyof all variable of the same group. 2592275970ScyThe 2593275970Scy.Va sys_var_list 2594275970Scyholds 2595275970Scythe names of all system variables. 2596275970ScyThe 2597275970Scy.Va peer_var_list 2598275970Scyholds 2599275970Scythe names of all peer variables and the 2600275970Scy.Va clock_var_list 2601275970Scyholds the names of the reference clock variables. 2602275970Scy.It Xo Ic tinker 2603275970Scy.Oo 2604275970Scy.Cm allan Ar allan | 2605275970Scy.Cm dispersion Ar dispersion | 2606275970Scy.Cm freq Ar freq | 2607275970Scy.Cm huffpuff Ar huffpuff | 2608275970Scy.Cm panic Ar panic | 2609275970Scy.Cm step Ar srep | 2610275970Scy.Cm stepout Ar stepout 2611275970Scy.Oc 2612275970Scy.Xc 2613275970ScyThis command can be used to alter several system variables in 2614275970Scyvery exceptional circumstances. 2615275970ScyIt should occur in the 2616275970Scyconfiguration file before any other configuration options. 2617275970ScyThe 2618275970Scydefault values of these variables have been carefully optimized for 2619275970Scya wide range of network speeds and reliability expectations. 2620275970ScyIn 2621275970Scygeneral, they interact in intricate ways that are hard to predict 2622275970Scyand some combinations can result in some very nasty behavior. 2623275970ScyVery 2624275970Scyrarely is it necessary to change the default values; but, some 2625275970Scyfolks cannot resist twisting the knobs anyway and this command is 2626275970Scyfor them. 2627275970ScyEmphasis added: twisters are on their own and can expect 2628275970Scyno help from the support group. 2629275970Scy.Pp 2630275970ScyThe variables operate as follows: 2631275970Scy.Bl -tag -width indent 2632275970Scy.It Cm allan Ar allan 2633275970ScyThe argument becomes the new value for the minimum Allan 2634275970Scyintercept, which is a parameter of the PLL/FLL clock discipline 2635275970Scyalgorithm. 2636275970ScyThe value in log2 seconds defaults to 7 (1024 s), which is also the lower 2637275970Scylimit. 2638275970Scy.It Cm dispersion Ar dispersion 2639275970ScyThe argument becomes the new value for the dispersion increase rate, 2640275970Scynormally .000015 s/s. 2641275970Scy.It Cm freq Ar freq 2642275970ScyThe argument becomes the initial value of the frequency offset in 2643275970Scyparts-per-million. 2644275970ScyThis overrides the value in the frequency file, if 2645275970Scypresent, and avoids the initial training state if it is not. 2646275970Scy.It Cm huffpuff Ar huffpuff 2647275970ScyThe argument becomes the new value for the experimental 2648275970Scyhuff-n'-puff filter span, which determines the most recent interval 2649275970Scythe algorithm will search for a minimum delay. 2650275970ScyThe lower limit is 2651275970Scy900 s (15 m), but a more reasonable value is 7200 (2 hours). 2652275970ScyThere 2653275970Scyis no default, since the filter is not enabled unless this command 2654275970Scyis given. 2655275970Scy.It Cm panic Ar panic 2656275970ScyThe argument is the panic threshold, normally 1000 s. 2657275970ScyIf set to zero, 2658275970Scythe panic sanity check is disabled and a clock offset of any value will 2659275970Scybe accepted. 2660275970Scy.It Cm step Ar step 2661275970ScyThe argument is the step threshold, which by default is 0.128 s. 2662275970ScyIt can 2663275970Scybe set to any positive number in seconds. 2664275970ScyIf set to zero, step 2665275970Scyadjustments will never occur. 2666275970ScyNote: The kernel time discipline is 2667275970Scydisabled if the step threshold is set to zero or greater than the 2668275970Scydefault. 2669275970Scy.It Cm stepout Ar stepout 2670275970ScyThe argument is the stepout timeout, which by default is 900 s. 2671275970ScyIt can 2672275970Scybe set to any positive number in seconds. 2673275970ScyIf set to zero, the stepout 2674275970Scypulses will not be suppressed. 2675275970Scy.El 2676275970Scy.It Xo Ic rlimit 2677275970Scy.Oo 2678275970Scy.Cm memlock Ar Nmegabytes | 2679275970Scy.Cm stacksize Ar N4kPages 2680275970Scy.Cm filenum Ar Nfiledescriptors 2681275970Scy.Oc 2682275970Scy.Xc 2683275970Scy.Bl -tag -width indent 2684275970Scy.It Cm memlock Ar Nmegabytes 2685275970ScySpecify the number of megabytes of memory that can be allocated. 2686275970ScyProbably only available under Linux, this option is useful 2687275970Scywhen dropping root (the 2688275970Scy.Fl i 2689275970Scyoption). 2690275970ScyThe default is 32 megabytes. Setting this to zero will prevent any attemp to lock memory. 2691275970Scy.It Cm stacksize Ar N4kPages 2692275970ScySpecifies the maximum size of the process stack on systems with the 2693275970Scy.It Cm filenum Ar Nfiledescriptors 2694275970ScySpecifies the maximum number of file descriptors ntpd may have open at once. Defaults to the system default. 2695275970Scy.Fn mlockall 2696275970Scyfunction. 2697275970ScyDefaults to 50 4k pages (200 4k pages in OpenBSD). 2698275970Scy.El 2699275970Scy.It Xo Ic trap Ar host_address 2700275970Scy.Op Cm port Ar port_number 2701275970Scy.Op Cm interface Ar interface_address 2702275970Scy.Xc 2703275970ScyThis command configures a trap receiver at the given host 2704275970Scyaddress and port number for sending messages with the specified 2705275970Scylocal interface address. 2706275970ScyIf the port number is unspecified, a value 2707275970Scyof 18447 is used. 2708275970ScyIf the interface address is not specified, the 2709275970Scymessage is sent with a source address of the local interface the 2710275970Scymessage is sent through. 2711275970ScyNote that on a multihomed host the 2712275970Scyinterface used may vary from time to time with routing changes. 2713275970Scy.Pp 2714275970ScyThe trap receiver will generally log event messages and other 2715275970Scyinformation from the server in a log file. 2716275970ScyWhile such monitor 2717275970Scyprograms may also request their own trap dynamically, configuring a 2718275970Scytrap receiver will ensure that no messages are lost when the server 2719275970Scyis started. 2720275970Scy.It Cm hop Ar ... 2721275970ScyThis command specifies a list of TTL values in increasing order, up to 8 2722275970Scyvalues can be specified. 2723275970ScyIn manycast mode these values are used in turn in 2724275970Scyan expanding-ring search. 2725275970ScyThe default is eight multiples of 32 starting at 2726275970Scy31. 2727275970Scy.El 2728275970Scy _END_PROG_MDOC_DESCRIP; 2729275970Scy}; 2730275970Scy 2731275970Scydoc-section = { 2732275970Scy ds-type = 'FILES'; 2733275970Scy ds-format = 'mdoc'; 2734275970Scy ds-text = <<- _END_MDOC_FILES 2735275970Scy.Bl -tag -width /etc/ntp.drift -compact 2736275970Scy.It Pa /etc/ntp.conf 2737275970Scythe default name of the configuration file 2738275970Scy.It Pa ntp.keys 2739275970Scyprivate MD5 keys 2740275970Scy.It Pa ntpkey 2741275970ScyRSA private key 2742275970Scy.It Pa ntpkey_ Ns Ar host 2743275970ScyRSA public key 2744275970Scy.It Pa ntp_dh 2745275970ScyDiffie-Hellman agreement parameters 2746275970Scy.El 2747275970Scy _END_MDOC_FILES; 2748275970Scy}; 2749275970Scy 2750275970Scydoc-section = { 2751275970Scy ds-type = 'SEE ALSO'; 2752275970Scy ds-format = 'mdoc'; 2753275970Scy ds-text = <<- _END_MDOC_SEE_ALSO 2754275970Scy.Xr ntpd 1ntpdmdoc , 2755275970Scy.Xr ntpdc 1ntpdcmdoc , 2756275970Scy.Xr ntpq 1ntpqmdoc 2757275970Scy.Pp 2758275970ScyIn addition to the manual pages provided, 2759275970Scycomprehensive documentation is available on the world wide web 2760275970Scyat 2761275970Scy.Li http://www.ntp.org/ . 2762275970ScyA snapshot of this documentation is available in HTML format in 2763275970Scy.Pa /usr/share/doc/ntp . 2764275970Scy.Rs 2765275970Scy.%A David L. Mills 2766275970Scy.%T Network Time Protocol (Version 4) 2767275970Scy.%O RFC5905 2768275970Scy.Re 2769275970Scy _END_MDOC_SEE_ALSO; 2770275970Scy}; 2771275970Scy 2772275970Scydoc-section = { 2773275970Scy ds-type = 'BUGS'; 2774275970Scy ds-format = 'mdoc'; 2775275970Scy ds-text = <<- _END_MDOC_BUGS 2776275970ScyThe syntax checking is not picky; some combinations of 2777275970Scyridiculous and even hilarious options and modes may not be 2778275970Scydetected. 2779275970Scy.Pp 2780275970ScyThe 2781275970Scy.Pa ntpkey_ Ns Ar host 2782275970Scyfiles are really digital 2783275970Scycertificates. 2784275970ScyThese should be obtained via secure directory 2785275970Scyservices when they become universally available. 2786275970Scy _END_MDOC_BUGS; 2787275970Scy}; 2788275970Scy 2789275970Scydoc-section = { 2790275970Scy ds-type = 'NOTES'; 2791275970Scy ds-format = 'mdoc'; 2792275970Scy ds-text = <<- _END_MDOC_NOTES 2793275970ScyThis document was derived from FreeBSD. 2794275970Scy _END_MDOC_NOTES; 2795275970Scy}; 2796