ntp.conf.5mdoc revision 298770
1298770Sdelphij.Dd April 26 2016 2275970Scy.Dt NTP_CONF 5mdoc File Formats 3275970Scy.Os 4275970Scy.\" EDIT THIS FILE WITH CAUTION (ntp.mdoc) 5275970Scy.\" 6298770Sdelphij.\" It has been AutoGen-ed April 26, 2016 at 08:28:36 PM by AutoGen 5.18.5 7275970Scy.\" From the definitions ntp.conf.def 8275970Scy.\" and the template file agmdoc-cmd.tpl 9275970Scy.Sh NAME 10275970Scy.Nm ntp.conf 11275970Scy.Nd Network Time Protocol (NTP) daemon configuration file format 12275970Scy.Sh SYNOPSIS 13275970Scy.Nm 14275970Scy.Op Fl \-option\-name 15275970Scy.Op Fl \-option\-name Ar value 16275970Scy.Pp 17275970ScyAll arguments must be options. 18275970Scy.Pp 19275970Scy.Sh DESCRIPTION 20275970ScyThe 21275970Scy.Nm 22275970Scyconfiguration file is read at initial startup by the 23275970Scy.Xr ntpd 1ntpdmdoc 24275970Scydaemon in order to specify the synchronization sources, 25275970Scymodes and other related information. 26275970ScyUsually, it is installed in the 27275970Scy.Pa /etc 28275970Scydirectory, 29275970Scybut could be installed elsewhere 30275970Scy(see the daemon's 31275970Scy.Fl c 32275970Scycommand line option). 33275970Scy.Pp 34275970ScyThe file format is similar to other 35275970Scy.Ux 36275970Scyconfiguration files. 37275970ScyComments begin with a 38275970Scy.Ql # 39275970Scycharacter and extend to the end of the line; 40275970Scyblank lines are ignored. 41275970ScyConfiguration commands consist of an initial keyword 42275970Scyfollowed by a list of arguments, 43275970Scysome of which may be optional, separated by whitespace. 44275970ScyCommands may not be continued over multiple lines. 45275970ScyArguments may be host names, 46275970Scyhost addresses written in numeric, dotted\-quad form, 47275970Scyintegers, floating point numbers (when specifying times in seconds) 48275970Scyand text strings. 49275970Scy.Pp 50275970ScyThe rest of this page describes the configuration and control options. 51275970ScyThe 52275970Scy.Qq Notes on Configuring NTP and Setting up an NTP Subnet 53275970Scypage 54275970Scy(available as part of the HTML documentation 55275970Scyprovided in 56275970Scy.Pa /usr/share/doc/ntp ) 57275970Scycontains an extended discussion of these options. 58275970ScyIn addition to the discussion of general 59275970Scy.Sx Configuration Options , 60275970Scythere are sections describing the following supported functionality 61275970Scyand the options used to control it: 62275970Scy.Bl -bullet -offset indent 63275970Scy.It 64275970Scy.Sx Authentication Support 65275970Scy.It 66275970Scy.Sx Monitoring Support 67275970Scy.It 68275970Scy.Sx Access Control Support 69275970Scy.It 70275970Scy.Sx Automatic NTP Configuration Options 71275970Scy.It 72275970Scy.Sx Reference Clock Support 73275970Scy.It 74275970Scy.Sx Miscellaneous Options 75275970Scy.El 76275970Scy.Pp 77275970ScyFollowing these is a section describing 78275970Scy.Sx Miscellaneous Options . 79275970ScyWhile there is a rich set of options available, 80275970Scythe only required option is one or more 81275970Scy.Ic pool , 82275970Scy.Ic server , 83275970Scy.Ic peer , 84275970Scy.Ic broadcast 85275970Scyor 86275970Scy.Ic manycastclient 87275970Scycommands. 88275970Scy.Sh Configuration Support 89275970ScyFollowing is a description of the configuration commands in 90275970ScyNTPv4. 91275970ScyThese commands have the same basic functions as in NTPv3 and 92275970Scyin some cases new functions and new arguments. 93275970ScyThere are two 94275970Scyclasses of commands, configuration commands that configure a 95275970Scypersistent association with a remote server or peer or reference 96275970Scyclock, and auxiliary commands that specify environmental variables 97275970Scythat control various related operations. 98275970Scy.Ss Configuration Commands 99275970ScyThe various modes are determined by the command keyword and the 100275970Scytype of the required IP address. 101275970ScyAddresses are classed by type as 102275970Scy(s) a remote server or peer (IPv4 class A, B and C), (b) the 103275970Scybroadcast address of a local interface, (m) a multicast address (IPv4 104275970Scyclass D), or (r) a reference clock address (127.127.x.x). 105275970ScyNote that 106275970Scyonly those options applicable to each command are listed below. 107275970ScyUse 108275970Scyof options not listed may not be caught as an error, but may result 109275970Scyin some weird and even destructive behavior. 110275970Scy.Pp 111275970ScyIf the Basic Socket Interface Extensions for IPv6 (RFC\-2553) 112275970Scyis detected, support for the IPv6 address family is generated 113275970Scyin addition to the default support of the IPv4 address family. 114298770SdelphijIn a few cases, including the 115298770Sdelphij.Cm reslist 116298770Sdelphijbillboard generated 117298770Sdelphijby 118298770Sdelphij.Xr ntpq 1ntpqmdoc 119298770Sdelphijor 120298770Sdelphij.Xr ntpdc 1ntpdcmdoc , 121298770SdelphijIPv6 addresses are automatically generated. 122275970ScyIPv6 addresses can be identified by the presence of colons 123275970Scy.Dq \&: 124275970Scyin the address field. 125275970ScyIPv6 addresses can be used almost everywhere where 126275970ScyIPv4 addresses can be used, 127275970Scywith the exception of reference clock addresses, 128275970Scywhich are always IPv4. 129275970Scy.Pp 130275970ScyNote that in contexts where a host name is expected, a 131275970Scy.Fl 4 132275970Scyqualifier preceding 133275970Scythe host name forces DNS resolution to the IPv4 namespace, 134275970Scywhile a 135275970Scy.Fl 6 136275970Scyqualifier forces DNS resolution to the IPv6 namespace. 137275970ScySee IPv6 references for the 138275970Scyequivalent classes for that address family. 139275970Scy.Bl -tag -width indent 140275970Scy.It Xo Ic pool Ar address 141275970Scy.Op Cm burst 142275970Scy.Op Cm iburst 143275970Scy.Op Cm version Ar version 144275970Scy.Op Cm prefer 145275970Scy.Op Cm minpoll Ar minpoll 146275970Scy.Op Cm maxpoll Ar maxpoll 147275970Scy.Xc 148275970Scy.It Xo Ic server Ar address 149275970Scy.Op Cm key Ar key \&| Cm autokey 150275970Scy.Op Cm burst 151275970Scy.Op Cm iburst 152275970Scy.Op Cm version Ar version 153275970Scy.Op Cm prefer 154275970Scy.Op Cm minpoll Ar minpoll 155275970Scy.Op Cm maxpoll Ar maxpoll 156298770Sdelphij.Op Cm true 157275970Scy.Xc 158275970Scy.It Xo Ic peer Ar address 159275970Scy.Op Cm key Ar key \&| Cm autokey 160275970Scy.Op Cm version Ar version 161275970Scy.Op Cm prefer 162275970Scy.Op Cm minpoll Ar minpoll 163275970Scy.Op Cm maxpoll Ar maxpoll 164298770Sdelphij.Op Cm true 165298770Sdelphij.Op Cm xleave 166275970Scy.Xc 167275970Scy.It Xo Ic broadcast 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 ttl Ar ttl 173298770Sdelphij.Op Cm xleave 174275970Scy.Xc 175275970Scy.It Xo Ic manycastclient Ar address 176275970Scy.Op Cm key Ar key \&| Cm autokey 177275970Scy.Op Cm version Ar version 178275970Scy.Op Cm prefer 179275970Scy.Op Cm minpoll Ar minpoll 180275970Scy.Op Cm maxpoll Ar maxpoll 181275970Scy.Op Cm ttl Ar ttl 182275970Scy.Xc 183275970Scy.El 184275970Scy.Pp 185275970ScyThese five commands specify the time server name or address to 186275970Scybe used and the mode in which to operate. 187275970ScyThe 188275970Scy.Ar address 189275970Scycan be 190275970Scyeither a DNS name or an IP address in dotted\-quad notation. 191275970ScyAdditional information on association behavior can be found in the 192275970Scy.Qq Association Management 193275970Scypage 194275970Scy(available as part of the HTML documentation 195275970Scyprovided in 196275970Scy.Pa /usr/share/doc/ntp ) . 197275970Scy.Bl -tag -width indent 198275970Scy.It Ic pool 199275970ScyFor type s addresses, this command mobilizes a persistent 200275970Scyclient mode association with a number of remote servers. 201275970ScyIn this mode the local clock can synchronized to the 202275970Scyremote server, but the remote server can never be synchronized to 203275970Scythe local clock. 204275970Scy.It Ic server 205275970ScyFor type s and r addresses, this command mobilizes a persistent 206275970Scyclient mode association with the specified remote server or local 207275970Scyradio clock. 208275970ScyIn this mode the local clock can synchronized to the 209275970Scyremote server, but the remote server can never be synchronized to 210275970Scythe local clock. 211275970ScyThis command should 212275970Scy.Em not 213275970Scybe used for type 214275970Scyb or m addresses. 215275970Scy.It Ic peer 216275970ScyFor type s addresses (only), this command mobilizes a 217275970Scypersistent symmetric\-active mode association with the specified 218275970Scyremote peer. 219275970ScyIn this mode the local clock can be synchronized to 220275970Scythe remote peer or the remote peer can be synchronized to the local 221275970Scyclock. 222275970ScyThis is useful in a network of servers where, depending on 223275970Scyvarious failure scenarios, either the local or remote peer may be 224275970Scythe better source of time. 225275970ScyThis command should NOT be used for type 226275970Scyb, m or r addresses. 227275970Scy.It Ic broadcast 228275970ScyFor type b and m addresses (only), this 229275970Scycommand mobilizes a persistent broadcast mode association. 230275970ScyMultiple 231275970Scycommands can be used to specify multiple local broadcast interfaces 232275970Scy(subnets) and/or multiple multicast groups. 233275970ScyNote that local 234275970Scybroadcast messages go only to the interface associated with the 235275970Scysubnet specified, but multicast messages go to all interfaces. 236275970ScyIn broadcast mode the local server sends periodic broadcast 237275970Scymessages to a client population at the 238275970Scy.Ar address 239275970Scyspecified, which is usually the broadcast address on (one of) the 240275970Scylocal network(s) or a multicast address assigned to NTP. 241275970ScyThe IANA 242275970Scyhas assigned the multicast group address IPv4 224.0.1.1 and 243275970ScyIPv6 ff05::101 (site local) exclusively to 244275970ScyNTP, but other nonconflicting addresses can be used to contain the 245275970Scymessages within administrative boundaries. 246275970ScyOrdinarily, this 247275970Scyspecification applies only to the local server operating as a 248275970Scysender; for operation as a broadcast client, see the 249275970Scy.Ic broadcastclient 250275970Scyor 251275970Scy.Ic multicastclient 252275970Scycommands 253275970Scybelow. 254275970Scy.It Ic manycastclient 255275970ScyFor type m addresses (only), this command mobilizes a 256275970Scymanycast client mode association for the multicast address 257275970Scyspecified. 258275970ScyIn this case a specific address must be supplied which 259275970Scymatches the address used on the 260275970Scy.Ic manycastserver 261275970Scycommand for 262275970Scythe designated manycast servers. 263275970ScyThe NTP multicast address 264275970Scy224.0.1.1 assigned by the IANA should NOT be used, unless specific 265275970Scymeans are taken to avoid spraying large areas of the Internet with 266275970Scythese messages and causing a possibly massive implosion of replies 267275970Scyat the sender. 268275970ScyThe 269275970Scy.Ic manycastserver 270275970Scycommand specifies that the local server 271275970Scyis to operate in client mode with the remote servers that are 272275970Scydiscovered as the result of broadcast/multicast messages. 273275970ScyThe 274275970Scyclient broadcasts a request message to the group address associated 275275970Scywith the specified 276275970Scy.Ar address 277275970Scyand specifically enabled 278275970Scyservers respond to these messages. 279275970ScyThe client selects the servers 280275970Scyproviding the best time and continues as with the 281275970Scy.Ic server 282275970Scycommand. 283275970ScyThe remaining servers are discarded as if never 284275970Scyheard. 285275970Scy.El 286275970Scy.Pp 287275970ScyOptions: 288275970Scy.Bl -tag -width indent 289275970Scy.It Cm autokey 290275970ScyAll packets sent to and received from the server or peer are to 291275970Scyinclude authentication fields encrypted using the autokey scheme 292275970Scydescribed in 293275970Scy.Sx Authentication Options . 294275970Scy.It Cm burst 295275970Scywhen the server is reachable, send a burst of eight packets 296275970Scyinstead of the usual one. 297275970ScyThe packet spacing is normally 2 s; 298275970Scyhowever, the spacing between the first and second packets 299298770Sdelphijcan be changed with the 300298770Sdelphij.Ic calldelay 301298770Sdelphijcommand to allow 302275970Scyadditional time for a modem or ISDN call to complete. 303275970ScyThis is designed to improve timekeeping quality 304275970Scywith the 305275970Scy.Ic server 306275970Scycommand and s addresses. 307275970Scy.It Cm iburst 308275970ScyWhen the server is unreachable, send a burst of eight packets 309275970Scyinstead of the usual one. 310275970ScyThe packet spacing is normally 2 s; 311275970Scyhowever, the spacing between the first two packets can be 312298770Sdelphijchanged with the 313298770Sdelphij.Ic calldelay 314298770Sdelphijcommand to allow 315275970Scyadditional time for a modem or ISDN call to complete. 316275970ScyThis is designed to speed the initial synchronization 317275970Scyacquisition with the 318275970Scy.Ic server 319275970Scycommand and s addresses and when 320275970Scy.Xr ntpd 1ntpdmdoc 321275970Scyis started with the 322275970Scy.Fl q 323275970Scyoption. 324275970Scy.It Cm key Ar key 325275970ScyAll packets sent to and received from the server or peer are to 326275970Scyinclude authentication fields encrypted using the specified 327275970Scy.Ar key 328275970Scyidentifier with values from 1 to 65534, inclusive. 329275970ScyThe 330275970Scydefault is to include no encryption field. 331275970Scy.It Cm minpoll Ar minpoll 332275970Scy.It Cm maxpoll Ar maxpoll 333275970ScyThese options specify the minimum and maximum poll intervals 334275970Scyfor NTP messages, as a power of 2 in seconds 335275970ScyThe maximum poll 336275970Scyinterval defaults to 10 (1,024 s), but can be increased by the 337275970Scy.Cm maxpoll 338275970Scyoption to an upper limit of 17 (36.4 h). 339275970ScyThe 340275970Scyminimum poll interval defaults to 6 (64 s), but can be decreased by 341275970Scythe 342275970Scy.Cm minpoll 343275970Scyoption to a lower limit of 4 (16 s). 344275970Scy.It Cm noselect 345275970ScyMarks the server as unused, except for display purposes. 346275970ScyThe server is discarded by the selection algroithm. 347298770Sdelphij.It Cm preempt 348298770SdelphijSays the association can be preempted. 349298770Sdelphij.It Cm true 350298770SdelphijMarks the server as a truechimer. 351298770SdelphijUse this option only for testing. 352275970Scy.It Cm prefer 353275970ScyMarks the server as preferred. 354275970ScyAll other things being equal, 355275970Scythis host will be chosen for synchronization among a set of 356275970Scycorrectly operating hosts. 357275970ScySee the 358275970Scy.Qq Mitigation Rules and the prefer Keyword 359275970Scypage 360275970Scy(available as part of the HTML documentation 361275970Scyprovided in 362275970Scy.Pa /usr/share/doc/ntp ) 363275970Scyfor further information. 364298770Sdelphij.It Cm true 365298770SdelphijForces the association to always survive the selection and clustering algorithms. 366298770SdelphijThis option should almost certainly 367298770Sdelphij.Em only 368298770Sdelphijbe used while testing an association. 369275970Scy.It Cm ttl Ar ttl 370275970ScyThis option is used only with broadcast server and manycast 371275970Scyclient modes. 372275970ScyIt specifies the time\-to\-live 373275970Scy.Ar ttl 374275970Scyto 375275970Scyuse on broadcast server and multicast server and the maximum 376275970Scy.Ar ttl 377275970Scyfor the expanding ring search with manycast 378275970Scyclient packets. 379275970ScySelection of the proper value, which defaults to 380275970Scy127, is something of a black art and should be coordinated with the 381275970Scynetwork administrator. 382275970Scy.It Cm version Ar version 383275970ScySpecifies the version number to be used for outgoing NTP 384275970Scypackets. 385275970ScyVersions 1\-4 are the choices, with version 4 the 386275970Scydefault. 387298770Sdelphij.It Cm xleave 388298770SdelphijValid in 389298770Sdelphij.Cm peer 390298770Sdelphijand 391298770Sdelphij.Cm broadcast 392298770Sdelphijmodes only, this flag enables interleave mode. 393275970Scy.El 394275970Scy.Ss Auxiliary Commands 395275970Scy.Bl -tag -width indent 396275970Scy.It Ic broadcastclient 397275970ScyThis command enables reception of broadcast server messages to 398275970Scyany local interface (type b) address. 399275970ScyUpon receiving a message for 400275970Scythe first time, the broadcast client measures the nominal server 401275970Scypropagation delay using a brief client/server exchange with the 402275970Scyserver, then enters the broadcast client mode, in which it 403275970Scysynchronizes to succeeding broadcast messages. 404275970ScyNote that, in order 405275970Scyto avoid accidental or malicious disruption in this mode, both the 406275970Scyserver and client should operate using symmetric\-key or public\-key 407275970Scyauthentication as described in 408275970Scy.Sx Authentication Options . 409275970Scy.It Ic manycastserver Ar address ... 410275970ScyThis command enables reception of manycast client messages to 411275970Scythe multicast group address(es) (type m) specified. 412275970ScyAt least one 413275970Scyaddress is required, but the NTP multicast address 224.0.1.1 414275970Scyassigned by the IANA should NOT be used, unless specific means are 415275970Scytaken to limit the span of the reply and avoid a possibly massive 416275970Scyimplosion at the original sender. 417275970ScyNote that, in order to avoid 418275970Scyaccidental or malicious disruption in this mode, both the server 419275970Scyand client should operate using symmetric\-key or public\-key 420275970Scyauthentication as described in 421275970Scy.Sx Authentication Options . 422275970Scy.It Ic multicastclient Ar address ... 423275970ScyThis command enables reception of multicast server messages to 424275970Scythe multicast group address(es) (type m) specified. 425275970ScyUpon receiving 426275970Scya message for the first time, the multicast client measures the 427275970Scynominal server propagation delay using a brief client/server 428275970Scyexchange with the server, then enters the broadcast client mode, in 429275970Scywhich it synchronizes to succeeding multicast messages. 430275970ScyNote that, 431275970Scyin order to avoid accidental or malicious disruption in this mode, 432275970Scyboth the server and client should operate using symmetric\-key or 433275970Scypublic\-key authentication as described in 434275970Scy.Sx Authentication Options . 435280849Scy.It Ic mdnstries Ar number 436280849ScyIf we are participating in mDNS, 437280849Scyafter we have synched for the first time 438280849Scywe attempt to register with the mDNS system. 439280849ScyIf that registration attempt fails, 440280849Scywe try again at one minute intervals for up to 441280849Scy.Ic mdnstries 442280849Scytimes. 443280849ScyAfter all, 444280849Scy.Ic ntpd 445280849Scymay be starting before mDNS. 446280849ScyThe default value for 447280849Scy.Ic mdnstries 448280849Scyis 5. 449275970Scy.El 450275970Scy.Sh Authentication Support 451275970ScyAuthentication support allows the NTP client to verify that the 452275970Scyserver is in fact known and trusted and not an intruder intending 453275970Scyaccidentally or on purpose to masquerade as that server. 454275970ScyThe NTPv3 455275970Scyspecification RFC\-1305 defines a scheme which provides 456275970Scycryptographic authentication of received NTP packets. 457275970ScyOriginally, 458275970Scythis was done using the Data Encryption Standard (DES) algorithm 459275970Scyoperating in Cipher Block Chaining (CBC) mode, commonly called 460275970ScyDES\-CBC. 461275970ScySubsequently, this was replaced by the RSA Message Digest 462275970Scy5 (MD5) algorithm using a private key, commonly called keyed\-MD5. 463275970ScyEither algorithm computes a message digest, or one\-way hash, which 464275970Scycan be used to verify the server has the correct private key and 465275970Scykey identifier. 466275970Scy.Pp 467275970ScyNTPv4 retains the NTPv3 scheme, properly described as symmetric key 468275970Scycryptography and, in addition, provides a new Autokey scheme 469275970Scybased on public key cryptography. 470275970ScyPublic key cryptography is generally considered more secure 471275970Scythan symmetric key cryptography, since the security is based 472275970Scyon a private value which is generated by each server and 473275970Scynever revealed. 474275970ScyWith Autokey all key distribution and 475275970Scymanagement functions involve only public values, which 476275970Scyconsiderably simplifies key distribution and storage. 477275970ScyPublic key management is based on X.509 certificates, 478275970Scywhich can be provided by commercial services or 479275970Scyproduced by utility programs in the OpenSSL software library 480275970Scyor the NTPv4 distribution. 481275970Scy.Pp 482275970ScyWhile the algorithms for symmetric key cryptography are 483275970Scyincluded in the NTPv4 distribution, public key cryptography 484275970Scyrequires the OpenSSL software library to be installed 485275970Scybefore building the NTP distribution. 486275970ScyDirections for doing that 487275970Scyare on the Building and Installing the Distribution page. 488275970Scy.Pp 489275970ScyAuthentication is configured separately for each association 490275970Scyusing the 491275970Scy.Cm key 492275970Scyor 493275970Scy.Cm autokey 494275970Scysubcommand on the 495275970Scy.Ic peer , 496275970Scy.Ic server , 497275970Scy.Ic broadcast 498275970Scyand 499275970Scy.Ic manycastclient 500275970Scyconfiguration commands as described in 501275970Scy.Sx Configuration Options 502275970Scypage. 503275970ScyThe authentication 504275970Scyoptions described below specify the locations of the key files, 505275970Scyif other than default, which symmetric keys are trusted 506275970Scyand the interval between various operations, if other than default. 507275970Scy.Pp 508275970ScyAuthentication is always enabled, 509275970Scyalthough ineffective if not configured as 510275970Scydescribed below. 511275970ScyIf a NTP packet arrives 512275970Scyincluding a message authentication 513275970Scycode (MAC), it is accepted only if it 514275970Scypasses all cryptographic checks. 515275970ScyThe 516275970Scychecks require correct key ID, key value 517275970Scyand message digest. 518275970ScyIf the packet has 519275970Scybeen modified in any way or replayed 520275970Scyby an intruder, it will fail one or more 521275970Scyof these checks and be discarded. 522275970ScyFurthermore, the Autokey scheme requires a 523275970Scypreliminary protocol exchange to obtain 524275970Scythe server certificate, verify its 525275970Scycredentials and initialize the protocol 526275970Scy.Pp 527275970ScyThe 528275970Scy.Cm auth 529275970Scyflag controls whether new associations or 530275970Scyremote configuration commands require cryptographic authentication. 531275970ScyThis flag can be set or reset by the 532275970Scy.Ic enable 533275970Scyand 534275970Scy.Ic disable 535275970Scycommands and also by remote 536275970Scyconfiguration commands sent by a 537275970Scy.Xr ntpdc 1ntpdcmdoc 538298770Sdelphijprogram running on 539275970Scyanother machine. 540275970ScyIf this flag is enabled, which is the default 541275970Scycase, new broadcast client and symmetric passive associations and 542275970Scyremote configuration commands must be cryptographically 543275970Scyauthenticated using either symmetric key or public key cryptography. 544275970ScyIf this 545275970Scyflag is disabled, these operations are effective 546275970Scyeven if not cryptographic 547275970Scyauthenticated. 548275970ScyIt should be understood 549275970Scythat operating with the 550275970Scy.Ic auth 551275970Scyflag disabled invites a significant vulnerability 552275970Scywhere a rogue hacker can 553275970Scymasquerade as a falseticker and seriously 554275970Scydisrupt system timekeeping. 555275970ScyIt is 556275970Scyimportant to note that this flag has no purpose 557275970Scyother than to allow or disallow 558275970Scya new association in response to new broadcast 559275970Scyand symmetric active messages 560275970Scyand remote configuration commands and, in particular, 561275970Scythe flag has no effect on 562275970Scythe authentication process itself. 563275970Scy.Pp 564275970ScyAn attractive alternative where multicast support is available 565275970Scyis manycast mode, in which clients periodically troll 566275970Scyfor servers as described in the 567275970Scy.Sx Automatic NTP Configuration Options 568275970Scypage. 569275970ScyEither symmetric key or public key 570275970Scycryptographic authentication can be used in this mode. 571275970ScyThe principle advantage 572275970Scyof manycast mode is that potential servers need not be 573275970Scyconfigured in advance, 574275970Scysince the client finds them during regular operation, 575275970Scyand the configuration 576275970Scyfiles for all clients can be identical. 577275970Scy.Pp 578275970ScyThe security model and protocol schemes for 579275970Scyboth symmetric key and public key 580275970Scycryptography are summarized below; 581275970Scyfurther details are in the briefings, papers 582275970Scyand reports at the NTP project page linked from 583275970Scy.Li http://www.ntp.org/ . 584275970Scy.Ss Symmetric\-Key Cryptography 585275970ScyThe original RFC\-1305 specification allows any one of possibly 586275970Scy65,534 keys, each distinguished by a 32\-bit key identifier, to 587275970Scyauthenticate an association. 588275970ScyThe servers and clients involved must 589275970Scyagree on the key and key identifier to 590275970Scyauthenticate NTP packets. 591275970ScyKeys and 592275970Scyrelated information are specified in a key 593275970Scyfile, usually called 594275970Scy.Pa ntp.keys , 595275970Scywhich must be distributed and stored using 596275970Scysecure means beyond the scope of the NTP protocol itself. 597275970ScyBesides the keys used 598275970Scyfor ordinary NTP associations, 599275970Scyadditional keys can be used as passwords for the 600275970Scy.Xr ntpq 1ntpqmdoc 601275970Scyand 602275970Scy.Xr ntpdc 1ntpdcmdoc 603275970Scyutility programs. 604275970Scy.Pp 605275970ScyWhen 606275970Scy.Xr ntpd 1ntpdmdoc 607275970Scyis first started, it reads the key file specified in the 608275970Scy.Ic keys 609275970Scyconfiguration command and installs the keys 610275970Scyin the key cache. 611275970ScyHowever, 612275970Scyindividual keys must be activated with the 613275970Scy.Ic trusted 614275970Scycommand before use. 615275970ScyThis 616275970Scyallows, for instance, the installation of possibly 617275970Scyseveral batches of keys and 618275970Scythen activating or deactivating each batch 619275970Scyremotely using 620275970Scy.Xr ntpdc 1ntpdcmdoc . 621275970ScyThis also provides a revocation capability that can be used 622275970Scyif a key becomes compromised. 623275970ScyThe 624275970Scy.Ic requestkey 625275970Scycommand selects the key used as the password for the 626275970Scy.Xr ntpdc 1ntpdcmdoc 627275970Scyutility, while the 628275970Scy.Ic controlkey 629275970Scycommand selects the key used as the password for the 630275970Scy.Xr ntpq 1ntpqmdoc 631275970Scyutility. 632275970Scy.Ss Public Key Cryptography 633275970ScyNTPv4 supports the original NTPv3 symmetric key scheme 634275970Scydescribed in RFC\-1305 and in addition the Autokey protocol, 635275970Scywhich is based on public key cryptography. 636275970ScyThe Autokey Version 2 protocol described on the Autokey Protocol 637275970Scypage verifies packet integrity using MD5 message digests 638275970Scyand verifies the source with digital signatures and any of several 639275970Scydigest/signature schemes. 640275970ScyOptional identity schemes described on the Identity Schemes 641275970Scypage and based on cryptographic challenge/response algorithms 642275970Scyare also available. 643275970ScyUsing all of these schemes provides strong security against 644275970Scyreplay with or without modification, spoofing, masquerade 645275970Scyand most forms of clogging attacks. 646275970Scy.\" .Pp 647275970Scy.\" The cryptographic means necessary for all Autokey operations 648275970Scy.\" is provided by the OpenSSL software library. 649275970Scy.\" This library is available from http://www.openssl.org/ 650275970Scy.\" and can be installed using the procedures outlined 651275970Scy.\" in the Building and Installing the Distribution page. 652275970Scy.\" Once installed, 653275970Scy.\" the configure and build 654275970Scy.\" process automatically detects the library and links 655275970Scy.\" the library routines required. 656275970Scy.Pp 657275970ScyThe Autokey protocol has several modes of operation 658275970Scycorresponding to the various NTP modes supported. 659275970ScyMost modes use a special cookie which can be 660275970Scycomputed independently by the client and server, 661275970Scybut encrypted in transmission. 662275970ScyAll modes use in addition a variant of the S\-KEY scheme, 663275970Scyin which a pseudo\-random key list is generated and used 664275970Scyin reverse order. 665275970ScyThese schemes are described along with an executive summary, 666275970Scycurrent status, briefing slides and reading list on the 667275970Scy.Sx Autonomous Authentication 668275970Scypage. 669275970Scy.Pp 670275970ScyThe specific cryptographic environment used by Autokey servers 671275970Scyand clients is determined by a set of files 672275970Scyand soft links generated by the 673275970Scy.Xr ntp\-keygen 1ntpkeygenmdoc 674275970Scyprogram. 675275970ScyThis includes a required host key file, 676275970Scyrequired certificate file and optional sign key file, 677275970Scyleapsecond file and identity scheme files. 678275970ScyThe 679275970Scydigest/signature scheme is specified in the X.509 certificate 680275970Scyalong with the matching sign key. 681275970ScyThere are several schemes 682275970Scyavailable in the OpenSSL software library, each identified 683275970Scyby a specific string such as 684275970Scy.Cm md5WithRSAEncryption , 685275970Scywhich stands for the MD5 message digest with RSA 686275970Scyencryption scheme. 687275970ScyThe current NTP distribution supports 688275970Scyall the schemes in the OpenSSL library, including 689275970Scythose based on RSA and DSA digital signatures. 690275970Scy.Pp 691275970ScyNTP secure groups can be used to define cryptographic compartments 692275970Scyand security hierarchies. 693275970ScyIt is important that every host 694275970Scyin the group be able to construct a certificate trail to one 695275970Scyor more trusted hosts in the same group. 696275970ScyEach group 697275970Scyhost runs the Autokey protocol to obtain the certificates 698275970Scyfor all hosts along the trail to one or more trusted hosts. 699275970ScyThis requires the configuration file in all hosts to be 700275970Scyengineered so that, even under anticipated failure conditions, 701275970Scythe NTP subnet will form such that every group host can find 702275970Scya trail to at least one trusted host. 703275970Scy.Ss Naming and Addressing 704275970ScyIt is important to note that Autokey does not use DNS to 705275970Scyresolve addresses, since DNS can't be completely trusted 706275970Scyuntil the name servers have synchronized clocks. 707275970ScyThe cryptographic name used by Autokey to bind the host identity 708275970Scycredentials and cryptographic values must be independent 709275970Scyof interface, network and any other naming convention. 710275970ScyThe name appears in the host certificate in either or both 711275970Scythe subject and issuer fields, so protection against 712275970ScyDNS compromise is essential. 713275970Scy.Pp 714275970ScyBy convention, the name of an Autokey host is the name returned 715275970Scyby the Unix 716275970Scy.Xr gethostname 2 717275970Scysystem call or equivalent in other systems. 718275970ScyBy the system design 719275970Scymodel, there are no provisions to allow alternate names or aliases. 720275970ScyHowever, this is not to say that DNS aliases, different names 721275970Scyfor each interface, etc., are constrained in any way. 722275970Scy.Pp 723275970ScyIt is also important to note that Autokey verifies authenticity 724275970Scyusing the host name, network address and public keys, 725275970Scyall of which are bound together by the protocol specifically 726275970Scyto deflect masquerade attacks. 727275970ScyFor this reason Autokey 728298770Sdelphijincludes the source and destination IP addresses in message digest 729275970Scycomputations and so the same addresses must be available 730275970Scyat both the server and client. 731275970ScyFor this reason operation 732275970Scywith network address translation schemes is not possible. 733275970ScyThis reflects the intended robust security model where government 734275970Scyand corporate NTP servers are operated outside firewall perimeters. 735275970Scy.Ss Operation 736275970ScyA specific combination of authentication scheme (none, 737275970Scysymmetric key, public key) and identity scheme is called 738275970Scya cryptotype, although not all combinations are compatible. 739275970ScyThere may be management configurations where the clients, 740275970Scyservers and peers may not all support the same cryptotypes. 741275970ScyA secure NTPv4 subnet can be configured in many ways while 742275970Scykeeping in mind the principles explained above and 743275970Scyin this section. 744275970ScyNote however that some cryptotype 745275970Scycombinations may successfully interoperate with each other, 746275970Scybut may not represent good security practice. 747275970Scy.Pp 748275970ScyThe cryptotype of an association is determined at the time 749275970Scyof mobilization, either at configuration time or some time 750275970Scylater when a message of appropriate cryptotype arrives. 751275970ScyWhen mobilized by a 752275970Scy.Ic server 753275970Scyor 754275970Scy.Ic peer 755275970Scyconfiguration command and no 756275970Scy.Ic key 757275970Scyor 758275970Scy.Ic autokey 759275970Scysubcommands are present, the association is not 760275970Scyauthenticated; if the 761275970Scy.Ic key 762275970Scysubcommand is present, the association is authenticated 763275970Scyusing the symmetric key ID specified; if the 764275970Scy.Ic autokey 765275970Scysubcommand is present, the association is authenticated 766275970Scyusing Autokey. 767275970Scy.Pp 768275970ScyWhen multiple identity schemes are supported in the Autokey 769275970Scyprotocol, the first message exchange determines which one is used. 770275970ScyThe client request message contains bits corresponding 771275970Scyto which schemes it has available. 772275970ScyThe server response message 773275970Scycontains bits corresponding to which schemes it has available. 774275970ScyBoth server and client match the received bits with their own 775275970Scyand select a common scheme. 776275970Scy.Pp 777275970ScyFollowing the principle that time is a public value, 778275970Scya server responds to any client packet that matches 779275970Scyits cryptotype capabilities. 780275970ScyThus, a server receiving 781275970Scyan unauthenticated packet will respond with an unauthenticated 782275970Scypacket, while the same server receiving a packet of a cryptotype 783275970Scyit supports will respond with packets of that cryptotype. 784275970ScyHowever, unconfigured broadcast or manycast client 785275970Scyassociations or symmetric passive associations will not be 786275970Scymobilized unless the server supports a cryptotype compatible 787275970Scywith the first packet received. 788275970ScyBy default, unauthenticated associations will not be mobilized 789275970Scyunless overridden in a decidedly dangerous way. 790275970Scy.Pp 791275970ScySome examples may help to reduce confusion. 792275970ScyClient Alice has no specific cryptotype selected. 793275970ScyServer Bob has both a symmetric key file and minimal Autokey files. 794275970ScyAlice's unauthenticated messages arrive at Bob, who replies with 795275970Scyunauthenticated messages. 796275970ScyCathy has a copy of Bob's symmetric 797275970Scykey file and has selected key ID 4 in messages to Bob. 798275970ScyBob verifies the message with his key ID 4. 799275970ScyIf it's the 800275970Scysame key and the message is verified, Bob sends Cathy a reply 801275970Scyauthenticated with that key. 802275970ScyIf verification fails, 803275970ScyBob sends Cathy a thing called a crypto\-NAK, which tells her 804275970Scysomething broke. 805275970ScyShe can see the evidence using the 806275970Scy.Xr ntpq 1ntpqmdoc 807275970Scyprogram. 808275970Scy.Pp 809275970ScyDenise has rolled her own host key and certificate. 810275970ScyShe also uses one of the identity schemes as Bob. 811275970ScyShe sends the first Autokey message to Bob and they 812275970Scyboth dance the protocol authentication and identity steps. 813275970ScyIf all comes out okay, Denise and Bob continue as described above. 814275970Scy.Pp 815275970ScyIt should be clear from the above that Bob can support 816275970Scyall the girls at the same time, as long as he has compatible 817275970Scyauthentication and identity credentials. 818275970ScyNow, Bob can act just like the girls in his own choice of servers; 819275970Scyhe can run multiple configured associations with multiple different 820275970Scyservers (or the same server, although that might not be useful). 821275970ScyBut, wise security policy might preclude some cryptotype 822275970Scycombinations; for instance, running an identity scheme 823275970Scywith one server and no authentication with another might not be wise. 824275970Scy.Ss Key Management 825275970ScyThe cryptographic values used by the Autokey protocol are 826275970Scyincorporated as a set of files generated by the 827275970Scy.Xr ntp\-keygen 1ntpkeygenmdoc 828275970Scyutility program, including symmetric key, host key and 829275970Scypublic certificate files, as well as sign key, identity parameters 830275970Scyand leapseconds files. 831275970ScyAlternatively, host and sign keys and 832275970Scycertificate files can be generated by the OpenSSL utilities 833275970Scyand certificates can be imported from public certificate 834275970Scyauthorities. 835275970ScyNote that symmetric keys are necessary for the 836275970Scy.Xr ntpq 1ntpqmdoc 837275970Scyand 838275970Scy.Xr ntpdc 1ntpdcmdoc 839275970Scyutility programs. 840275970ScyThe remaining files are necessary only for the 841275970ScyAutokey protocol. 842275970Scy.Pp 843275970ScyCertificates imported from OpenSSL or public certificate 844275970Scyauthorities have certian limitations. 845275970ScyThe certificate should be in ASN.1 syntax, X.509 Version 3 846275970Scyformat and encoded in PEM, which is the same format 847275970Scyused by OpenSSL. 848275970ScyThe overall length of the certificate encoded 849275970Scyin ASN.1 must not exceed 1024 bytes. 850275970ScyThe subject distinguished 851275970Scyname field (CN) is the fully qualified name of the host 852275970Scyon which it is used; the remaining subject fields are ignored. 853275970ScyThe certificate extension fields must not contain either 854275970Scya subject key identifier or a issuer key identifier field; 855275970Scyhowever, an extended key usage field for a trusted host must 856275970Scycontain the value 857275970Scy.Cm trustRoot ; . 858275970ScyOther extension fields are ignored. 859275970Scy.Ss Authentication Commands 860275970Scy.Bl -tag -width indent 861275970Scy.It Ic autokey Op Ar logsec 862275970ScySpecifies the interval between regenerations of the session key 863275970Scylist used with the Autokey protocol. 864275970ScyNote that the size of the key 865275970Scylist for each association depends on this interval and the current 866275970Scypoll interval. 867275970ScyThe default value is 12 (4096 s or about 1.1 hours). 868275970ScyFor poll intervals above the specified interval, a session key list 869275970Scywith a single entry will be regenerated for every message 870275970Scysent. 871275970Scy.It Ic controlkey Ar key 872275970ScySpecifies the key identifier to use with the 873275970Scy.Xr ntpq 1ntpqmdoc 874275970Scyutility, which uses the standard 875275970Scyprotocol defined in RFC\-1305. 876275970ScyThe 877275970Scy.Ar key 878275970Scyargument is 879275970Scythe key identifier for a trusted key, where the value can be in the 880275970Scyrange 1 to 65,534, inclusive. 881275970Scy.It Xo Ic crypto 882275970Scy.Op Cm cert Ar file 883275970Scy.Op Cm leap Ar file 884275970Scy.Op Cm randfile Ar file 885275970Scy.Op Cm host Ar file 886275970Scy.Op Cm sign Ar file 887275970Scy.Op Cm gq Ar file 888275970Scy.Op Cm gqpar Ar file 889275970Scy.Op Cm iffpar Ar file 890275970Scy.Op Cm mvpar Ar file 891275970Scy.Op Cm pw Ar password 892275970Scy.Xc 893275970ScyThis command requires the OpenSSL library. 894275970ScyIt activates public key 895275970Scycryptography, selects the message digest and signature 896275970Scyencryption scheme and loads the required private and public 897275970Scyvalues described above. 898275970ScyIf one or more files are left unspecified, 899275970Scythe default names are used as described above. 900275970ScyUnless the complete path and name of the file are specified, the 901275970Scylocation of a file is relative to the keys directory specified 902275970Scyin the 903275970Scy.Ic keysdir 904275970Scycommand or default 905275970Scy.Pa /usr/local/etc . 906275970ScyFollowing are the subcommands: 907275970Scy.Bl -tag -width indent 908275970Scy.It Cm cert Ar file 909275970ScySpecifies the location of the required host public certificate file. 910275970ScyThis overrides the link 911275970Scy.Pa ntpkey_cert_ Ns Ar hostname 912275970Scyin the keys directory. 913275970Scy.It Cm gqpar Ar file 914275970ScySpecifies the location of the optional GQ parameters file. 915275970ScyThis 916275970Scyoverrides the link 917275970Scy.Pa ntpkey_gq_ Ns Ar hostname 918275970Scyin the keys directory. 919275970Scy.It Cm host Ar file 920275970ScySpecifies the location of the required host key file. 921275970ScyThis overrides 922275970Scythe link 923275970Scy.Pa ntpkey_key_ Ns Ar hostname 924275970Scyin the keys directory. 925275970Scy.It Cm iffpar Ar file 926298770SdelphijSpecifies the location of the optional IFF parameters file. 927298770SdelphijThis overrides the link 928275970Scy.Pa ntpkey_iff_ Ns Ar hostname 929275970Scyin the keys directory. 930275970Scy.It Cm leap Ar file 931275970ScySpecifies the location of the optional leapsecond file. 932275970ScyThis overrides the link 933275970Scy.Pa ntpkey_leap 934275970Scyin the keys directory. 935275970Scy.It Cm mvpar Ar file 936275970ScySpecifies the location of the optional MV parameters file. 937298770SdelphijThis overrides the link 938275970Scy.Pa ntpkey_mv_ Ns Ar hostname 939275970Scyin the keys directory. 940275970Scy.It Cm pw Ar password 941275970ScySpecifies the password to decrypt files containing private keys and 942275970Scyidentity parameters. 943275970ScyThis is required only if these files have been 944275970Scyencrypted. 945275970Scy.It Cm randfile Ar file 946275970ScySpecifies the location of the random seed file used by the OpenSSL 947275970Scylibrary. 948275970ScyThe defaults are described in the main text above. 949275970Scy.It Cm sign Ar file 950275970ScySpecifies the location of the optional sign key file. 951275970ScyThis overrides 952275970Scythe link 953275970Scy.Pa ntpkey_sign_ Ns Ar hostname 954275970Scyin the keys directory. 955275970ScyIf this file is 956275970Scynot found, the host key is also the sign key. 957275970Scy.El 958275970Scy.It Ic keys Ar keyfile 959275970ScySpecifies the complete path and location of the MD5 key file 960275970Scycontaining the keys and key identifiers used by 961275970Scy.Xr ntpd 1ntpdmdoc , 962275970Scy.Xr ntpq 1ntpqmdoc 963275970Scyand 964275970Scy.Xr ntpdc 1ntpdcmdoc 965275970Scywhen operating with symmetric key cryptography. 966275970ScyThis is the same operation as the 967275970Scy.Fl k 968275970Scycommand line option. 969275970Scy.It Ic keysdir Ar path 970275970ScyThis command specifies the default directory path for 971275970Scycryptographic keys, parameters and certificates. 972275970ScyThe default is 973275970Scy.Pa /usr/local/etc/ . 974275970Scy.It Ic requestkey Ar key 975275970ScySpecifies the key identifier to use with the 976275970Scy.Xr ntpdc 1ntpdcmdoc 977275970Scyutility program, which uses a 978275970Scyproprietary protocol specific to this implementation of 979275970Scy.Xr ntpd 1ntpdmdoc . 980275970ScyThe 981275970Scy.Ar key 982275970Scyargument is a key identifier 983275970Scyfor the trusted key, where the value can be in the range 1 to 984275970Scy65,534, inclusive. 985275970Scy.It Ic revoke Ar logsec 986275970ScySpecifies the interval between re\-randomization of certain 987275970Scycryptographic values used by the Autokey scheme, as a power of 2 in 988275970Scyseconds. 989275970ScyThese values need to be updated frequently in order to 990275970Scydeflect brute\-force attacks on the algorithms of the scheme; 991275970Scyhowever, updating some values is a relatively expensive operation. 992275970ScyThe default interval is 16 (65,536 s or about 18 hours). 993275970ScyFor poll 994275970Scyintervals above the specified interval, the values will be updated 995275970Scyfor every message sent. 996275970Scy.It Ic trustedkey Ar key ... 997275970ScySpecifies the key identifiers which are trusted for the 998275970Scypurposes of authenticating peers with symmetric key cryptography, 999275970Scyas well as keys used by the 1000275970Scy.Xr ntpq 1ntpqmdoc 1001275970Scyand 1002275970Scy.Xr ntpdc 1ntpdcmdoc 1003275970Scyprograms. 1004275970ScyThe authentication procedures require that both the local 1005275970Scyand remote servers share the same key and key identifier for this 1006275970Scypurpose, although different keys can be used with different 1007275970Scyservers. 1008275970ScyThe 1009275970Scy.Ar key 1010275970Scyarguments are 32\-bit unsigned 1011275970Scyintegers with values from 1 to 65,534. 1012275970Scy.El 1013275970Scy.Ss Error Codes 1014275970ScyThe following error codes are reported via the NTP control 1015275970Scyand monitoring protocol trap mechanism. 1016275970Scy.Bl -tag -width indent 1017275970Scy.It 101 1018275970Scy.Pq bad field format or length 1019275970ScyThe packet has invalid version, length or format. 1020275970Scy.It 102 1021275970Scy.Pq bad timestamp 1022275970ScyThe packet timestamp is the same or older than the most recent received. 1023275970ScyThis could be due to a replay or a server clock time step. 1024275970Scy.It 103 1025275970Scy.Pq bad filestamp 1026275970ScyThe packet filestamp is the same or older than the most recent received. 1027275970ScyThis could be due to a replay or a key file generation error. 1028275970Scy.It 104 1029275970Scy.Pq bad or missing public key 1030275970ScyThe public key is missing, has incorrect format or is an unsupported type. 1031275970Scy.It 105 1032275970Scy.Pq unsupported digest type 1033275970ScyThe server requires an unsupported digest/signature scheme. 1034275970Scy.It 106 1035275970Scy.Pq mismatched digest types 1036275970ScyNot used. 1037275970Scy.It 107 1038275970Scy.Pq bad signature length 1039275970ScyThe signature length does not match the current public key. 1040275970Scy.It 108 1041275970Scy.Pq signature not verified 1042275970ScyThe message fails the signature check. 1043275970ScyIt could be bogus or signed by a 1044275970Scydifferent private key. 1045275970Scy.It 109 1046275970Scy.Pq certificate not verified 1047275970ScyThe certificate is invalid or signed with the wrong key. 1048275970Scy.It 110 1049275970Scy.Pq certificate not verified 1050275970ScyThe certificate is not yet valid or has expired or the signature could not 1051275970Scybe verified. 1052275970Scy.It 111 1053275970Scy.Pq bad or missing cookie 1054275970ScyThe cookie is missing, corrupted or bogus. 1055275970Scy.It 112 1056275970Scy.Pq bad or missing leapseconds table 1057275970ScyThe leapseconds table is missing, corrupted or bogus. 1058275970Scy.It 113 1059275970Scy.Pq bad or missing certificate 1060275970ScyThe certificate is missing, corrupted or bogus. 1061275970Scy.It 114 1062275970Scy.Pq bad or missing identity 1063275970ScyThe identity key is missing, corrupt or bogus. 1064275970Scy.El 1065275970Scy.Sh Monitoring Support 1066275970Scy.Xr ntpd 1ntpdmdoc 1067275970Scyincludes a comprehensive monitoring facility suitable 1068275970Scyfor continuous, long term recording of server and client 1069275970Scytimekeeping performance. 1070275970ScySee the 1071275970Scy.Ic statistics 1072275970Scycommand below 1073275970Scyfor a listing and example of each type of statistics currently 1074275970Scysupported. 1075275970ScyStatistic files are managed using file generation sets 1076275970Scyand scripts in the 1077275970Scy.Pa ./scripts 1078298770Sdelphijdirectory of the source code distribution. 1079275970ScyUsing 1080275970Scythese facilities and 1081275970Scy.Ux 1082275970Scy.Xr cron 8 1083275970Scyjobs, the data can be 1084275970Scyautomatically summarized and archived for retrospective analysis. 1085275970Scy.Ss Monitoring Commands 1086275970Scy.Bl -tag -width indent 1087275970Scy.It Ic statistics Ar name ... 1088275970ScyEnables writing of statistics records. 1089275970ScyCurrently, eight kinds of 1090275970Scy.Ar name 1091275970Scystatistics are supported. 1092275970Scy.Bl -tag -width indent 1093275970Scy.It Cm clockstats 1094275970ScyEnables recording of clock driver statistics information. 1095275970ScyEach update 1096275970Scyreceived from a clock driver appends a line of the following form to 1097275970Scythe file generation set named 1098275970Scy.Cm clockstats : 1099275970Scy.Bd -literal 1100275970Scy49213 525.624 127.127.4.1 93 226 00:08:29.606 D 1101275970Scy.Ed 1102275970Scy.Pp 1103275970ScyThe first two fields show the date (Modified Julian Day) and time 1104275970Scy(seconds and fraction past UTC midnight). 1105275970ScyThe next field shows the 1106275970Scyclock address in dotted\-quad notation. 1107275970ScyThe final field shows the last 1108275970Scytimecode received from the clock in decoded ASCII format, where 1109275970Scymeaningful. 1110275970ScyIn some clock drivers a good deal of additional information 1111275970Scycan be gathered and displayed as well. 1112275970ScySee information specific to each 1113275970Scyclock for further details. 1114275970Scy.It Cm cryptostats 1115275970ScyThis option requires the OpenSSL cryptographic software library. 1116275970ScyIt 1117275970Scyenables recording of cryptographic public key protocol information. 1118275970ScyEach message received by the protocol module appends a line of the 1119275970Scyfollowing form to the file generation set named 1120275970Scy.Cm cryptostats : 1121275970Scy.Bd -literal 1122275970Scy49213 525.624 127.127.4.1 message 1123275970Scy.Ed 1124275970Scy.Pp 1125275970ScyThe first two fields show the date (Modified Julian Day) and time 1126275970Scy(seconds and fraction past UTC midnight). 1127275970ScyThe next field shows the peer 1128275970Scyaddress in dotted\-quad notation, The final message field includes the 1129275970Scymessage type and certain ancillary information. 1130275970ScySee the 1131275970Scy.Sx Authentication Options 1132275970Scysection for further information. 1133275970Scy.It Cm loopstats 1134275970ScyEnables recording of loop filter statistics information. 1135275970ScyEach 1136275970Scyupdate of the local clock outputs a line of the following form to 1137275970Scythe file generation set named 1138275970Scy.Cm loopstats : 1139275970Scy.Bd -literal 1140275970Scy50935 75440.031 0.000006019 13.778190 0.000351733 0.0133806 1141275970Scy.Ed 1142275970Scy.Pp 1143275970ScyThe first two fields show the date (Modified Julian Day) and 1144275970Scytime (seconds and fraction past UTC midnight). 1145275970ScyThe next five fields 1146275970Scyshow time offset (seconds), frequency offset (parts per million \- 1147275970ScyPPM), RMS jitter (seconds), Allan deviation (PPM) and clock 1148275970Scydiscipline time constant. 1149275970Scy.It Cm peerstats 1150275970ScyEnables recording of peer statistics information. 1151275970ScyThis includes 1152275970Scystatistics records of all peers of a NTP server and of special 1153275970Scysignals, where present and configured. 1154275970ScyEach valid update appends a 1155275970Scyline of the following form to the current element of a file 1156275970Scygeneration set named 1157275970Scy.Cm peerstats : 1158275970Scy.Bd -literal 1159275970Scy48773 10847.650 127.127.4.1 9714 \-0.001605376 0.000000000 0.001424877 0.000958674 1160275970Scy.Ed 1161275970Scy.Pp 1162275970ScyThe first two fields show the date (Modified Julian Day) and 1163275970Scytime (seconds and fraction past UTC midnight). 1164275970ScyThe next two fields 1165275970Scyshow the peer address in dotted\-quad notation and status, 1166275970Scyrespectively. 1167275970ScyThe status field is encoded in hex in the format 1168275970Scydescribed in Appendix A of the NTP specification RFC 1305. 1169275970ScyThe final four fields show the offset, 1170275970Scydelay, dispersion and RMS jitter, all in seconds. 1171275970Scy.It Cm rawstats 1172275970ScyEnables recording of raw\-timestamp statistics information. 1173275970ScyThis 1174275970Scyincludes statistics records of all peers of a NTP server and of 1175275970Scyspecial signals, where present and configured. 1176275970ScyEach NTP message 1177275970Scyreceived from a peer or clock driver appends a line of the 1178275970Scyfollowing form to the file generation set named 1179275970Scy.Cm rawstats : 1180275970Scy.Bd -literal 1181275970Scy50928 2132.543 128.4.1.1 128.4.1.20 3102453281.584327000 3102453281.58622800031 02453332.540806000 3102453332.541458000 1182275970Scy.Ed 1183275970Scy.Pp 1184275970ScyThe first two fields show the date (Modified Julian Day) and 1185275970Scytime (seconds and fraction past UTC midnight). 1186275970ScyThe next two fields 1187275970Scyshow the remote peer or clock address followed by the local address 1188275970Scyin dotted\-quad notation. 1189275970ScyThe final four fields show the originate, 1190275970Scyreceive, transmit and final NTP timestamps in order. 1191275970ScyThe timestamp 1192275970Scyvalues are as received and before processing by the various data 1193275970Scysmoothing and mitigation algorithms. 1194275970Scy.It Cm sysstats 1195275970ScyEnables recording of ntpd statistics counters on a periodic basis. 1196275970ScyEach 1197275970Scyhour a line of the following form is appended to the file generation 1198275970Scyset named 1199275970Scy.Cm sysstats : 1200275970Scy.Bd -literal 1201275970Scy50928 2132.543 36000 81965 0 9546 56 71793 512 540 10 147 1202275970Scy.Ed 1203275970Scy.Pp 1204275970ScyThe first two fields show the date (Modified Julian Day) and time 1205275970Scy(seconds and fraction past UTC midnight). 1206275970ScyThe remaining ten fields show 1207275970Scythe statistics counter values accumulated since the last generated 1208275970Scyline. 1209275970Scy.Bl -tag -width indent 1210275970Scy.It Time since restart Cm 36000 1211275970ScyTime in hours since the system was last rebooted. 1212275970Scy.It Packets received Cm 81965 1213275970ScyTotal number of packets received. 1214275970Scy.It Packets processed Cm 0 1215275970ScyNumber of packets received in response to previous packets sent 1216275970Scy.It Current version Cm 9546 1217275970ScyNumber of packets matching the current NTP version. 1218275970Scy.It Previous version Cm 56 1219275970ScyNumber of packets matching the previous NTP version. 1220275970Scy.It Bad version Cm 71793 1221275970ScyNumber of packets matching neither NTP version. 1222275970Scy.It Access denied Cm 512 1223275970ScyNumber of packets denied access for any reason. 1224275970Scy.It Bad length or format Cm 540 1225275970ScyNumber of packets with invalid length, format or port number. 1226275970Scy.It Bad authentication Cm 10 1227275970ScyNumber of packets not verified as authentic. 1228275970Scy.It Rate exceeded Cm 147 1229275970ScyNumber of packets discarded due to rate limitation. 1230275970Scy.El 1231275970Scy.It Cm statsdir Ar directory_path 1232275970ScyIndicates the full path of a directory where statistics files 1233275970Scyshould be created (see below). 1234275970ScyThis keyword allows 1235275970Scythe (otherwise constant) 1236275970Scy.Cm filegen 1237275970Scyfilename prefix to be modified for file generation sets, which 1238275970Scyis useful for handling statistics logs. 1239275970Scy.It Cm filegen Ar name Xo 1240275970Scy.Op Cm file Ar filename 1241275970Scy.Op Cm type Ar typename 1242275970Scy.Op Cm link | nolink 1243275970Scy.Op Cm enable | disable 1244275970Scy.Xc 1245275970ScyConfigures setting of generation file set name. 1246275970ScyGeneration 1247275970Scyfile sets provide a means for handling files that are 1248275970Scycontinuously growing during the lifetime of a server. 1249275970ScyServer statistics are a typical example for such files. 1250275970ScyGeneration file sets provide access to a set of files used 1251275970Scyto store the actual data. 1252275970ScyAt any time at most one element 1253275970Scyof the set is being written to. 1254275970ScyThe type given specifies 1255275970Scywhen and how data will be directed to a new element of the set. 1256275970ScyThis way, information stored in elements of a file set 1257275970Scythat are currently unused are available for administrational 1258275970Scyoperations without the risk of disturbing the operation of ntpd. 1259275970Scy(Most important: they can be removed to free space for new data 1260275970Scyproduced.) 1261275970Scy.Pp 1262275970ScyNote that this command can be sent from the 1263275970Scy.Xr ntpdc 1ntpdcmdoc 1264275970Scyprogram running at a remote location. 1265275970Scy.Bl -tag -width indent 1266275970Scy.It Cm name 1267275970ScyThis is the type of the statistics records, as shown in the 1268275970Scy.Cm statistics 1269275970Scycommand. 1270275970Scy.It Cm file Ar filename 1271275970ScyThis is the file name for the statistics records. 1272275970ScyFilenames of set 1273275970Scymembers are built from three concatenated elements 1274275970Scy.Ar Cm prefix , 1275275970Scy.Ar Cm filename 1276275970Scyand 1277275970Scy.Ar Cm suffix : 1278275970Scy.Bl -tag -width indent 1279275970Scy.It Cm prefix 1280275970ScyThis is a constant filename path. 1281275970ScyIt is not subject to 1282275970Scymodifications via the 1283275970Scy.Ar filegen 1284275970Scyoption. 1285275970ScyIt is defined by the 1286275970Scyserver, usually specified as a compile\-time constant. 1287275970ScyIt may, 1288275970Scyhowever, be configurable for individual file generation sets 1289275970Scyvia other commands. 1290275970ScyFor example, the prefix used with 1291275970Scy.Ar loopstats 1292275970Scyand 1293275970Scy.Ar peerstats 1294275970Scygeneration can be configured using the 1295275970Scy.Ar statsdir 1296275970Scyoption explained above. 1297275970Scy.It Cm filename 1298275970ScyThis string is directly concatenated to the prefix mentioned 1299275970Scyabove (no intervening 1300275970Scy.Ql / ) . 1301275970ScyThis can be modified using 1302275970Scythe file argument to the 1303275970Scy.Ar filegen 1304275970Scystatement. 1305275970ScyNo 1306275970Scy.Pa .. 1307275970Scyelements are 1308275970Scyallowed in this component to prevent filenames referring to 1309275970Scyparts outside the filesystem hierarchy denoted by 1310275970Scy.Ar prefix . 1311275970Scy.It Cm suffix 1312275970ScyThis part is reflects individual elements of a file set. 1313275970ScyIt is 1314275970Scygenerated according to the type of a file set. 1315275970Scy.El 1316275970Scy.It Cm type Ar typename 1317275970ScyA file generation set is characterized by its type. 1318275970ScyThe following 1319275970Scytypes are supported: 1320275970Scy.Bl -tag -width indent 1321275970Scy.It Cm none 1322275970ScyThe file set is actually a single plain file. 1323275970Scy.It Cm pid 1324275970ScyOne element of file set is used per incarnation of a ntpd 1325275970Scyserver. 1326275970ScyThis type does not perform any changes to file set 1327275970Scymembers during runtime, however it provides an easy way of 1328275970Scyseparating files belonging to different 1329275970Scy.Xr ntpd 1ntpdmdoc 1330275970Scyserver incarnations. 1331275970ScyThe set member filename is built by appending a 1332275970Scy.Ql \&. 1333275970Scyto concatenated 1334275970Scy.Ar prefix 1335275970Scyand 1336275970Scy.Ar filename 1337275970Scystrings, and 1338275970Scyappending the decimal representation of the process ID of the 1339275970Scy.Xr ntpd 1ntpdmdoc 1340275970Scyserver process. 1341275970Scy.It Cm day 1342275970ScyOne file generation set element is created per day. 1343275970ScyA day is 1344275970Scydefined as the period between 00:00 and 24:00 UTC. 1345275970ScyThe file set 1346275970Scymember suffix consists of a 1347275970Scy.Ql \&. 1348275970Scyand a day specification in 1349275970Scythe form 1350275970Scy.Cm YYYYMMdd . 1351275970Scy.Cm YYYY 1352275970Scyis a 4\-digit year number (e.g., 1992). 1353275970Scy.Cm MM 1354275970Scyis a two digit month number. 1355275970Scy.Cm dd 1356275970Scyis a two digit day number. 1357275970ScyThus, all information written at 10 December 1992 would end up 1358275970Scyin a file named 1359275970Scy.Ar prefix 1360275970Scy.Ar filename Ns .19921210 . 1361275970Scy.It Cm week 1362275970ScyAny file set member contains data related to a certain week of 1363275970Scya year. 1364275970ScyThe term week is defined by computing day\-of\-year 1365275970Scymodulo 7. 1366275970ScyElements of such a file generation set are 1367275970Scydistinguished by appending the following suffix to the file set 1368275970Scyfilename base: A dot, a 4\-digit year number, the letter 1369275970Scy.Cm W , 1370275970Scyand a 2\-digit week number. 1371275970ScyFor example, information from January, 1372275970Scy10th 1992 would end up in a file with suffix 1373275970Scy.No . Ns Ar 1992W1 . 1374275970Scy.It Cm month 1375275970ScyOne generation file set element is generated per month. 1376275970ScyThe 1377275970Scyfile name suffix consists of a dot, a 4\-digit year number, and 1378275970Scya 2\-digit month. 1379275970Scy.It Cm year 1380275970ScyOne generation file element is generated per year. 1381275970ScyThe filename 1382275970Scysuffix consists of a dot and a 4 digit year number. 1383275970Scy.It Cm age 1384275970ScyThis type of file generation sets changes to a new element of 1385275970Scythe file set every 24 hours of server operation. 1386275970ScyThe filename 1387275970Scysuffix consists of a dot, the letter 1388275970Scy.Cm a , 1389275970Scyand an 8\-digit number. 1390275970ScyThis number is taken to be the number of seconds the server is 1391275970Scyrunning at the start of the corresponding 24\-hour period. 1392275970ScyInformation is only written to a file generation by specifying 1393275970Scy.Cm enable ; 1394275970Scyoutput is prevented by specifying 1395275970Scy.Cm disable . 1396275970Scy.El 1397275970Scy.It Cm link | nolink 1398275970ScyIt is convenient to be able to access the current element of a file 1399275970Scygeneration set by a fixed name. 1400275970ScyThis feature is enabled by 1401275970Scyspecifying 1402275970Scy.Cm link 1403275970Scyand disabled using 1404275970Scy.Cm nolink . 1405275970ScyIf link is specified, a 1406275970Scyhard link from the current file set element to a file without 1407275970Scysuffix is created. 1408275970ScyWhen there is already a file with this name and 1409275970Scythe number of links of this file is one, it is renamed appending a 1410275970Scydot, the letter 1411275970Scy.Cm C , 1412298770Sdelphijand the pid of the 1413298770Sdelphij.Xr ntpd 1ntpdmdoc 1414298770Sdelphijserver process. 1415275970ScyWhen the 1416275970Scynumber of links is greater than one, the file is unlinked. 1417275970ScyThis 1418275970Scyallows the current file to be accessed by a constant name. 1419275970Scy.It Cm enable \&| Cm disable 1420275970ScyEnables or disables the recording function. 1421275970Scy.El 1422275970Scy.El 1423275970Scy.El 1424275970Scy.Sh Access Control Support 1425275970ScyThe 1426275970Scy.Xr ntpd 1ntpdmdoc 1427275970Scydaemon implements a general purpose address/mask based restriction 1428275970Scylist. 1429275970ScyThe list contains address/match entries sorted first 1430275970Scyby increasing address values and and then by increasing mask values. 1431275970ScyA match occurs when the bitwise AND of the mask and the packet 1432275970Scysource address is equal to the bitwise AND of the mask and 1433275970Scyaddress in the list. 1434275970ScyThe list is searched in order with the 1435275970Scylast match found defining the restriction flags associated 1436275970Scywith the entry. 1437275970ScyAdditional information and examples can be found in the 1438275970Scy.Qq Notes on Configuring NTP and Setting up a NTP Subnet 1439275970Scypage 1440275970Scy(available as part of the HTML documentation 1441275970Scyprovided in 1442275970Scy.Pa /usr/share/doc/ntp ) . 1443275970Scy.Pp 1444275970ScyThe restriction facility was implemented in conformance 1445275970Scywith the access policies for the original NSFnet backbone 1446275970Scytime servers. 1447275970ScyLater the facility was expanded to deflect 1448275970Scycryptographic and clogging attacks. 1449275970ScyWhile this facility may 1450275970Scybe useful for keeping unwanted or broken or malicious clients 1451275970Scyfrom congesting innocent servers, it should not be considered 1452275970Scyan alternative to the NTP authentication facilities. 1453275970ScySource address based restrictions are easily circumvented 1454275970Scyby a determined cracker. 1455275970Scy.Pp 1456275970ScyClients can be denied service because they are explicitly 1457298770Sdelphijincluded in the restrict list created by the 1458298770Sdelphij.Ic restrict 1459298770Sdelphijcommand 1460275970Scyor implicitly as the result of cryptographic or rate limit 1461275970Scyviolations. 1462275970ScyCryptographic violations include certificate 1463275970Scyor identity verification failure; rate limit violations generally 1464275970Scyresult from defective NTP implementations that send packets 1465275970Scyat abusive rates. 1466275970ScySome violations cause denied service 1467275970Scyonly for the offending packet, others cause denied service 1468275970Scyfor a timed period and others cause the denied service for 1469298770Sdelphijan indefinite period. 1470275970ScyWhen a client or network is denied access 1471298770Sdelphijfor an indefinite period, the only way at present to remove 1472275970Scythe restrictions is by restarting the server. 1473275970Scy.Ss The Kiss\-of\-Death Packet 1474275970ScyOrdinarily, packets denied service are simply dropped with no 1475275970Scyfurther action except incrementing statistics counters. 1476275970ScySometimes a 1477275970Scymore proactive response is needed, such as a server message that 1478275970Scyexplicitly requests the client to stop sending and leave a message 1479275970Scyfor the system operator. 1480275970ScyA special packet format has been created 1481275970Scyfor this purpose called the "kiss\-of\-death" (KoD) packet. 1482275970ScyKoD packets have the leap bits set unsynchronized and stratum set 1483275970Scyto zero and the reference identifier field set to a four\-byte 1484275970ScyASCII code. 1485275970ScyIf the 1486275970Scy.Cm noserve 1487275970Scyor 1488275970Scy.Cm notrust 1489275970Scyflag of the matching restrict list entry is set, 1490275970Scythe code is "DENY"; if the 1491275970Scy.Cm limited 1492275970Scyflag is set and the rate limit 1493275970Scyis exceeded, the code is "RATE". 1494275970ScyFinally, if a cryptographic violation occurs, the code is "CRYP". 1495275970Scy.Pp 1496275970ScyA client receiving a KoD performs a set of sanity checks to 1497275970Scyminimize security exposure, then updates the stratum and 1498275970Scyreference identifier peer variables, sets the access 1499275970Scydenied (TEST4) bit in the peer flash variable and sends 1500275970Scya message to the log. 1501275970ScyAs long as the TEST4 bit is set, 1502275970Scythe client will send no further packets to the server. 1503275970ScyThe only way at present to recover from this condition is 1504275970Scyto restart the protocol at both the client and server. 1505275970ScyThis 1506275970Scyhappens automatically at the client when the association times out. 1507275970ScyIt will happen at the server only if the server operator cooperates. 1508275970Scy.Ss Access Control Commands 1509275970Scy.Bl -tag -width indent 1510275970Scy.It Xo Ic discard 1511275970Scy.Op Cm average Ar avg 1512275970Scy.Op Cm minimum Ar min 1513275970Scy.Op Cm monitor Ar prob 1514275970Scy.Xc 1515275970ScySet the parameters of the 1516275970Scy.Cm limited 1517275970Scyfacility which protects the server from 1518275970Scyclient abuse. 1519275970ScyThe 1520275970Scy.Cm average 1521275970Scysubcommand specifies the minimum average packet 1522275970Scyspacing, while the 1523275970Scy.Cm minimum 1524275970Scysubcommand specifies the minimum packet spacing. 1525275970ScyPackets that violate these minima are discarded 1526275970Scyand a kiss\-o'\-death packet returned if enabled. 1527275970ScyThe default 1528275970Scyminimum average and minimum are 5 and 2, respectively. 1529298770SdelphijThe 1530298770Sdelphij.Ic monitor 1531298770Sdelphijsubcommand specifies the probability of discard 1532275970Scyfor packets that overflow the rate\-control window. 1533275970Scy.It Xo Ic restrict address 1534275970Scy.Op Cm mask Ar mask 1535275970Scy.Op Ar flag ... 1536275970Scy.Xc 1537275970ScyThe 1538275970Scy.Ar address 1539275970Scyargument expressed in 1540275970Scydotted\-quad form is the address of a host or network. 1541275970ScyAlternatively, the 1542275970Scy.Ar address 1543275970Scyargument can be a valid host DNS name. 1544275970ScyThe 1545275970Scy.Ar mask 1546275970Scyargument expressed in dotted\-quad form defaults to 1547275970Scy.Cm 255.255.255.255 , 1548275970Scymeaning that the 1549275970Scy.Ar address 1550275970Scyis treated as the address of an individual host. 1551275970ScyA default entry (address 1552275970Scy.Cm 0.0.0.0 , 1553275970Scymask 1554275970Scy.Cm 0.0.0.0 ) 1555275970Scyis always included and is always the first entry in the list. 1556275970ScyNote that text string 1557275970Scy.Cm default , 1558275970Scywith no mask option, may 1559275970Scybe used to indicate the default entry. 1560275970ScyIn the current implementation, 1561275970Scy.Cm flag 1562275970Scyalways 1563275970Scyrestricts access, i.e., an entry with no flags indicates that free 1564275970Scyaccess to the server is to be given. 1565275970ScyThe flags are not orthogonal, 1566275970Scyin that more restrictive flags will often make less restrictive 1567275970Scyones redundant. 1568275970ScyThe flags can generally be classed into two 1569275970Scycategories, those which restrict time service and those which 1570275970Scyrestrict informational queries and attempts to do run\-time 1571275970Scyreconfiguration of the server. 1572275970ScyOne or more of the following flags 1573275970Scymay be specified: 1574275970Scy.Bl -tag -width indent 1575275970Scy.It Cm ignore 1576275970ScyDeny packets of all kinds, including 1577275970Scy.Xr ntpq 1ntpqmdoc 1578275970Scyand 1579275970Scy.Xr ntpdc 1ntpdcmdoc 1580275970Scyqueries. 1581275970Scy.It Cm kod 1582275970ScyIf this flag is set when an access violation occurs, a kiss\-o'\-death 1583275970Scy(KoD) packet is sent. 1584275970ScyKoD packets are rate limited to no more than one 1585275970Scyper second. 1586275970ScyIf another KoD packet occurs within one second after the 1587275970Scylast one, the packet is dropped. 1588275970Scy.It Cm limited 1589275970ScyDeny service if the packet spacing violates the lower limits specified 1590298770Sdelphijin the 1591298770Sdelphij.Ic discard 1592298770Sdelphijcommand. 1593275970ScyA history of clients is kept using the 1594275970Scymonitoring capability of 1595275970Scy.Xr ntpd 1ntpdmdoc . 1596275970ScyThus, monitoring is always active as 1597275970Scylong as there is a restriction entry with the 1598275970Scy.Cm limited 1599275970Scyflag. 1600275970Scy.It Cm lowpriotrap 1601275970ScyDeclare traps set by matching hosts to be low priority. 1602275970ScyThe 1603275970Scynumber of traps a server can maintain is limited (the current limit 1604275970Scyis 3). 1605275970ScyTraps are usually assigned on a first come, first served 1606275970Scybasis, with later trap requestors being denied service. 1607275970ScyThis flag 1608275970Scymodifies the assignment algorithm by allowing low priority traps to 1609275970Scybe overridden by later requests for normal priority traps. 1610275970Scy.It Cm nomodify 1611275970ScyDeny 1612275970Scy.Xr ntpq 1ntpqmdoc 1613275970Scyand 1614275970Scy.Xr ntpdc 1ntpdcmdoc 1615275970Scyqueries which attempt to modify the state of the 1616275970Scyserver (i.e., run time reconfiguration). 1617275970ScyQueries which return 1618275970Scyinformation are permitted. 1619275970Scy.It Cm noquery 1620275970ScyDeny 1621275970Scy.Xr ntpq 1ntpqmdoc 1622275970Scyand 1623275970Scy.Xr ntpdc 1ntpdcmdoc 1624275970Scyqueries. 1625275970ScyTime service is not affected. 1626275970Scy.It Cm nopeer 1627275970ScyDeny packets which would result in mobilizing a new association. 1628275970ScyThis 1629275970Scyincludes broadcast and symmetric active packets when a configured 1630275970Scyassociation does not exist. 1631275970ScyIt also includes 1632275970Scy.Cm pool 1633275970Scyassociations, so if you want to use servers from a 1634275970Scy.Cm pool 1635275970Scydirective and also want to use 1636275970Scy.Cm nopeer 1637275970Scyby default, you'll want a 1638275970Scy.Cm "restrict source ..." line as well that does 1639275970Scy.It not 1640275970Scyinclude the 1641275970Scy.Cm nopeer 1642275970Scydirective. 1643275970Scy.It Cm noserve 1644275970ScyDeny all packets except 1645275970Scy.Xr ntpq 1ntpqmdoc 1646275970Scyand 1647275970Scy.Xr ntpdc 1ntpdcmdoc 1648275970Scyqueries. 1649275970Scy.It Cm notrap 1650275970ScyDecline to provide mode 6 control message trap service to matching 1651275970Scyhosts. 1652298770SdelphijThe trap service is a subsystem of the 1653298770Sdelphij.Xr ntpq 1ntpqmdoc 1654298770Sdelphijcontrol message 1655275970Scyprotocol which is intended for use by remote event logging programs. 1656275970Scy.It Cm notrust 1657275970ScyDeny service unless the packet is cryptographically authenticated. 1658275970Scy.It Cm ntpport 1659275970ScyThis is actually a match algorithm modifier, rather than a 1660275970Scyrestriction flag. 1661275970ScyIts presence causes the restriction entry to be 1662275970Scymatched only if the source port in the packet is the standard NTP 1663275970ScyUDP port (123). 1664275970ScyBoth 1665275970Scy.Cm ntpport 1666275970Scyand 1667275970Scy.Cm non\-ntpport 1668275970Scymay 1669275970Scybe specified. 1670275970ScyThe 1671275970Scy.Cm ntpport 1672275970Scyis considered more specific and 1673275970Scyis sorted later in the list. 1674275970Scy.It Cm version 1675275970ScyDeny packets that do not match the current NTP version. 1676275970Scy.El 1677275970Scy.Pp 1678275970ScyDefault restriction list entries with the flags ignore, interface, 1679275970Scyntpport, for each of the local host's interface addresses are 1680275970Scyinserted into the table at startup to prevent the server 1681275970Scyfrom attempting to synchronize to its own time. 1682275970ScyA default entry is also always present, though if it is 1683275970Scyotherwise unconfigured; no flags are associated 1684275970Scywith the default entry (i.e., everything besides your own 1685275970ScyNTP server is unrestricted). 1686275970Scy.El 1687275970Scy.Sh Automatic NTP Configuration Options 1688275970Scy.Ss Manycasting 1689275970ScyManycasting is a automatic discovery and configuration paradigm 1690275970Scynew to NTPv4. 1691275970ScyIt is intended as a means for a multicast client 1692275970Scyto troll the nearby network neighborhood to find cooperating 1693275970Scymanycast servers, validate them using cryptographic means 1694275970Scyand evaluate their time values with respect to other servers 1695275970Scythat might be lurking in the vicinity. 1696275970ScyThe intended result is that each manycast client mobilizes 1697275970Scyclient associations with some number of the "best" 1698275970Scyof the nearby manycast servers, yet automatically reconfigures 1699275970Scyto sustain this number of servers should one or another fail. 1700275970Scy.Pp 1701275970ScyNote that the manycasting paradigm does not coincide 1702275970Scywith the anycast paradigm described in RFC\-1546, 1703275970Scywhich is designed to find a single server from a clique 1704275970Scyof servers providing the same service. 1705275970ScyThe manycast paradigm is designed to find a plurality 1706275970Scyof redundant servers satisfying defined optimality criteria. 1707275970Scy.Pp 1708275970ScyManycasting can be used with either symmetric key 1709275970Scyor public key cryptography. 1710275970ScyThe public key infrastructure (PKI) 1711275970Scyoffers the best protection against compromised keys 1712275970Scyand is generally considered stronger, at least with relatively 1713275970Scylarge key sizes. 1714275970ScyIt is implemented using the Autokey protocol and 1715275970Scythe OpenSSL cryptographic library available from 1716275970Scy.Li http://www.openssl.org/ . 1717275970ScyThe library can also be used with other NTPv4 modes 1718275970Scyas well and is highly recommended, especially for broadcast modes. 1719275970Scy.Pp 1720275970ScyA persistent manycast client association is configured 1721298770Sdelphijusing the 1722298770Sdelphij.Ic manycastclient 1723298770Sdelphijcommand, which is similar to the 1724298770Sdelphij.Ic server 1725298770Sdelphijcommand but with a multicast (IPv4 class 1726275970Scy.Cm D 1727275970Scyor IPv6 prefix 1728275970Scy.Cm FF ) 1729275970Scygroup address. 1730275970ScyThe IANA has designated IPv4 address 224.1.1.1 1731275970Scyand IPv6 address FF05::101 (site local) for NTP. 1732275970ScyWhen more servers are needed, it broadcasts manycast 1733275970Scyclient messages to this address at the minimum feasible rate 1734275970Scyand minimum feasible time\-to\-live (TTL) hops, depending 1735275970Scyon how many servers have already been found. 1736275970ScyThere can be as many manycast client associations 1737275970Scyas different group address, each one serving as a template 1738275970Scyfor a future ephemeral unicast client/server association. 1739275970Scy.Pp 1740275970ScyManycast servers configured with the 1741275970Scy.Ic manycastserver 1742275970Scycommand listen on the specified group address for manycast 1743275970Scyclient messages. 1744275970ScyNote the distinction between manycast client, 1745275970Scywhich actively broadcasts messages, and manycast server, 1746275970Scywhich passively responds to them. 1747275970ScyIf a manycast server is 1748275970Scyin scope of the current TTL and is itself synchronized 1749275970Scyto a valid source and operating at a stratum level equal 1750275970Scyto or lower than the manycast client, it replies to the 1751275970Scymanycast client message with an ordinary unicast server message. 1752275970Scy.Pp 1753275970ScyThe manycast client receiving this message mobilizes 1754275970Scyan ephemeral client/server association according to the 1755275970Scymatching manycast client template, but only if cryptographically 1756275970Scyauthenticated and the server stratum is less than or equal 1757275970Scyto the client stratum. 1758275970ScyAuthentication is explicitly required 1759275970Scyand either symmetric key or public key (Autokey) can be used. 1760275970ScyThen, the client polls the server at its unicast address 1761275970Scyin burst mode in order to reliably set the host clock 1762275970Scyand validate the source. 1763275970ScyThis normally results 1764275970Scyin a volley of eight client/server at 2\-s intervals 1765275970Scyduring which both the synchronization and cryptographic 1766275970Scyprotocols run concurrently. 1767275970ScyFollowing the volley, 1768275970Scythe client runs the NTP intersection and clustering 1769275970Scyalgorithms, which act to discard all but the "best" 1770275970Scyassociations according to stratum and synchronization 1771275970Scydistance. 1772275970ScyThe surviving associations then continue 1773275970Scyin ordinary client/server mode. 1774275970Scy.Pp 1775275970ScyThe manycast client polling strategy is designed to reduce 1776275970Scyas much as possible the volume of manycast client messages 1777275970Scyand the effects of implosion due to near\-simultaneous 1778275970Scyarrival of manycast server messages. 1779275970ScyThe strategy is determined by the 1780275970Scy.Ic manycastclient , 1781275970Scy.Ic tos 1782275970Scyand 1783275970Scy.Ic ttl 1784275970Scyconfiguration commands. 1785275970ScyThe manycast poll interval is 1786275970Scynormally eight times the system poll interval, 1787275970Scywhich starts out at the 1788275970Scy.Cm minpoll 1789275970Scyvalue specified in the 1790275970Scy.Ic manycastclient , 1791275970Scycommand and, under normal circumstances, increments to the 1792275970Scy.Cm maxpolll 1793275970Scyvalue specified in this command. 1794275970ScyInitially, the TTL is 1795298770Sdelphijset at the minimum hops specified by the 1796298770Sdelphij.Ic ttl 1797298770Sdelphijcommand. 1798275970ScyAt each retransmission the TTL is increased until reaching 1799275970Scythe maximum hops specified by this command or a sufficient 1800275970Scynumber client associations have been found. 1801275970ScyFurther retransmissions use the same TTL. 1802275970Scy.Pp 1803275970ScyThe quality and reliability of the suite of associations 1804275970Scydiscovered by the manycast client is determined by the NTP 1805275970Scymitigation algorithms and the 1806275970Scy.Cm minclock 1807275970Scyand 1808275970Scy.Cm minsane 1809275970Scyvalues specified in the 1810275970Scy.Ic tos 1811275970Scyconfiguration command. 1812275970ScyAt least 1813275970Scy.Cm minsane 1814275970Scycandidate servers must be available and the mitigation 1815275970Scyalgorithms produce at least 1816275970Scy.Cm minclock 1817275970Scysurvivors in order to synchronize the clock. 1818275970ScyByzantine agreement principles require at least four 1819275970Scycandidates in order to correctly discard a single falseticker. 1820275970ScyFor legacy purposes, 1821275970Scy.Cm minsane 1822275970Scydefaults to 1 and 1823275970Scy.Cm minclock 1824275970Scydefaults to 3. 1825275970ScyFor manycast service 1826275970Scy.Cm minsane 1827275970Scyshould be explicitly set to 4, assuming at least that 1828275970Scynumber of servers are available. 1829275970Scy.Pp 1830275970ScyIf at least 1831275970Scy.Cm minclock 1832275970Scyservers are found, the manycast poll interval is immediately 1833275970Scyset to eight times 1834275970Scy.Cm maxpoll . 1835275970ScyIf less than 1836275970Scy.Cm minclock 1837275970Scyservers are found when the TTL has reached the maximum hops, 1838275970Scythe manycast poll interval is doubled. 1839275970ScyFor each transmission 1840275970Scyafter that, the poll interval is doubled again until 1841275970Scyreaching the maximum of eight times 1842275970Scy.Cm maxpoll . 1843275970ScyFurther transmissions use the same poll interval and 1844275970ScyTTL values. 1845275970ScyNote that while all this is going on, 1846275970Scyeach client/server association found is operating normally 1847275970Scyit the system poll interval. 1848275970Scy.Pp 1849275970ScyAdministratively scoped multicast boundaries are normally 1850275970Scyspecified by the network router configuration and, 1851275970Scyin the case of IPv6, the link/site scope prefix. 1852275970ScyBy default, the increment for TTL hops is 32 starting 1853275970Scyfrom 31; however, the 1854275970Scy.Ic ttl 1855275970Scyconfiguration command can be 1856275970Scyused to modify the values to match the scope rules. 1857275970Scy.Pp 1858275970ScyIt is often useful to narrow the range of acceptable 1859275970Scyservers which can be found by manycast client associations. 1860275970ScyBecause manycast servers respond only when the client 1861275970Scystratum is equal to or greater than the server stratum, 1862275970Scyprimary (stratum 1) servers fill find only primary servers 1863275970Scyin TTL range, which is probably the most common objective. 1864275970ScyHowever, unless configured otherwise, all manycast clients 1865275970Scyin TTL range will eventually find all primary servers 1866275970Scyin TTL range, which is probably not the most common 1867275970Scyobjective in large networks. 1868275970ScyThe 1869275970Scy.Ic tos 1870275970Scycommand can be used to modify this behavior. 1871275970ScyServers with stratum below 1872275970Scy.Cm floor 1873275970Scyor above 1874275970Scy.Cm ceiling 1875275970Scyspecified in the 1876275970Scy.Ic tos 1877275970Scycommand are strongly discouraged during the selection 1878275970Scyprocess; however, these servers may be temporally 1879275970Scyaccepted if the number of servers within TTL range is 1880275970Scyless than 1881275970Scy.Cm minclock . 1882275970Scy.Pp 1883275970ScyThe above actions occur for each manycast client message, 1884275970Scywhich repeats at the designated poll interval. 1885275970ScyHowever, once the ephemeral client association is mobilized, 1886275970Scysubsequent manycast server replies are discarded, 1887275970Scysince that would result in a duplicate association. 1888275970ScyIf during a poll interval the number of client associations 1889275970Scyfalls below 1890275970Scy.Cm minclock , 1891275970Scyall manycast client prototype associations are reset 1892275970Scyto the initial poll interval and TTL hops and operation 1893275970Scyresumes from the beginning. 1894275970ScyIt is important to avoid 1895275970Scyfrequent manycast client messages, since each one requires 1896275970Scyall manycast servers in TTL range to respond. 1897275970ScyThe result could well be an implosion, either minor or major, 1898275970Scydepending on the number of servers in range. 1899275970ScyThe recommended value for 1900275970Scy.Cm maxpoll 1901275970Scyis 12 (4,096 s). 1902275970Scy.Pp 1903275970ScyIt is possible and frequently useful to configure a host 1904275970Scyas both manycast client and manycast server. 1905275970ScyA number of hosts configured this way and sharing a common 1906275970Scygroup address will automatically organize themselves 1907275970Scyin an optimum configuration based on stratum and 1908275970Scysynchronization distance. 1909275970ScyFor example, consider an NTP 1910275970Scysubnet of two primary servers and a hundred or more 1911275970Scydependent clients. 1912275970ScyWith two exceptions, all servers 1913275970Scyand clients have identical configuration files including both 1914275970Scy.Ic multicastclient 1915275970Scyand 1916275970Scy.Ic multicastserver 1917275970Scycommands using, for instance, multicast group address 1918275970Scy239.1.1.1. 1919275970ScyThe only exception is that each primary server 1920275970Scyconfiguration file must include commands for the primary 1921275970Scyreference source such as a GPS receiver. 1922275970Scy.Pp 1923275970ScyThe remaining configuration files for all secondary 1924275970Scyservers and clients have the same contents, except for the 1925275970Scy.Ic tos 1926275970Scycommand, which is specific for each stratum level. 1927275970ScyFor stratum 1 and stratum 2 servers, that command is 1928275970Scynot necessary. 1929275970ScyFor stratum 3 and above servers the 1930275970Scy.Cm floor 1931275970Scyvalue is set to the intended stratum number. 1932275970ScyThus, all stratum 3 configuration files are identical, 1933275970Scyall stratum 4 files are identical and so forth. 1934275970Scy.Pp 1935275970ScyOnce operations have stabilized in this scenario, 1936275970Scythe primary servers will find the primary reference source 1937275970Scyand each other, since they both operate at the same 1938275970Scystratum (1), but not with any secondary server or client, 1939275970Scysince these operate at a higher stratum. 1940275970ScyThe secondary 1941275970Scyservers will find the servers at the same stratum level. 1942275970ScyIf one of the primary servers loses its GPS receiver, 1943275970Scyit will continue to operate as a client and other clients 1944275970Scywill time out the corresponding association and 1945275970Scyre\-associate accordingly. 1946275970Scy.Pp 1947275970ScySome administrators prefer to avoid running 1948275970Scy.Xr ntpd 1ntpdmdoc 1949275970Scycontinuously and run either 1950289999Sglebius.Xr sntp 1sntpmdoc 1951275970Scyor 1952275970Scy.Xr ntpd 1ntpdmdoc 1953275970Scy.Fl q 1954275970Scyas a cron job. 1955275970ScyIn either case the servers must be 1956275970Scyconfigured in advance and the program fails if none are 1957275970Scyavailable when the cron job runs. 1958275970ScyA really slick 1959275970Scyapplication of manycast is with 1960275970Scy.Xr ntpd 1ntpdmdoc 1961275970Scy.Fl q . 1962275970ScyThe program wakes up, scans the local landscape looking 1963275970Scyfor the usual suspects, selects the best from among 1964275970Scythe rascals, sets the clock and then departs. 1965275970ScyServers do not have to be configured in advance and 1966275970Scyall clients throughout the network can have the same 1967275970Scyconfiguration file. 1968275970Scy.Ss Manycast Interactions with Autokey 1969275970ScyEach time a manycast client sends a client mode packet 1970275970Scyto a multicast group address, all manycast servers 1971275970Scyin scope generate a reply including the host name 1972275970Scyand status word. 1973275970ScyThe manycast clients then run 1974275970Scythe Autokey protocol, which collects and verifies 1975275970Scyall certificates involved. 1976275970ScyFollowing the burst interval 1977275970Scyall but three survivors are cast off, 1978275970Scybut the certificates remain in the local cache. 1979275970ScyIt often happens that several complete signing trails 1980275970Scyfrom the client to the primary servers are collected in this way. 1981275970Scy.Pp 1982275970ScyAbout once an hour or less often if the poll interval 1983275970Scyexceeds this, the client regenerates the Autokey key list. 1984275970ScyThis is in general transparent in client/server mode. 1985275970ScyHowever, about once per day the server private value 1986275970Scyused to generate cookies is refreshed along with all 1987275970Scymanycast client associations. 1988275970ScyIn this case all 1989275970Scycryptographic values including certificates is refreshed. 1990275970ScyIf a new certificate has been generated since 1991275970Scythe last refresh epoch, it will automatically revoke 1992275970Scyall prior certificates that happen to be in the 1993275970Scycertificate cache. 1994275970ScyAt the same time, the manycast 1995275970Scyscheme starts all over from the beginning and 1996275970Scythe expanding ring shrinks to the minimum and increments 1997275970Scyfrom there while collecting all servers in scope. 1998275970Scy.Ss Manycast Options 1999275970Scy.Bl -tag -width indent 2000275970Scy.It Xo Ic tos 2001275970Scy.Oo 2002275970Scy.Cm ceiling Ar ceiling | 2003275970Scy.Cm cohort { 0 | 1 } | 2004275970Scy.Cm floor Ar floor | 2005275970Scy.Cm minclock Ar minclock | 2006275970Scy.Cm minsane Ar minsane 2007275970Scy.Oc 2008275970Scy.Xc 2009275970ScyThis command affects the clock selection and clustering 2010275970Scyalgorithms. 2011275970ScyIt can be used to select the quality and 2012275970Scyquantity of peers used to synchronize the system clock 2013275970Scyand is most useful in manycast mode. 2014275970ScyThe variables operate 2015275970Scyas follows: 2016275970Scy.Bl -tag -width indent 2017275970Scy.It Cm ceiling Ar ceiling 2018275970ScyPeers with strata above 2019275970Scy.Cm ceiling 2020275970Scywill be discarded if there are at least 2021275970Scy.Cm minclock 2022275970Scypeers remaining. 2023275970ScyThis value defaults to 15, but can be changed 2024275970Scyto any number from 1 to 15. 2025275970Scy.It Cm cohort Bro 0 | 1 Brc 2026275970ScyThis is a binary flag which enables (0) or disables (1) 2027275970Scymanycast server replies to manycast clients with the same 2028275970Scystratum level. 2029275970ScyThis is useful to reduce implosions where 2030275970Scylarge numbers of clients with the same stratum level 2031275970Scyare present. 2032275970ScyThe default is to enable these replies. 2033275970Scy.It Cm floor Ar floor 2034275970ScyPeers with strata below 2035275970Scy.Cm floor 2036275970Scywill be discarded if there are at least 2037275970Scy.Cm minclock 2038275970Scypeers remaining. 2039275970ScyThis value defaults to 1, but can be changed 2040275970Scyto any number from 1 to 15. 2041275970Scy.It Cm minclock Ar minclock 2042289999SglebiusThe clustering algorithm repeatedly casts out outlier 2043275970Scyassociations until no more than 2044275970Scy.Cm minclock 2045275970Scyassociations remain. 2046275970ScyThis value defaults to 3, 2047275970Scybut can be changed to any number from 1 to the number of 2048275970Scyconfigured sources. 2049275970Scy.It Cm minsane Ar minsane 2050275970ScyThis is the minimum number of candidates available 2051275970Scyto the clock selection algorithm in order to produce 2052275970Scyone or more truechimers for the clustering algorithm. 2053275970ScyIf fewer than this number are available, the clock is 2054275970Scyundisciplined and allowed to run free. 2055275970ScyThe default is 1 2056275970Scyfor legacy purposes. 2057275970ScyHowever, according to principles of 2058275970ScyByzantine agreement, 2059275970Scy.Cm minsane 2060275970Scyshould be at least 4 in order to detect and discard 2061275970Scya single falseticker. 2062275970Scy.El 2063275970Scy.It Cm ttl Ar hop ... 2064275970ScyThis command specifies a list of TTL values in increasing 2065275970Scyorder, up to 8 values can be specified. 2066275970ScyIn manycast mode these values are used in turn 2067275970Scyin an expanding\-ring search. 2068275970ScyThe default is eight 2069275970Scymultiples of 32 starting at 31. 2070275970Scy.El 2071275970Scy.Sh Reference Clock Support 2072275970ScyThe NTP Version 4 daemon supports some three dozen different radio, 2073275970Scysatellite and modem reference clocks plus a special pseudo\-clock 2074275970Scyused for backup or when no other clock source is available. 2075275970ScyDetailed descriptions of individual device drivers and options can 2076275970Scybe found in the 2077275970Scy.Qq Reference Clock Drivers 2078275970Scypage 2079275970Scy(available as part of the HTML documentation 2080275970Scyprovided in 2081275970Scy.Pa /usr/share/doc/ntp ) . 2082275970ScyAdditional information can be found in the pages linked 2083275970Scythere, including the 2084275970Scy.Qq Debugging Hints for Reference Clock Drivers 2085275970Scyand 2086275970Scy.Qq How To Write a Reference Clock Driver 2087275970Scypages 2088275970Scy(available as part of the HTML documentation 2089275970Scyprovided in 2090275970Scy.Pa /usr/share/doc/ntp ) . 2091275970ScyIn addition, support for a PPS 2092275970Scysignal is available as described in the 2093275970Scy.Qq Pulse\-per\-second (PPS) Signal Interfacing 2094275970Scypage 2095275970Scy(available as part of the HTML documentation 2096275970Scyprovided in 2097275970Scy.Pa /usr/share/doc/ntp ) . 2098275970ScyMany 2099275970Scydrivers support special line discipline/streams modules which can 2100275970Scysignificantly improve the accuracy using the driver. 2101275970ScyThese are 2102275970Scydescribed in the 2103275970Scy.Qq Line Disciplines and Streams Drivers 2104275970Scypage 2105275970Scy(available as part of the HTML documentation 2106275970Scyprovided in 2107275970Scy.Pa /usr/share/doc/ntp ) . 2108275970Scy.Pp 2109275970ScyA reference clock will generally (though not always) be a radio 2110275970Scytimecode receiver which is synchronized to a source of standard 2111275970Scytime such as the services offered by the NRC in Canada and NIST and 2112275970ScyUSNO in the US. 2113275970ScyThe interface between the computer and the timecode 2114275970Scyreceiver is device dependent, but is usually a serial port. 2115275970ScyA 2116275970Scydevice driver specific to each reference clock must be selected and 2117275970Scycompiled in the distribution; however, most common radio, satellite 2118275970Scyand modem clocks are included by default. 2119275970ScyNote that an attempt to 2120275970Scyconfigure a reference clock when the driver has not been compiled 2121275970Scyor the hardware port has not been appropriately configured results 2122275970Scyin a scalding remark to the system log file, but is otherwise non 2123275970Scyhazardous. 2124275970Scy.Pp 2125275970ScyFor the purposes of configuration, 2126275970Scy.Xr ntpd 1ntpdmdoc 2127275970Scytreats 2128275970Scyreference clocks in a manner analogous to normal NTP peers as much 2129275970Scyas possible. 2130275970ScyReference clocks are identified by a syntactically 2131275970Scycorrect but invalid IP address, in order to distinguish them from 2132275970Scynormal NTP peers. 2133275970ScyReference clock addresses are of the form 2134275970Scy.Sm off 2135275970Scy.Li 127.127. Ar t . Ar u , 2136275970Scy.Sm on 2137275970Scywhere 2138275970Scy.Ar t 2139275970Scyis an integer 2140275970Scydenoting the clock type and 2141275970Scy.Ar u 2142275970Scyindicates the unit 2143275970Scynumber in the range 0\-3. 2144275970ScyWhile it may seem overkill, it is in fact 2145275970Scysometimes useful to configure multiple reference clocks of the same 2146275970Scytype, in which case the unit numbers must be unique. 2147275970Scy.Pp 2148275970ScyThe 2149275970Scy.Ic server 2150275970Scycommand is used to configure a reference 2151275970Scyclock, where the 2152275970Scy.Ar address 2153275970Scyargument in that command 2154275970Scyis the clock address. 2155275970ScyThe 2156275970Scy.Cm key , 2157275970Scy.Cm version 2158275970Scyand 2159275970Scy.Cm ttl 2160275970Scyoptions are not used for reference clock support. 2161275970ScyThe 2162275970Scy.Cm mode 2163275970Scyoption is added for reference clock support, as 2164275970Scydescribed below. 2165275970ScyThe 2166275970Scy.Cm prefer 2167275970Scyoption can be useful to 2168275970Scypersuade the server to cherish a reference clock with somewhat more 2169275970Scyenthusiasm than other reference clocks or peers. 2170275970ScyFurther 2171275970Scyinformation on this option can be found in the 2172275970Scy.Qq Mitigation Rules and the prefer Keyword 2173275970Scy(available as part of the HTML documentation 2174275970Scyprovided in 2175275970Scy.Pa /usr/share/doc/ntp ) 2176275970Scypage. 2177275970ScyThe 2178275970Scy.Cm minpoll 2179275970Scyand 2180275970Scy.Cm maxpoll 2181275970Scyoptions have 2182275970Scymeaning only for selected clock drivers. 2183275970ScySee the individual clock 2184275970Scydriver document pages for additional information. 2185275970Scy.Pp 2186275970ScyThe 2187275970Scy.Ic fudge 2188275970Scycommand is used to provide additional 2189275970Scyinformation for individual clock drivers and normally follows 2190275970Scyimmediately after the 2191275970Scy.Ic server 2192275970Scycommand. 2193275970ScyThe 2194275970Scy.Ar address 2195275970Scyargument specifies the clock address. 2196275970ScyThe 2197275970Scy.Cm refid 2198275970Scyand 2199275970Scy.Cm stratum 2200275970Scyoptions can be used to 2201275970Scyoverride the defaults for the device. 2202275970ScyThere are two optional 2203275970Scydevice\-dependent time offsets and four flags that can be included 2204275970Scyin the 2205275970Scy.Ic fudge 2206275970Scycommand as well. 2207275970Scy.Pp 2208275970ScyThe stratum number of a reference clock is by default zero. 2209275970ScySince the 2210275970Scy.Xr ntpd 1ntpdmdoc 2211275970Scydaemon adds one to the stratum of each 2212275970Scypeer, a primary server ordinarily displays an external stratum of 2213275970Scyone. 2214275970ScyIn order to provide engineered backups, it is often useful to 2215275970Scyspecify the reference clock stratum as greater than zero. 2216275970ScyThe 2217275970Scy.Cm stratum 2218275970Scyoption is used for this purpose. 2219275970ScyAlso, in cases 2220275970Scyinvolving both a reference clock and a pulse\-per\-second (PPS) 2221275970Scydiscipline signal, it is useful to specify the reference clock 2222275970Scyidentifier as other than the default, depending on the driver. 2223275970ScyThe 2224275970Scy.Cm refid 2225275970Scyoption is used for this purpose. 2226275970ScyExcept where noted, 2227275970Scythese options apply to all clock drivers. 2228275970Scy.Ss Reference Clock Commands 2229275970Scy.Bl -tag -width indent 2230275970Scy.It Xo Ic server 2231275970Scy.Sm off 2232275970Scy.Li 127.127. Ar t . Ar u 2233275970Scy.Sm on 2234275970Scy.Op Cm prefer 2235275970Scy.Op Cm mode Ar int 2236275970Scy.Op Cm minpoll Ar int 2237275970Scy.Op Cm maxpoll Ar int 2238275970Scy.Xc 2239275970ScyThis command can be used to configure reference clocks in 2240275970Scyspecial ways. 2241275970ScyThe options are interpreted as follows: 2242275970Scy.Bl -tag -width indent 2243275970Scy.It Cm prefer 2244275970ScyMarks the reference clock as preferred. 2245275970ScyAll other things being 2246275970Scyequal, this host will be chosen for synchronization among a set of 2247275970Scycorrectly operating hosts. 2248275970ScySee the 2249275970Scy.Qq Mitigation Rules and the prefer Keyword 2250275970Scypage 2251275970Scy(available as part of the HTML documentation 2252275970Scyprovided in 2253275970Scy.Pa /usr/share/doc/ntp ) 2254275970Scyfor further information. 2255275970Scy.It Cm mode Ar int 2256275970ScySpecifies a mode number which is interpreted in a 2257275970Scydevice\-specific fashion. 2258275970ScyFor instance, it selects a dialing 2259275970Scyprotocol in the ACTS driver and a device subtype in the 2260275970Scyparse 2261275970Scydrivers. 2262275970Scy.It Cm minpoll Ar int 2263275970Scy.It Cm maxpoll Ar int 2264275970ScyThese options specify the minimum and maximum polling interval 2265275970Scyfor reference clock messages, as a power of 2 in seconds 2266275970ScyFor 2267275970Scymost directly connected reference clocks, both 2268275970Scy.Cm minpoll 2269275970Scyand 2270275970Scy.Cm maxpoll 2271275970Scydefault to 6 (64 s). 2272275970ScyFor modem reference clocks, 2273275970Scy.Cm minpoll 2274275970Scydefaults to 10 (17.1 m) and 2275275970Scy.Cm maxpoll 2276275970Scydefaults to 14 (4.5 h). 2277275970ScyThe allowable range is 4 (16 s) to 17 (36.4 h) inclusive. 2278275970Scy.El 2279275970Scy.It Xo Ic fudge 2280275970Scy.Sm off 2281275970Scy.Li 127.127. Ar t . Ar u 2282275970Scy.Sm on 2283275970Scy.Op Cm time1 Ar sec 2284275970Scy.Op Cm time2 Ar sec 2285275970Scy.Op Cm stratum Ar int 2286275970Scy.Op Cm refid Ar string 2287275970Scy.Op Cm mode Ar int 2288275970Scy.Op Cm flag1 Cm 0 \&| Cm 1 2289275970Scy.Op Cm flag2 Cm 0 \&| Cm 1 2290275970Scy.Op Cm flag3 Cm 0 \&| Cm 1 2291275970Scy.Op Cm flag4 Cm 0 \&| Cm 1 2292275970Scy.Xc 2293275970ScyThis command can be used to configure reference clocks in 2294275970Scyspecial ways. 2295275970ScyIt must immediately follow the 2296275970Scy.Ic server 2297275970Scycommand which configures the driver. 2298275970ScyNote that the same capability 2299275970Scyis possible at run time using the 2300275970Scy.Xr ntpdc 1ntpdcmdoc 2301275970Scyprogram. 2302275970ScyThe options are interpreted as 2303275970Scyfollows: 2304275970Scy.Bl -tag -width indent 2305275970Scy.It Cm time1 Ar sec 2306275970ScySpecifies a constant to be added to the time offset produced by 2307275970Scythe driver, a fixed\-point decimal number in seconds. 2308275970ScyThis is used 2309275970Scyas a calibration constant to adjust the nominal time offset of a 2310275970Scyparticular clock to agree with an external standard, such as a 2311275970Scyprecision PPS signal. 2312275970ScyIt also provides a way to correct a 2313275970Scysystematic error or bias due to serial port or operating system 2314275970Scylatencies, different cable lengths or receiver internal delay. 2315275970ScyThe 2316275970Scyspecified offset is in addition to the propagation delay provided 2317275970Scyby other means, such as internal DIPswitches. 2318275970ScyWhere a calibration 2319275970Scyfor an individual system and driver is available, an approximate 2320275970Scycorrection is noted in the driver documentation pages. 2321275970ScyNote: in order to facilitate calibration when more than one 2322275970Scyradio clock or PPS signal is supported, a special calibration 2323275970Scyfeature is available. 2324275970ScyIt takes the form of an argument to the 2325275970Scy.Ic enable 2326275970Scycommand described in 2327275970Scy.Sx Miscellaneous Options 2328275970Scypage and operates as described in the 2329275970Scy.Qq Reference Clock Drivers 2330275970Scypage 2331275970Scy(available as part of the HTML documentation 2332275970Scyprovided in 2333275970Scy.Pa /usr/share/doc/ntp ) . 2334275970Scy.It Cm time2 Ar secs 2335275970ScySpecifies a fixed\-point decimal number in seconds, which is 2336275970Scyinterpreted in a driver\-dependent way. 2337275970ScySee the descriptions of 2338275970Scyspecific drivers in the 2339275970Scy.Qq Reference Clock Drivers 2340275970Scypage 2341275970Scy(available as part of the HTML documentation 2342275970Scyprovided in 2343275970Scy.Pa /usr/share/doc/ntp ) . 2344275970Scy.It Cm stratum Ar int 2345275970ScySpecifies the stratum number assigned to the driver, an integer 2346275970Scybetween 0 and 15. 2347275970ScyThis number overrides the default stratum number 2348275970Scyordinarily assigned by the driver itself, usually zero. 2349275970Scy.It Cm refid Ar string 2350275970ScySpecifies an ASCII string of from one to four characters which 2351275970Scydefines the reference identifier used by the driver. 2352275970ScyThis string 2353275970Scyoverrides the default identifier ordinarily assigned by the driver 2354275970Scyitself. 2355275970Scy.It Cm mode Ar int 2356275970ScySpecifies a mode number which is interpreted in a 2357275970Scydevice\-specific fashion. 2358275970ScyFor instance, it selects a dialing 2359275970Scyprotocol in the ACTS driver and a device subtype in the 2360275970Scyparse 2361275970Scydrivers. 2362275970Scy.It Cm flag1 Cm 0 \&| Cm 1 2363275970Scy.It Cm flag2 Cm 0 \&| Cm 1 2364275970Scy.It Cm flag3 Cm 0 \&| Cm 1 2365275970Scy.It Cm flag4 Cm 0 \&| Cm 1 2366275970ScyThese four flags are used for customizing the clock driver. 2367275970ScyThe 2368275970Scyinterpretation of these values, and whether they are used at all, 2369275970Scyis a function of the particular clock driver. 2370275970ScyHowever, by 2371275970Scyconvention 2372275970Scy.Cm flag4 2373275970Scyis used to enable recording monitoring 2374275970Scydata to the 2375275970Scy.Cm clockstats 2376275970Scyfile configured with the 2377275970Scy.Ic filegen 2378275970Scycommand. 2379275970ScyFurther information on the 2380275970Scy.Ic filegen 2381275970Scycommand can be found in 2382275970Scy.Sx Monitoring Options . 2383275970Scy.El 2384275970Scy.El 2385275970Scy.Sh Miscellaneous Options 2386275970Scy.Bl -tag -width indent 2387275970Scy.It Ic broadcastdelay Ar seconds 2388275970ScyThe broadcast and multicast modes require a special calibration 2389275970Scyto determine the network delay between the local and remote 2390275970Scyservers. 2391275970ScyOrdinarily, this is done automatically by the initial 2392275970Scyprotocol exchanges between the client and server. 2393275970ScyIn some cases, 2394275970Scythe calibration procedure may fail due to network or server access 2395275970Scycontrols, for example. 2396275970ScyThis command specifies the default delay to 2397275970Scybe used under these circumstances. 2398275970ScyTypically (for Ethernet), a 2399275970Scynumber between 0.003 and 0.007 seconds is appropriate. 2400275970ScyThe default 2401275970Scywhen this command is not used is 0.004 seconds. 2402275970Scy.It Ic calldelay Ar delay 2403275970ScyThis option controls the delay in seconds between the first and second 2404275970Scypackets sent in burst or iburst mode to allow additional time for a modem 2405275970Scyor ISDN call to complete. 2406275970Scy.It Ic driftfile Ar driftfile 2407275970ScyThis command specifies the complete path and name of the file used to 2408275970Scyrecord the frequency of the local clock oscillator. 2409275970ScyThis is the same 2410275970Scyoperation as the 2411275970Scy.Fl f 2412275970Scycommand line option. 2413275970ScyIf the file exists, it is read at 2414275970Scystartup in order to set the initial frequency and then updated once per 2415275970Scyhour with the current frequency computed by the daemon. 2416275970ScyIf the file name is 2417275970Scyspecified, but the file itself does not exist, the starts with an initial 2418275970Scyfrequency of zero and creates the file when writing it for the first time. 2419275970ScyIf this command is not given, the daemon will always start with an initial 2420275970Scyfrequency of zero. 2421275970Scy.Pp 2422275970ScyThe file format consists of a single line containing a single 2423275970Scyfloating point number, which records the frequency offset measured 2424275970Scyin parts\-per\-million (PPM). 2425275970ScyThe file is updated by first writing 2426275970Scythe current drift value into a temporary file and then renaming 2427275970Scythis file to replace the old version. 2428275970ScyThis implies that 2429275970Scy.Xr ntpd 1ntpdmdoc 2430275970Scymust have write permission for the directory the 2431275970Scydrift file is located in, and that file system links, symbolic or 2432275970Scyotherwise, should be avoided. 2433285612Sdelphij.It Ic dscp Ar value 2434285612SdelphijThis option specifies the Differentiated Services Control Point (DSCP) value, 2435298770Sdelphija 6\-bit code. 2436298770SdelphijThe default value is 46, signifying Expedited Forwarding. 2437275970Scy.It Xo Ic enable 2438275970Scy.Oo 2439275970Scy.Cm auth | Cm bclient | 2440275970Scy.Cm calibrate | Cm kernel | 2441294904Sdelphij.Cm mode7 | Cm monitor | 2442294904Sdelphij.Cm ntp | Cm stats | 2443294904Sdelphij.Cm unpeer_crypto_early | Cm unpeer_crypto_nak_early | Cm unpeer_digest_early 2444275970Scy.Oc 2445275970Scy.Xc 2446275970Scy.It Xo Ic disable 2447275970Scy.Oo 2448275970Scy.Cm auth | Cm bclient | 2449275970Scy.Cm calibrate | Cm kernel | 2450294904Sdelphij.Cm mode7 | Cm monitor | 2451294904Sdelphij.Cm ntp | Cm stats | 2452294904Sdelphij.Cm unpeer_crypto_early | Cm unpeer_crypto_nak_early | Cm unpeer_digest_early 2453275970Scy.Oc 2454275970Scy.Xc 2455275970ScyProvides a way to enable or disable various server options. 2456275970ScyFlags not mentioned are unaffected. 2457275970ScyNote that all of these flags 2458275970Scycan be controlled remotely using the 2459275970Scy.Xr ntpdc 1ntpdcmdoc 2460275970Scyutility program. 2461275970Scy.Bl -tag -width indent 2462275970Scy.It Cm auth 2463275970ScyEnables the server to synchronize with unconfigured peers only if the 2464275970Scypeer has been correctly authenticated using either public key or 2465275970Scyprivate key cryptography. 2466275970ScyThe default for this flag is 2467275970Scy.Ic enable . 2468275970Scy.It Cm bclient 2469275970ScyEnables the server to listen for a message from a broadcast or 2470275970Scymulticast server, as in the 2471275970Scy.Ic multicastclient 2472275970Scycommand with default 2473275970Scyaddress. 2474275970ScyThe default for this flag is 2475275970Scy.Ic disable . 2476275970Scy.It Cm calibrate 2477275970ScyEnables the calibrate feature for reference clocks. 2478275970ScyThe default for 2479275970Scythis flag is 2480275970Scy.Ic disable . 2481275970Scy.It Cm kernel 2482275970ScyEnables the kernel time discipline, if available. 2483275970ScyThe default for this 2484275970Scyflag is 2485275970Scy.Ic enable 2486275970Scyif support is available, otherwise 2487275970Scy.Ic disable . 2488275970Scy.It Cm mode7 2489275970ScyEnables processing of NTP mode 7 implementation\-specific requests 2490275970Scywhich are used by the deprecated 2491275970Scy.Xr ntpdc 1ntpdcmdoc 2492275970Scyprogram. 2493275970ScyThe default for this flag is disable. 2494275970ScyThis flag is excluded from runtime configuration using 2495275970Scy.Xr ntpq 1ntpqmdoc . 2496275970ScyThe 2497275970Scy.Xr ntpq 1ntpqmdoc 2498275970Scyprogram provides the same capabilities as 2499275970Scy.Xr ntpdc 1ntpdcmdoc 2500275970Scyusing standard mode 6 requests. 2501275970Scy.It Cm monitor 2502275970ScyEnables the monitoring facility. 2503275970ScySee the 2504275970Scy.Xr ntpdc 1ntpdcmdoc 2505275970Scyprogram 2506275970Scyand the 2507275970Scy.Ic monlist 2508275970Scycommand or further information. 2509275970ScyThe 2510275970Scydefault for this flag is 2511275970Scy.Ic enable . 2512275970Scy.It Cm ntp 2513275970ScyEnables time and frequency discipline. 2514275970ScyIn effect, this switch opens and 2515275970Scycloses the feedback loop, which is useful for testing. 2516275970ScyThe default for 2517275970Scythis flag is 2518275970Scy.Ic enable . 2519275970Scy.It Cm stats 2520275970ScyEnables the statistics facility. 2521275970ScySee the 2522275970Scy.Sx Monitoring Options 2523275970Scysection for further information. 2524275970ScyThe default for this flag is 2525275970Scy.Ic disable . 2526294904Sdelphij.It Cm unpeer_crypto_early 2527294904SdelphijBy default, if 2528294904Sdelphij.Xr ntpd 1ntpdmdoc 2529294904Sdelphijreceives an autokey packet that fails TEST9, 2530294904Sdelphija crypto failure, 2531294904Sdelphijthe association is immediately cleared. 2532294904SdelphijThis is almost certainly a feature, 2533294904Sdelphijbut if, in spite of the current recommendation of not using autokey, 2534294904Sdelphijyou are 2535294904Sdelphij.B still 2536294904Sdelphijusing autokey 2537294904Sdelphij.B and 2538294904Sdelphijyou are seeing this sort of DoS attack 2539294904Sdelphijdisabling this flag will delay 2540294904Sdelphijtearing down the association until the reachability counter 2541294904Sdelphijbecomes zero. 2542294904SdelphijYou can check your 2543294904Sdelphij.Cm peerstats 2544294904Sdelphijfile for evidence of any of these attacks. 2545294904SdelphijThe 2546294904Sdelphijdefault for this flag is 2547294904Sdelphij.Ic enable . 2548294904Sdelphij.It Cm unpeer_crypto_nak_early 2549294904SdelphijBy default, if 2550294904Sdelphij.Xr ntpd 1ntpdmdoc 2551294904Sdelphijreceives a crypto\-NAK packet that 2552294904Sdelphijpasses the duplicate packet and origin timestamp checks 2553294904Sdelphijthe association is immediately cleared. 2554294904SdelphijWhile this is generally a feature 2555294904Sdelphijas it allows for quick recovery if a server key has changed, 2556294904Sdelphija properly forged and appropriately delivered crypto\-NAK packet 2557294904Sdelphijcan be used in a DoS attack. 2558294904SdelphijIf you have active noticable problems with this type of DoS attack 2559294904Sdelphijthen you should consider 2560294904Sdelphijdisabling this option. 2561294904SdelphijYou can check your 2562294904Sdelphij.Cm peerstats 2563294904Sdelphijfile for evidence of any of these attacks. 2564294904SdelphijThe 2565294904Sdelphijdefault for this flag is 2566294904Sdelphij.Ic enable . 2567294904Sdelphij.It Cm unpeer_digest_early 2568294904SdelphijBy default, if 2569294904Sdelphij.Xr ntpd 1ntpdmdoc 2570294904Sdelphijreceives what should be an authenticated packet 2571294904Sdelphijthat passes other packet sanity checks but 2572294904Sdelphijcontains an invalid digest 2573294904Sdelphijthe association is immediately cleared. 2574294904SdelphijWhile this is generally a feature 2575294904Sdelphijas it allows for quick recovery, 2576294904Sdelphijif this type of packet is carefully forged and sent 2577294904Sdelphijduring an appropriate window it can be used for a DoS attack. 2578294904SdelphijIf you have active noticable problems with this type of DoS attack 2579294904Sdelphijthen you should consider 2580294904Sdelphijdisabling this option. 2581294904SdelphijYou can check your 2582294904Sdelphij.Cm peerstats 2583294904Sdelphijfile for evidence of any of these attacks. 2584294904SdelphijThe 2585294904Sdelphijdefault for this flag is 2586294904Sdelphij.Ic enable . 2587275970Scy.El 2588275970Scy.It Ic includefile Ar includefile 2589275970ScyThis command allows additional configuration commands 2590275970Scyto be included from a separate file. 2591275970ScyInclude files may 2592275970Scybe nested to a depth of five; upon reaching the end of any 2593275970Scyinclude file, command processing resumes in the previous 2594275970Scyconfiguration file. 2595275970ScyThis option is useful for sites that run 2596275970Scy.Xr ntpd 1ntpdmdoc 2597275970Scyon multiple hosts, with (mostly) common options (e.g., a 2598275970Scyrestriction list). 2599285612Sdelphij.It Ic leapsmearinterval Ar seconds 2600285612SdelphijThis EXPERIMENTAL option is only available if 2601285612Sdelphij.Xr ntpd 1ntpdmdoc 2602285612Sdelphijwas built with the 2603285612Sdelphij.Cm \-\-enable\-leap\-smear 2604285612Sdelphijoption to the 2605285612Sdelphij.Cm configure 2606285612Sdelphijscript. 2607285612SdelphijIt specifies the interval over which a leap second correction will be applied. 2608285612SdelphijRecommended values for this option are between 2609285612Sdelphij7200 (2 hours) and 86400 (24 hours). 2610285612Sdelphij.Sy DO NOT USE THIS OPTION ON PUBLIC\-ACCESS SERVERS! 2611285612SdelphijSee http://bugs.ntp.org/2855 for more information. 2612275970Scy.It Ic logconfig Ar configkeyword 2613275970ScyThis command controls the amount and type of output written to 2614275970Scythe system 2615275970Scy.Xr syslog 3 2616275970Scyfacility or the alternate 2617275970Scy.Ic logfile 2618275970Scylog file. 2619275970ScyBy default, all output is turned on. 2620275970ScyAll 2621275970Scy.Ar configkeyword 2622275970Scykeywords can be prefixed with 2623275970Scy.Ql = , 2624275970Scy.Ql + 2625275970Scyand 2626275970Scy.Ql \- , 2627275970Scywhere 2628275970Scy.Ql = 2629275970Scysets the 2630275970Scy.Xr syslog 3 2631275970Scypriority mask, 2632275970Scy.Ql + 2633275970Scyadds and 2634275970Scy.Ql \- 2635275970Scyremoves 2636275970Scymessages. 2637275970Scy.Xr syslog 3 2638275970Scymessages can be controlled in four 2639275970Scyclasses 2640275970Scy.Po 2641275970Scy.Cm clock , 2642275970Scy.Cm peer , 2643275970Scy.Cm sys 2644275970Scyand 2645275970Scy.Cm sync 2646275970Scy.Pc . 2647275970ScyWithin these classes four types of messages can be 2648275970Scycontrolled: informational messages 2649275970Scy.Po 2650275970Scy.Cm info 2651275970Scy.Pc , 2652275970Scyevent messages 2653275970Scy.Po 2654275970Scy.Cm events 2655275970Scy.Pc , 2656275970Scystatistics messages 2657275970Scy.Po 2658275970Scy.Cm statistics 2659275970Scy.Pc 2660275970Scyand 2661275970Scystatus messages 2662275970Scy.Po 2663275970Scy.Cm status 2664275970Scy.Pc . 2665275970Scy.Pp 2666275970ScyConfiguration keywords are formed by concatenating the message class with 2667275970Scythe event class. 2668275970ScyThe 2669275970Scy.Cm all 2670275970Scyprefix can be used instead of a message class. 2671275970ScyA 2672275970Scymessage class may also be followed by the 2673275970Scy.Cm all 2674275970Scykeyword to enable/disable all 2675298770Sdelphijmessages of the respective message class. 2676298770SdelphijThus, a minimal log configuration 2677275970Scycould look like this: 2678275970Scy.Bd -literal 2679275970Scylogconfig =syncstatus +sysevents 2680275970Scy.Ed 2681275970Scy.Pp 2682275970ScyThis would just list the synchronizations state of 2683275970Scy.Xr ntpd 1ntpdmdoc 2684275970Scyand the major system events. 2685275970ScyFor a simple reference server, the 2686275970Scyfollowing minimum message configuration could be useful: 2687275970Scy.Bd -literal 2688275970Scylogconfig =syncall +clockall 2689275970Scy.Ed 2690275970Scy.Pp 2691275970ScyThis configuration will list all clock information and 2692275970Scysynchronization information. 2693275970ScyAll other events and messages about 2694275970Scypeers, system events and so on is suppressed. 2695275970Scy.It Ic logfile Ar logfile 2696275970ScyThis command specifies the location of an alternate log file to 2697275970Scybe used instead of the default system 2698275970Scy.Xr syslog 3 2699275970Scyfacility. 2700298770SdelphijThis is the same operation as the 2701298770Sdelphij.Fl l 2702298770Sdelphijcommand line option. 2703275970Scy.It Ic setvar Ar variable Op Cm default 2704275970ScyThis command adds an additional system variable. 2705275970ScyThese 2706275970Scyvariables can be used to distribute additional information such as 2707275970Scythe access policy. 2708275970ScyIf the variable of the form 2709275970Scy.Sm off 2710275970Scy.Va name = Ar value 2711275970Scy.Sm on 2712275970Scyis followed by the 2713275970Scy.Cm default 2714275970Scykeyword, the 2715275970Scyvariable will be listed as part of the default system variables 2716275970Scy.Po 2717275970Scy.Xr ntpq 1ntpqmdoc 2718275970Scy.Ic rv 2719275970Scycommand 2720275970Scy.Pc ) . 2721275970ScyThese additional variables serve 2722275970Scyinformational purposes only. 2723275970ScyThey are not related to the protocol 2724275970Scyother that they can be listed. 2725275970ScyThe known protocol variables will 2726275970Scyalways override any variables defined via the 2727275970Scy.Ic setvar 2728275970Scymechanism. 2729275970ScyThere are three special variables that contain the names 2730275970Scyof all variable of the same group. 2731275970ScyThe 2732275970Scy.Va sys_var_list 2733275970Scyholds 2734275970Scythe names of all system variables. 2735275970ScyThe 2736275970Scy.Va peer_var_list 2737275970Scyholds 2738275970Scythe names of all peer variables and the 2739275970Scy.Va clock_var_list 2740275970Scyholds the names of the reference clock variables. 2741275970Scy.It Xo Ic tinker 2742275970Scy.Oo 2743275970Scy.Cm allan Ar allan | 2744275970Scy.Cm dispersion Ar dispersion | 2745275970Scy.Cm freq Ar freq | 2746275970Scy.Cm huffpuff Ar huffpuff | 2747275970Scy.Cm panic Ar panic | 2748285612Sdelphij.Cm step Ar step | 2749285612Sdelphij.Cm stepback Ar stepback | 2750285612Sdelphij.Cm stepfwd Ar stepfwd | 2751275970Scy.Cm stepout Ar stepout 2752275970Scy.Oc 2753275970Scy.Xc 2754275970ScyThis command can be used to alter several system variables in 2755275970Scyvery exceptional circumstances. 2756275970ScyIt should occur in the 2757275970Scyconfiguration file before any other configuration options. 2758275970ScyThe 2759275970Scydefault values of these variables have been carefully optimized for 2760275970Scya wide range of network speeds and reliability expectations. 2761275970ScyIn 2762275970Scygeneral, they interact in intricate ways that are hard to predict 2763275970Scyand some combinations can result in some very nasty behavior. 2764275970ScyVery 2765275970Scyrarely is it necessary to change the default values; but, some 2766275970Scyfolks cannot resist twisting the knobs anyway and this command is 2767275970Scyfor them. 2768275970ScyEmphasis added: twisters are on their own and can expect 2769275970Scyno help from the support group. 2770275970Scy.Pp 2771275970ScyThe variables operate as follows: 2772275970Scy.Bl -tag -width indent 2773275970Scy.It Cm allan Ar allan 2774275970ScyThe argument becomes the new value for the minimum Allan 2775275970Scyintercept, which is a parameter of the PLL/FLL clock discipline 2776275970Scyalgorithm. 2777275970ScyThe value in log2 seconds defaults to 7 (1024 s), which is also the lower 2778275970Scylimit. 2779275970Scy.It Cm dispersion Ar dispersion 2780275970ScyThe argument becomes the new value for the dispersion increase rate, 2781275970Scynormally .000015 s/s. 2782275970Scy.It Cm freq Ar freq 2783275970ScyThe argument becomes the initial value of the frequency offset in 2784275970Scyparts\-per\-million. 2785275970ScyThis overrides the value in the frequency file, if 2786275970Scypresent, and avoids the initial training state if it is not. 2787275970Scy.It Cm huffpuff Ar huffpuff 2788275970ScyThe argument becomes the new value for the experimental 2789275970Scyhuff\-n'\-puff filter span, which determines the most recent interval 2790275970Scythe algorithm will search for a minimum delay. 2791275970ScyThe lower limit is 2792275970Scy900 s (15 m), but a more reasonable value is 7200 (2 hours). 2793275970ScyThere 2794275970Scyis no default, since the filter is not enabled unless this command 2795275970Scyis given. 2796275970Scy.It Cm panic Ar panic 2797275970ScyThe argument is the panic threshold, normally 1000 s. 2798275970ScyIf set to zero, 2799275970Scythe panic sanity check is disabled and a clock offset of any value will 2800275970Scybe accepted. 2801275970Scy.It Cm step Ar step 2802275970ScyThe argument is the step threshold, which by default is 0.128 s. 2803275970ScyIt can 2804275970Scybe set to any positive number in seconds. 2805275970ScyIf set to zero, step 2806275970Scyadjustments will never occur. 2807275970ScyNote: The kernel time discipline is 2808275970Scydisabled if the step threshold is set to zero or greater than the 2809275970Scydefault. 2810285612Sdelphij.It Cm stepback Ar stepback 2811285612SdelphijThe argument is the step threshold for the backward direction, 2812285612Sdelphijwhich by default is 0.128 s. 2813285612SdelphijIt can 2814285612Sdelphijbe set to any positive number in seconds. 2815285612SdelphijIf both the forward and backward step thresholds are set to zero, step 2816285612Sdelphijadjustments will never occur. 2817285612SdelphijNote: The kernel time discipline is 2818285612Sdelphijdisabled if 2819285612Sdelphijeach direction of step threshold are either 2820285612Sdelphijset to zero or greater than .5 second. 2821285612Sdelphij.It Cm stepfwd Ar stepfwd 2822285612SdelphijAs for stepback, but for the forward direction. 2823275970Scy.It Cm stepout Ar stepout 2824275970ScyThe argument is the stepout timeout, which by default is 900 s. 2825275970ScyIt can 2826275970Scybe set to any positive number in seconds. 2827275970ScyIf set to zero, the stepout 2828275970Scypulses will not be suppressed. 2829275970Scy.El 2830275970Scy.It Xo Ic rlimit 2831275970Scy.Oo 2832275970Scy.Cm memlock Ar Nmegabytes | 2833275970Scy.Cm stacksize Ar N4kPages 2834275970Scy.Cm filenum Ar Nfiledescriptors 2835275970Scy.Oc 2836275970Scy.Xc 2837275970Scy.Bl -tag -width indent 2838275970Scy.It Cm memlock Ar Nmegabytes 2839289999SglebiusSpecify the number of megabytes of memory that should be 2840289999Sglebiusallocated and locked. 2841289999SglebiusProbably only available under Linux, this option may be useful 2842275970Scywhen dropping root (the 2843275970Scy.Fl i 2844275970Scyoption). 2845289999SglebiusThe default is 32 megabytes on non\-Linux machines, and \-1 under Linux. 2846289999Sglebius-1 means "do not lock the process into memory". 2847289999Sglebius0 means "lock whatever memory the process wants into memory". 2848275970Scy.It Cm stacksize Ar N4kPages 2849275970ScySpecifies the maximum size of the process stack on systems with the 2850275970Scy.Fn mlockall 2851275970Scyfunction. 2852275970ScyDefaults to 50 4k pages (200 4k pages in OpenBSD). 2853285612Sdelphij.It Cm filenum Ar Nfiledescriptors 2854298770SdelphijSpecifies the maximum number of file descriptors ntpd may have open at once. 2855298770SdelphijDefaults to the system default. 2856275970Scy.El 2857275970Scy.It Xo Ic trap Ar host_address 2858275970Scy.Op Cm port Ar port_number 2859275970Scy.Op Cm interface Ar interface_address 2860275970Scy.Xc 2861275970ScyThis command configures a trap receiver at the given host 2862275970Scyaddress and port number for sending messages with the specified 2863275970Scylocal interface address. 2864275970ScyIf the port number is unspecified, a value 2865275970Scyof 18447 is used. 2866275970ScyIf the interface address is not specified, the 2867275970Scymessage is sent with a source address of the local interface the 2868275970Scymessage is sent through. 2869275970ScyNote that on a multihomed host the 2870275970Scyinterface used may vary from time to time with routing changes. 2871275970Scy.Pp 2872275970ScyThe trap receiver will generally log event messages and other 2873275970Scyinformation from the server in a log file. 2874275970ScyWhile such monitor 2875275970Scyprograms may also request their own trap dynamically, configuring a 2876275970Scytrap receiver will ensure that no messages are lost when the server 2877275970Scyis started. 2878275970Scy.It Cm hop Ar ... 2879275970ScyThis command specifies a list of TTL values in increasing order, up to 8 2880275970Scyvalues can be specified. 2881275970ScyIn manycast mode these values are used in turn in 2882275970Scyan expanding\-ring search. 2883275970ScyThe default is eight multiples of 32 starting at 2884275970Scy31. 2885275970Scy.El 2886275970Scy.Sh "OPTIONS" 2887275970Scy.Bl -tag 2888275970Scy.It Fl \-help 2889275970ScyDisplay usage information and exit. 2890275970Scy.It Fl \-more\-help 2891275970ScyPass the extended usage information through a pager. 2892275970Scy.It Fl \-version Op Brq Ar v|c|n 2893275970ScyOutput version of program and exit. The default mode is `v', a simple 2894275970Scyversion. The `c' mode will print copyright information and `n' will 2895275970Scyprint the full copyright notice. 2896275970Scy.El 2897275970Scy.Sh "OPTION PRESETS" 2898275970ScyAny option that is not marked as \fInot presettable\fP may be preset 2899275970Scyby loading values from environment variables named: 2900275970Scy.nf 2901275970Scy \fBNTP_CONF_<option\-name>\fP or \fBNTP_CONF\fP 2902275970Scy.fi 2903275970Scy.ad 2904275970Scy.Sh "ENVIRONMENT" 2905275970ScySee \fBOPTION PRESETS\fP for configuration environment variables. 2906275970Scy.Sh FILES 2907275970Scy.Bl -tag -width /etc/ntp.drift -compact 2908275970Scy.It Pa /etc/ntp.conf 2909275970Scythe default name of the configuration file 2910275970Scy.It Pa ntp.keys 2911275970Scyprivate MD5 keys 2912275970Scy.It Pa ntpkey 2913275970ScyRSA private key 2914275970Scy.It Pa ntpkey_ Ns Ar host 2915275970ScyRSA public key 2916275970Scy.It Pa ntp_dh 2917275970ScyDiffie\-Hellman agreement parameters 2918275970Scy.El 2919275970Scy.Sh "EXIT STATUS" 2920275970ScyOne of the following exit values will be returned: 2921275970Scy.Bl -tag 2922275970Scy.It 0 " (EXIT_SUCCESS)" 2923275970ScySuccessful program execution. 2924275970Scy.It 1 " (EXIT_FAILURE)" 2925275970ScyThe operation failed or the command syntax was not valid. 2926275970Scy.It 70 " (EX_SOFTWARE)" 2927275970Scylibopts had an internal operational error. Please report 2928275970Scyit to autogen\-users@lists.sourceforge.net. Thank you. 2929275970Scy.El 2930275970Scy.Sh "SEE ALSO" 2931275970Scy.Xr ntpd 1ntpdmdoc , 2932275970Scy.Xr ntpdc 1ntpdcmdoc , 2933275970Scy.Xr ntpq 1ntpqmdoc 2934275970Scy.Pp 2935275970ScyIn addition to the manual pages provided, 2936275970Scycomprehensive documentation is available on the world wide web 2937275970Scyat 2938275970Scy.Li http://www.ntp.org/ . 2939275970ScyA snapshot of this documentation is available in HTML format in 2940275970Scy.Pa /usr/share/doc/ntp . 2941275970Scy.Rs 2942275970Scy.%A David L. Mills 2943275970Scy.%T Network Time Protocol (Version 4) 2944275970Scy.%O RFC5905 2945275970Scy.Re 2946275970Scy.Sh "AUTHORS" 2947280849ScyThe University of Delaware and Network Time Foundation 2948275970Scy.Sh "COPYRIGHT" 2949294904SdelphijCopyright (C) 1992\-2016 The University of Delaware and Network Time Foundation all rights reserved. 2950275970ScyThis program is released under the terms of the NTP license, <http://ntp.org/license>. 2951275970Scy.Sh BUGS 2952275970ScyThe syntax checking is not picky; some combinations of 2953275970Scyridiculous and even hilarious options and modes may not be 2954275970Scydetected. 2955275970Scy.Pp 2956275970ScyThe 2957275970Scy.Pa ntpkey_ Ns Ar host 2958275970Scyfiles are really digital 2959275970Scycertificates. 2960275970ScyThese should be obtained via secure directory 2961275970Scyservices when they become universally available. 2962275970Scy.Pp 2963275970ScyPlease send bug reports to: http://bugs.ntp.org, bugs@ntp.org 2964275970Scy.Sh NOTES 2965275970ScyThis document was derived from FreeBSD. 2966275970Scy.Pp 2967275970ScyThis manual page was \fIAutoGen\fP\-erated from the \fBntp.conf\fP 2968275970Scyoption definitions. 2969