ntpd.man.in revision 294569
1215976Sjmallett.de1 NOP 2232812Sjmallett. it 1 an-trap 3215976Sjmallett. if \\n[.$] \,\\$*\/ 4215976Sjmallett.. 5215976Sjmallett.ie t \ 6215976Sjmallett.ds B-Font [CB] 7215976Sjmallett.ds I-Font [CI] 8215976Sjmallett.ds R-Font [CR] 9215976Sjmallett.el \ 10215976Sjmallett.ds B-Font B 11215976Sjmallett.ds I-Font I 12215976Sjmallett.ds R-Font R 13215976Sjmallett.TH ntpd @NTPD_MS@ "20 Jan 2016" "4.2.8p6" "User Commands" 14215976Sjmallett.\" 15215976Sjmallett.\" EDIT THIS FILE WITH CAUTION (/tmp/.ag-9JaiRS/ag-jKaaQS) 16215976Sjmallett.\" 17215976Sjmallett.\" It has been AutoGen-ed January 20, 2016 at 04:17:54 AM by AutoGen 5.18.5 18232812Sjmallett.\" From the definitions ntpd-opts.def 19215976Sjmallett.\" and the template file agman-cmd.tpl 20215976Sjmallett.SH NAME 21215976Sjmallett\f\*[B-Font]ntpd\fP 22215976Sjmallett\- NTP daemon program 23215976Sjmallett.SH SYNOPSIS 24215976Sjmallett\f\*[B-Font]ntpd\fP 25215976Sjmallett.\" Mixture of short (flag) options and long options 26215976Sjmallett[\f\*[B-Font]\-flags\f[]] 27215976Sjmallett[\f\*[B-Font]\-flag\f[] [\f\*[I-Font]value\f[]]] 28215976Sjmallett[\f\*[B-Font]\-\-option-name\f[][[=| ]\f\*[I-Font]value\f[]]] 29232812Sjmallett[ <server1> ... <serverN> ] 30215976Sjmallett.sp \n(Ppu 31215976Sjmallett.ne 2 32215976Sjmallett 33215976Sjmallett.SH DESCRIPTION 34215976SjmallettThe 35215976Sjmallett\f\*[B-Font]ntpd\fP 36215976Sjmallettutility is an operating system daemon which sets 37215976Sjmallettand maintains the system time of day in synchronism with Internet 38215976Sjmallettstandard time servers. 39215976SjmallettIt is a complete implementation of the 40215976SjmallettNetwork Time Protocol (NTP) version 4, as defined by RFC-5905, 41215976Sjmallettbut also retains compatibility with 42215976Sjmallettversion 3, as defined by RFC-1305, and versions 1 43215976Sjmallettand 2, as defined by RFC-1059 and RFC-1119, respectively. 44215976Sjmallett.sp \n(Ppu 45215976Sjmallett.ne 2 46215976Sjmallett 47215976SjmallettThe 48215976Sjmallett\f\*[B-Font]ntpd\fP 49215976Sjmallettutility does most computations in 64-bit floating point 50215976Sjmallettarithmetic and does relatively clumsy 64-bit fixed point operations 51215976Sjmallettonly when necessary to preserve the ultimate precision, about 232 52232812Sjmallettpicoseconds. 53232812SjmallettWhile the ultimate precision is not achievable with 54215976Sjmallettordinary workstations and networks of today, it may be required 55232812Sjmallettwith future gigahertz CPU clocks and gigabit LANs. 56232812Sjmallett.sp \n(Ppu 57232812Sjmallett.ne 2 58232812Sjmallett 59232812SjmallettOrdinarily, 60232812Sjmallett\f\*[B-Font]ntpd\fP 61232812Sjmallettreads the 62232812Sjmallett\fCntp.conf\f[]\fR(5)\f[] 63232812Sjmallettconfiguration file at startup time in order to determine the 64215976Sjmallettsynchronization sources and operating modes. 65232812SjmallettIt is also possible to 66232812Sjmallettspecify a working, although limited, configuration entirely on the 67232812Sjmallettcommand line, obviating the need for a configuration file. 68232812SjmallettThis may 69232812Sjmallettbe particularly useful when the local host is to be configured as a 70232812Sjmallettbroadcast/multicast client, with all peers being determined by 71232812Sjmallettlistening to broadcasts at run time. 72232812Sjmallett.sp \n(Ppu 73232812Sjmallett.ne 2 74232812Sjmallett 75215976SjmallettIf NetInfo support is built into 76232812Sjmallett\f\*[B-Font]ntpd\fP, 77232812Sjmallettthen 78232812Sjmallett\f\*[B-Font]ntpd\fP 79232812Sjmallettwill attempt to read its configuration from the 80232812SjmallettNetInfo if the default 81232812Sjmallett\fCntp.conf\f[]\fR(5)\f[] 82232812Sjmallettfile cannot be read and no file is 83232812Sjmallettspecified by the 84232812Sjmallett\f\*[B-Font]\-c\f[] 85232812Sjmallettoption. 86215976Sjmallett.sp \n(Ppu 87232812Sjmallett.ne 2 88232812Sjmallett 89232812SjmallettVarious internal 90232812Sjmallett\f\*[B-Font]ntpd\fP 91232812Sjmallettvariables can be displayed and 92232812Sjmallettconfiguration options altered while the 93232812Sjmallett\f\*[B-Font]ntpd\fP 94232812Sjmallettis running 95232812Sjmallettusing the 96232812Sjmallett\fCntpq\f[]\fR(@NTPQ_MS@)\f[] 97215976Sjmallettand 98232812Sjmallett\fCntpdc\f[]\fR(@NTPDC_MS@)\f[] 99215976Sjmallettutility programs. 100215976Sjmallett.sp \n(Ppu 101215976Sjmallett.ne 2 102215976Sjmallett 103215976SjmallettWhen 104215976Sjmallett\f\*[B-Font]ntpd\fP 105215976Sjmallettstarts it looks at the value of 106215976Sjmallett\fCumask\f[]\fR(2)\f[], 107215976Sjmallettand if zero 108215976Sjmallett\f\*[B-Font]ntpd\fP 109215976Sjmallettwill set the 110232812Sjmallett\fCumask\f[]\fR(2)\f[] 111232812Sjmallettto 022. 112232812Sjmallett.SH "OPTIONS" 113232812Sjmallett.TP 114215976Sjmallett.NOP \f\*[B-Font]\-4\f[], \f\*[B-Font]\-\-ipv4\f[] 115215976SjmallettForce IPv4 DNS name resolution. 116215976SjmallettThis option must not appear in combination with any of the following options: 117215976Sjmallettipv6. 118215976Sjmallett.sp 119215976SjmallettForce DNS resolution of following host names on the command line 120232812Sjmallettto the IPv4 namespace. 121232812Sjmallett.TP 122232812Sjmallett.NOP \f\*[B-Font]\-6\f[], \f\*[B-Font]\-\-ipv6\f[] 123232812SjmallettForce IPv6 DNS name resolution. 124232812SjmallettThis option must not appear in combination with any of the following options: 125232812Sjmallettipv4. 126232812Sjmallett.sp 127232812SjmallettForce DNS resolution of following host names on the command line 128232812Sjmallettto the IPv6 namespace. 129215976Sjmallett.TP 130232812Sjmallett.NOP \f\*[B-Font]\-a\f[], \f\*[B-Font]\-\-authreq\f[] 131215976SjmallettRequire crypto authentication. 132215976SjmallettThis option must not appear in combination with any of the following options: 133215976Sjmallettauthnoreq. 134215976Sjmallett.sp 135232812SjmallettRequire cryptographic authentication for broadcast client, 136215976Sjmallettmulticast client and symmetric passive associations. 137215976SjmallettThis is the default. 138215976Sjmallett.TP 139215976Sjmallett.NOP \f\*[B-Font]\-A\f[], \f\*[B-Font]\-\-authnoreq\f[] 140215976SjmallettDo not require crypto authentication. 141215976SjmallettThis option must not appear in combination with any of the following options: 142215976Sjmallettauthreq. 143215976Sjmallett.sp 144215976SjmallettDo not require cryptographic authentication for broadcast client, 145215976Sjmallettmulticast client and symmetric passive associations. 146232812SjmallettThis is almost never a good idea. 147215976Sjmallett.TP 148215976Sjmallett.NOP \f\*[B-Font]\-b\f[], \f\*[B-Font]\-\-bcastsync\f[] 149215976SjmallettAllow us to sync to broadcast servers. 150215976Sjmallett.sp 151215976Sjmallett.TP 152215976Sjmallett.NOP \f\*[B-Font]\-c\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-configfile\f[]=\f\*[I-Font]string\f[] 153215976Sjmallettconfiguration file name. 154215976Sjmallett.sp 155215976SjmallettThe name and path of the configuration file, 156215976Sjmallett\fI/etc/ntp.conf\fP 157215976Sjmallettby default. 158215976Sjmallett.TP 159232812Sjmallett.NOP \f\*[B-Font]\-d\f[], \f\*[B-Font]\-\-debug\-level\f[] 160232812SjmallettIncrease debug verbosity level. 161232812SjmallettThis option may appear an unlimited number of times. 162232812Sjmallett.sp 163215976Sjmallett.TP 164215976Sjmallett.NOP \f\*[B-Font]\-D\f[] \f\*[I-Font]number\f[], \f\*[B-Font]\-\-set\-debug\-level\f[]=\f\*[I-Font]number\f[] 165215976SjmallettSet the debug verbosity level. 166215976SjmallettThis option may appear an unlimited number of times. 167215976SjmallettThis option takes an integer number as its argument. 168215976Sjmallett.sp 169232812Sjmallett.TP 170232812Sjmallett.NOP \f\*[B-Font]\-f\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-driftfile\f[]=\f\*[I-Font]string\f[] 171232812Sjmallettfrequency drift file name. 172232812Sjmallett.sp 173232812SjmallettThe name and path of the frequency file, 174232812Sjmallett\fI/etc/ntp.drift\fP 175232812Sjmallettby default. 176232812SjmallettThis is the same operation as the 177232812Sjmallett\fBdriftfile\fP \fIdriftfile\fP 178215976Sjmallettconfiguration specification in the 179232812Sjmallett\fI/etc/ntp.conf\fP 180232812Sjmallettfile. 181232812Sjmallett.TP 182232812Sjmallett.NOP \f\*[B-Font]\-g\f[], \f\*[B-Font]\-\-panicgate\f[] 183232812SjmallettAllow the first adjustment to be Big. 184232812SjmallettThis option may appear an unlimited number of times. 185232812Sjmallett.sp 186232812SjmallettNormally, 187232812Sjmallett\fBntpd\fP 188232812Sjmallettexits with a message to the system log if the offset exceeds the panic threshold, which is 1000 s by default. This option allows the time to be set to any value without restriction; however, this can happen only once. If the threshold is exceeded after that, 189215976Sjmallett\fBntpd\fP 190232812Sjmallettwill exit with a message to the system log. This option can be used with the 191215976Sjmallett\fB-q\fP 192215976Sjmallettand 193215976Sjmallett\fB-x\fP 194215976Sjmallettoptions. 195232812SjmallettSee the 196215976Sjmallett\fBtinker\fP 197215976Sjmallettconfiguration file directive for other options. 198215976Sjmallett.TP 199215976Sjmallett.NOP \f\*[B-Font]\-G\f[], \f\*[B-Font]\-\-force\-step\-once\f[] 200215976SjmallettStep any initial offset correction.. 201215976Sjmallett.sp 202215976SjmallettNormally, 203215976Sjmallett\fBntpd\fP 204215976Sjmallettsteps the time if the time offset exceeds the step threshold, 205215976Sjmallettwhich is 128 ms by default, and otherwise slews the time. 206215976SjmallettThis option forces the initial offset correction to be stepped, 207215976Sjmallettso the highest time accuracy can be achieved quickly. 208215976SjmallettHowever, this may also cause the time to be stepped back 209215976Sjmallettso this option must not be used if 210215976Sjmallettapplications requiring monotonic time are running. 211215976SjmallettSee the \fBtinker\fP configuration file directive for other options. 212215976Sjmallett.TP 213232812Sjmallett.NOP \f\*[B-Font]\-i\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-jaildir\f[]=\f\*[I-Font]string\f[] 214232812SjmallettJail directory. 215232812Sjmallett.sp 216232812SjmallettChroot the server to the directory 217215976Sjmallett\fIjaildir\fP 218215976Sjmallett. 219215976SjmallettThis option also implies that the server attempts to drop root privileges at startup. 220215976SjmallettYou may need to also specify a 221215976Sjmallett\fB-u\fP 222215976Sjmallettoption. 223215976SjmallettThis option is only available if the OS supports adjusting the clock 224215976Sjmallettwithout full root privileges. 225215976SjmallettThis option is supported under NetBSD (configure with 226215976Sjmallett\fB--enable-clockctl\fP) or Linux (configure with 227215976Sjmallett\fB--enable-linuxcaps\fP) or Solaris (configure with \fB--enable-solarisprivs\fP). 228215976Sjmallett.TP 229215976Sjmallett.NOP \f\*[B-Font]\-I\f[] \f\*[I-Font]iface\f[], \f\*[B-Font]\-\-interface\f[]=\f\*[I-Font]iface\f[] 230215976SjmallettListen on an interface name or address. 231215976SjmallettThis option may appear an unlimited number of times. 232215976Sjmallett.sp 233215976SjmallettOpen the network address given, or all the addresses associated with the 234232812Sjmallettgiven interface name. This option may appear multiple times. This option 235232812Sjmallettalso implies not opening other addresses, except wildcard and localhost. 236232812SjmallettThis option is deprecated. Please consider using the configuration file 237232812Sjmallett\fBinterface\fP command, which is more versatile. 238215976Sjmallett.TP 239215976Sjmallett.NOP \f\*[B-Font]\-k\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-keyfile\f[]=\f\*[I-Font]string\f[] 240215976Sjmallettpath to symmetric keys. 241215976Sjmallett.sp 242215976SjmallettSpecify the name and path of the symmetric key file. 243215976Sjmallett\fI/etc/ntp.keys\fP 244215976Sjmallettis the default. 245215976SjmallettThis is the same operation as the 246215976Sjmallett\fBkeys\fP \fIkeyfile\fP 247215976Sjmallettconfiguration file directive. 248215976Sjmallett.TP 249215976Sjmallett.NOP \f\*[B-Font]\-l\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-logfile\f[]=\f\*[I-Font]string\f[] 250215976Sjmallettpath to the log file. 251215976Sjmallett.sp 252215976SjmallettSpecify the name and path of the log file. 253215976SjmallettThe default is the system log file. 254215976SjmallettThis is the same operation as the 255232812Sjmallett\fBlogfile\fP \fIlogfile\fP 256232812Sjmallettconfiguration file directive. 257232812Sjmallett.TP 258232812Sjmallett.NOP \f\*[B-Font]\-L\f[], \f\*[B-Font]\-\-novirtualips\f[] 259215976SjmallettDo not listen to virtual interfaces. 260215976Sjmallett.sp 261215976SjmallettDo not listen to virtual interfaces, defined as those with 262215976Sjmallettnames containing a colon. This option is deprecated. Please 263215976Sjmallettconsider using the configuration file \fBinterface\fP command, which 264215976Sjmallettis more versatile. 265232812Sjmallett.TP 266232812Sjmallett.NOP \f\*[B-Font]\-M\f[], \f\*[B-Font]\-\-modifymmtimer\f[] 267232812SjmallettModify Multimedia Timer (Windows only). 268232812Sjmallett.sp 269232812SjmallettSet the Windows Multimedia Timer to highest resolution. This 270232812Sjmallettensures the resolution does not change while ntpd is running, 271232812Sjmallettavoiding timekeeping glitches associated with changes. 272232812Sjmallett.TP 273232812Sjmallett.NOP \f\*[B-Font]\-n\f[], \f\*[B-Font]\-\-nofork\f[] 274215976SjmallettDo not fork. 275232812SjmallettThis option must not appear in combination with any of the following options: 276232812Sjmallettwait-sync. 277232812Sjmallett.sp 278232812Sjmallett.TP 279232812Sjmallett.NOP \f\*[B-Font]\-N\f[], \f\*[B-Font]\-\-nice\f[] 280232812SjmallettRun at high priority. 281232812Sjmallett.sp 282232812SjmallettTo the extent permitted by the operating system, run 283232812Sjmallett\fBntpd\fP 284232812Sjmallettat the highest priority. 285215976Sjmallett.TP 286232812Sjmallett.NOP \f\*[B-Font]\-p\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-pidfile\f[]=\f\*[I-Font]string\f[] 287215976Sjmallettpath to the PID file. 288215976Sjmallett.sp 289215976SjmallettSpecify the name and path of the file used to record 290215976Sjmallett\fBntpd\fP's 291215976Sjmallettprocess ID. 292215976SjmallettThis is the same operation as the 293215976Sjmallett\fBpidfile\fP \fIpidfile\fP 294215976Sjmallettconfiguration file directive. 295215976Sjmallett.TP 296215976Sjmallett.NOP \f\*[B-Font]\-P\f[] \f\*[I-Font]number\f[], \f\*[B-Font]\-\-priority\f[]=\f\*[I-Font]number\f[] 297215976SjmallettProcess priority. 298232812SjmallettThis option takes an integer number as its argument. 299232812Sjmallett.sp 300232812SjmallettTo the extent permitted by the operating system, run 301232812Sjmallett\fBntpd\fP 302215976Sjmallettat the specified 303215976Sjmallett\fBsched_setscheduler(SCHED_FIFO)\fP 304215976Sjmallettpriority. 305215976Sjmallett.TP 306215976Sjmallett.NOP \f\*[B-Font]\-q\f[], \f\*[B-Font]\-\-quit\f[] 307215976SjmallettSet the time and quit. 308232812SjmallettThis option must not appear in combination with any of the following options: 309232812Sjmallettsaveconfigquit, wait-sync. 310232812Sjmallett.sp 311232812Sjmallett\fBntpd\fP 312232812Sjmallettwill not daemonize and will exit after the clock is first 313232812Sjmallettsynchronized. This behavior mimics that of the 314232812Sjmallett\fBntpdate\fP 315232812Sjmallettprogram, which will soon be replaced with a shell script. 316232812SjmallettThe 317215976Sjmallett\fB-g\fP 318232812Sjmallettand 319215976Sjmallett\fB-x\fP 320215976Sjmallettoptions can be used with this option. 321215976SjmallettNote: The kernel time discipline is disabled with this option. 322215976Sjmallett.TP 323215976Sjmallett.NOP \f\*[B-Font]\-r\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-propagationdelay\f[]=\f\*[I-Font]string\f[] 324215976SjmallettBroadcast/propagation delay. 325215976Sjmallett.sp 326215976SjmallettSpecify the default propagation delay from the broadcast/multicast server to this client. This is necessary only if the delay cannot be computed automatically by the protocol. 327215976Sjmallett.TP 328215976Sjmallett.NOP \f\*[B-Font]\-\-saveconfigquit\f[]=\f\*[I-Font]string\f[] 329215976SjmallettSave parsed configuration and quit. 330232812SjmallettThis option must not appear in combination with any of the following options: 331232812Sjmallettquit, wait-sync. 332232812Sjmallett.sp 333232812SjmallettCause \fBntpd\fP to parse its startup configuration file and save an 334215976Sjmallettequivalent to the given filename and exit. This option was 335215976Sjmallettdesigned for automated testing. 336215976Sjmallett.TP 337215976Sjmallett.NOP \f\*[B-Font]\-s\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-statsdir\f[]=\f\*[I-Font]string\f[] 338215976SjmallettStatistics file location. 339215976Sjmallett.sp 340232812SjmallettSpecify the directory path for files created by the statistics facility. 341232812SjmallettThis is the same operation as the 342232812Sjmallett\fBstatsdir\fP \fIstatsdir\fP 343232812Sjmallettconfiguration file directive. 344232812Sjmallett.TP 345232812Sjmallett.NOP \f\*[B-Font]\-t\f[] \f\*[I-Font]tkey\f[], \f\*[B-Font]\-\-trustedkey\f[]=\f\*[I-Font]tkey\f[] 346232812SjmallettTrusted key number. 347232812SjmallettThis option may appear an unlimited number of times. 348232812Sjmallett.sp 349215976SjmallettAdd the specified key number to the trusted key list. 350232812Sjmallett.TP 351215976Sjmallett.NOP \f\*[B-Font]\-u\f[] \f\*[I-Font]string\f[], \f\*[B-Font]\-\-user\f[]=\f\*[I-Font]string\f[] 352215976SjmallettRun as userid (or userid:groupid). 353215976Sjmallett.sp 354215976SjmallettSpecify a user, and optionally a group, to switch to. 355215976SjmallettThis option is only available if the OS supports adjusting the clock 356215976Sjmallettwithout full root privileges. 357215976SjmallettThis option is supported under NetBSD (configure with 358215976Sjmallett\fB--enable-clockctl\fP) or Linux (configure with 359215976Sjmallett\fB--enable-linuxcaps\fP) or Solaris (configure with \fB--enable-solarisprivs\fP). 360215976Sjmallett.TP 361215976Sjmallett.NOP \f\*[B-Font]\-U\f[] \f\*[I-Font]number\f[], \f\*[B-Font]\-\-updateinterval\f[]=\f\*[I-Font]number\f[] 362232812Sjmallettinterval in seconds between scans for new or dropped interfaces. 363232812SjmallettThis option takes an integer number as its argument. 364232812Sjmallett.sp 365232812SjmallettGive the time in seconds between two scans for new or dropped interfaces. 366215976SjmallettFor systems with routing socket support the scans will be performed shortly after the interface change 367215976Sjmalletthas been detected by the system. 368215976SjmallettUse 0 to disable scanning. 60 seconds is the minimum time between scans. 369215976Sjmallett.TP 370215976Sjmallett.NOP \f\*[B-Font]\-\-var\f[]=\f\*[I-Font]nvar\f[] 371215976Sjmallettmake ARG an ntp variable (RW). 372215976SjmallettThis option may appear an unlimited number of times. 373215976Sjmallett.sp 374215976Sjmallett.TP 375215976Sjmallett.NOP \f\*[B-Font]\-\-dvar\f[]=\f\*[I-Font]ndvar\f[] 376215976Sjmallettmake ARG an ntp variable (RW|DEF). 377215976SjmallettThis option may appear an unlimited number of times. 378215976Sjmallett.sp 379215976Sjmallett.TP 380215976Sjmallett.NOP \f\*[B-Font]\-w\f[] \f\*[I-Font]number\f[], \f\*[B-Font]\-\-wait\-sync\f[]=\f\*[I-Font]number\f[] 381215976SjmallettSeconds to wait for first clock sync. 382215976SjmallettThis option must not appear in combination with any of the following options: 383232812Sjmallettnofork, quit, saveconfigquit. 384232812SjmallettThis option takes an integer number as its argument. 385232812Sjmallett.sp 386232812SjmallettIf greater than zero, alters \fBntpd\fP's behavior when forking to 387215976Sjmallettdaemonize. Instead of exiting with status 0 immediately after 388215976Sjmallettthe fork, the parent waits up to the specified number of 389215976Sjmallettseconds for the child to first synchronize the clock. The exit 390215976Sjmallettstatus is zero (success) if the clock was synchronized, 391215976Sjmallettotherwise it is \fBETIMEDOUT\fP. 392215976SjmallettThis provides the option for a script starting \fBntpd\fP to easily 393215976Sjmallettwait for the first set of the clock before proceeding. 394215976Sjmallett.TP 395215976Sjmallett.NOP \f\*[B-Font]\-x\f[], \f\*[B-Font]\-\-slew\f[] 396215976SjmallettSlew up to 600 seconds. 397215976Sjmallett.sp 398215976SjmallettNormally, the time is slewed if the offset is less than the step threshold, which is 128 ms by default, and stepped if above the threshold. 399215976SjmallettThis option sets the threshold to 600 s, which is well within the accuracy window to set the clock manually. 400215976SjmallettNote: Since the slew rate of typical Unix kernels is limited to 0.5 ms/s, each second of adjustment requires an amortization interval of 2000 s. 401215976SjmallettThus, an adjustment as much as 600 s will take almost 14 days to complete. 402215976SjmallettThis option can be used with the 403215976Sjmallett\fB-g\fP 404232812Sjmallettand 405215976Sjmallett\fB-q\fP 406232812Sjmallettoptions. 407232812SjmallettSee the 408215976Sjmallett\fBtinker\fP 409215976Sjmallettconfiguration file directive for other options. 410215976SjmallettNote: The kernel time discipline is disabled with this option. 411215976Sjmallett.TP 412215976Sjmallett.NOP \f\*[B-Font]\-\-usepcc\f[] 413215976SjmallettUse CPU cycle counter (Windows only). 414215976Sjmallett.sp 415215976SjmallettAttempt to substitute the CPU counter for \fBQueryPerformanceCounter\fP. 416215976SjmallettThe CPU counter and \fBQueryPerformanceCounter\fP are compared, and if 417232812Sjmallettthey have the same frequency, the CPU counter (RDTSC on x86) is 418232812Sjmallettused directly, saving the overhead of a system call. 419215976Sjmallett.TP 420215976Sjmallett.NOP \f\*[B-Font]\-\-pccfreq\f[]=\f\*[I-Font]string\f[] 421215976SjmallettForce CPU cycle counter use (Windows only). 422215976Sjmallett.sp 423215976SjmallettForce substitution the CPU counter for \fBQueryPerformanceCounter\fP. 424215976SjmallettThe CPU counter (RDTSC on x86) is used unconditionally with the 425215976Sjmallettgiven frequency (in Hz). 426215976Sjmallett.TP 427215976Sjmallett.NOP \f\*[B-Font]\-m\f[], \f\*[B-Font]\-\-mdns\f[] 428215976SjmallettRegister with mDNS as a NTP server. 429215976Sjmallett.sp 430215976SjmallettRegisters as an NTP server with the local mDNS server which allows 431215976Sjmallettthe server to be discovered via mDNS client lookup. 432215976Sjmallett.TP 433215976Sjmallett.NOP \f\*[B-Font]\-\&?\f[], \f\*[B-Font]\-\-help\f[] 434215976SjmallettDisplay usage information and exit. 435215976Sjmallett.TP 436215976Sjmallett.NOP \f\*[B-Font]\-\&!\f[], \f\*[B-Font]\-\-more-help\f[] 437215976SjmallettPass the extended usage information through a pager. 438215976Sjmallett.TP 439215976Sjmallett.NOP \f\*[B-Font]\-\-version\f[] [{\f\*[I-Font]v|c|n\f[]}] 440215976SjmallettOutput version of program and exit. The default mode is `v', a simple 441215976Sjmallettversion. The `c' mode will print copyright information and `n' will 442215976Sjmallettprint the full copyright notice. 443215976Sjmallett.PP 444215976Sjmallett.SH "OPTION PRESETS" 445215976SjmallettAny option that is not marked as \fInot presettable\fP may be preset 446232812Sjmallettby loading values from environment variables named: 447232812Sjmallett.nf 448215976Sjmallett \fBNTPD_<option-name>\fP or \fBNTPD\fP 449215976Sjmallett.fi 450215976Sjmallett.ad 451215976Sjmallett.SH USAGE 452215976Sjmallett.SS "How NTP Operates" 453215976SjmallettThe 454215976Sjmallett\f\*[B-Font]ntpd\fP 455215976Sjmallettutility operates by exchanging messages with 456215976Sjmallettone or more configured servers over a range of designated poll intervals. 457215976SjmallettWhen 458215976Sjmallettstarted, whether for the first or subsequent times, the program 459215976Sjmallettrequires several exchanges from the majority of these servers so 460215976Sjmallettthe signal processing and mitigation algorithms can accumulate and 461215976Sjmallettgroom the data and set the clock. 462215976SjmallettIn order to protect the network 463215976Sjmallettfrom bursts, the initial poll interval for each server is delayed 464215976Sjmallettan interval randomized over a few seconds. 465215976SjmallettAt the default initial poll 466215976Sjmallettinterval of 64s, several minutes can elapse before the clock is 467215976Sjmallettset. 468215976SjmallettThis initial delay to set the clock 469215976Sjmallettcan be safely and dramatically reduced using the 470215976Sjmallett\f\*[B-Font]iburst\f[] 471215976Sjmallettkeyword with the 472215976Sjmallett\f\*[B-Font]server\f[] 473215976Sjmallettconfiguration 474215976Sjmallettcommand, as described in 475232812Sjmallett\fCntp.conf\f[]\fR(5)\f[]. 476232812Sjmallett.sp \n(Ppu 477215976Sjmallett.ne 2 478215976Sjmallett 479215976SjmallettMost operating systems and hardware of today incorporate a 480215976Sjmalletttime-of-year (TOY) chip to maintain the time during periods when 481215976Sjmallettthe power is off. 482215976SjmallettWhen the machine is booted, the chip is used to 483215976Sjmallettinitialize the operating system time. 484215976SjmallettAfter the machine has 485215976Sjmallettsynchronized to a NTP server, the operating system corrects the 486215976Sjmallettchip from time to time. 487215976SjmallettIn the default case, if 488215976Sjmallett\f\*[B-Font]ntpd\fP 489215976Sjmallettdetects that the time on the host 490215976Sjmallettis more than 1000s from the server time, 491215976Sjmallett\f\*[B-Font]ntpd\fP 492215976Sjmallettassumes something must be terribly wrong and the only 493215976Sjmallettreliable action is for the operator to intervene and set the clock 494215976Sjmallettby hand. 495215976Sjmallett(Reasons for this include there is no TOY chip, 496215976Sjmallettor its battery is dead, or that the TOY chip is just of poor quality.) 497215976SjmallettThis causes 498215976Sjmallett\f\*[B-Font]ntpd\fP 499215976Sjmallettto exit with a panic message to 500215976Sjmallettthe system log. 501215976SjmallettThe 502215976Sjmallett\f\*[B-Font]\-g\f[] 503215976Sjmallettoption overrides this check and the 504215976Sjmallettclock will be set to the server time regardless of the chip time 505215976Sjmallett(up to 68 years in the past or future \(em 506215976Sjmallettthis is a limitation of the NTPv4 protocol). 507215976SjmallettHowever, and to protect against broken hardware, such as when the 508232812SjmallettCMOS battery fails or the clock counter becomes defective, once the 509232812Sjmallettclock has been set an error greater than 1000s will cause 510215976Sjmallett\f\*[B-Font]ntpd\fP 511215976Sjmallettto exit anyway. 512215976Sjmallett.sp \n(Ppu 513215976Sjmallett.ne 2 514215976Sjmallett 515215976SjmallettUnder ordinary conditions, 516215976Sjmallett\f\*[B-Font]ntpd\fP 517215976Sjmallettadjusts the clock in 518215976Sjmallettsmall steps so that the timescale is effectively continuous and 519215976Sjmallettwithout discontinuities. 520215976SjmallettUnder conditions of extreme network 521215976Sjmallettcongestion, the roundtrip delay jitter can exceed three seconds and 522215976Sjmallettthe synchronization distance, which is equal to one-half the 523215976Sjmallettroundtrip delay plus error budget terms, can become very large. 524215976SjmallettThe 525215976Sjmallett\f\*[B-Font]ntpd\fP 526215976Sjmallettalgorithms discard sample offsets exceeding 128 ms, 527215976Sjmallettunless the interval during which no sample offset is less than 128 528215976Sjmallettms exceeds 900s. 529215976SjmallettThe first sample after that, no matter what the 530215976Sjmallettoffset, steps the clock to the indicated time. 531215976SjmallettIn practice this 532215976Sjmallettreduces the false alarm rate where the clock is stepped in error to 533215976Sjmalletta vanishingly low incidence. 534215976Sjmallett.sp \n(Ppu 535215976Sjmallett.ne 2 536215976Sjmallett 537215976SjmallettAs the result of this behavior, once the clock has been set it 538232812Sjmallettvery rarely strays more than 128 ms even under extreme cases of 539232812Sjmallettnetwork path congestion and jitter. 540215976SjmallettSometimes, in particular when 541215976Sjmallett\f\*[B-Font]ntpd\fP 542215976Sjmallettis first started without a valid drift file 543215976Sjmalletton a system with a large intrinsic drift 544215976Sjmallettthe error might grow to exceed 128 ms, 545215976Sjmallettwhich would cause the clock to be set backwards 546215976Sjmallettif the local clock time is more than 128 s 547215976Sjmallettin the future relative to the server. 548215976SjmallettIn some applications, this behavior may be unacceptable. 549215976SjmallettThere are several solutions, however. 550215976SjmallettIf the 551215976Sjmallett\f\*[B-Font]\-x\f[] 552215976Sjmallettoption is included on the command line, the clock will 553215976Sjmallettnever be stepped and only slew corrections will be used. 554215976SjmallettBut this choice comes with a cost that 555215976Sjmallettshould be carefully explored before deciding to use 556215976Sjmallettthe 557215976Sjmallett\f\*[B-Font]\-x\f[] 558215976Sjmallettoption. 559215976SjmallettThe maximum slew rate possible is limited 560215976Sjmallettto 500 parts-per-million (PPM) as a consequence of the correctness 561215976Sjmallettprinciples on which the NTP protocol and algorithm design are 562215976Sjmallettbased. 563215976SjmallettAs a result, the local clock can take a long time to 564215976Sjmallettconverge to an acceptable offset, about 2,000 s for each second the 565215976Sjmallettclock is outside the acceptable range. 566215976SjmallettDuring this interval the 567215976Sjmallettlocal clock will not be consistent with any other network clock and 568215976Sjmallettthe system cannot be used for distributed applications that require 569215976Sjmallettcorrectly synchronized network time. 570215976Sjmallett.sp \n(Ppu 571215976Sjmallett.ne 2 572232812Sjmallett 573232812SjmallettIn spite of the above precautions, sometimes when large 574232812Sjmallettfrequency errors are present the resulting time offsets stray 575232812Sjmallettoutside the 128-ms range and an eventual step or slew time 576232812Sjmallettcorrection is required. 577232812SjmallettIf following such a correction the 578232812Sjmallettfrequency error is so large that the first sample is outside the 579232812Sjmallettacceptable range, 580232812Sjmallett\f\*[B-Font]ntpd\fP 581232812Sjmallettenters the same state as when the 582232812Sjmallett\fIntp.drift\f[] 583232812Sjmallettfile is not present. 584232812SjmallettThe intent of this behavior 585232812Sjmallettis to quickly correct the frequency and restore operation to the 586232812Sjmallettnormal tracking mode. 587232812SjmallettIn the most extreme cases 588232812Sjmallett(the host 589232812Sjmallett\f\*[B-Font]time.ien.it\f[] 590232812Sjmallettcomes to mind), there may be occasional 591232812Sjmallettstep/slew corrections and subsequent frequency corrections. 592232812SjmallettIt 593232812Sjmalletthelps in these cases to use the 594232812Sjmallett\f\*[B-Font]burst\f[] 595232812Sjmallettkeyword when 596232812Sjmallettconfiguring the server, but 597232812SjmallettONLY 598232812Sjmallettwhen you have permission to do so from the owner of the target host. 599215976Sjmallett.sp \n(Ppu 600215976Sjmallett.ne 2 601215976Sjmallett 602215976SjmallettFinally, 603215976Sjmallettin the past many startup scripts would run 604215976Sjmallett\fCntpdate\f[]\fR(@NTPDATE_MS@)\f[] 605215976Sjmallettor 606215976Sjmallett\fCsntp\f[]\fR(@SNTP_MS@)\f[] 607215976Sjmallettto get the system clock close to correct before starting 608215976Sjmallett\fCntpd\f[]\fR(@NTPD_MS@)\f[], 609215976Sjmallettbut this was never more than a mediocre hack and is no longer needed. 610215976SjmallettIf you are following the instructions in 611215976Sjmallett\fIStarting NTP (Best Current Practice)\f[] 612215976Sjmallettand you still need to set the system time before starting 613215976Sjmallett\f\*[B-Font]ntpd\fP, 614215976Sjmallettplease open a bug report and document what is going on, 615215976Sjmallettand then look at using 616215976Sjmallett\fCsntp\f[]\fR(@SNTP_MS@)\f[] 617215976Sjmallettif you really need to set the clock before starting 618215976Sjmallett\f\*[B-Font]ntpd\fP. 619215976Sjmallett.sp \n(Ppu 620215976Sjmallett.ne 2 621215976Sjmallett 622215976SjmallettThere is a way to start 623232812Sjmallett\fCntpd\f[]\fR(@NTPD_MS@)\f[] 624232812Sjmallettthat often addresses all of the problems mentioned above. 625232812Sjmallett.SS "Starting NTP (Best Current Practice)" 626232812SjmallettFirst, use the 627232812Sjmallett\f\*[B-Font]iburst\f[] 628232812Sjmallettoption on your 629232812Sjmallett\f\*[B-Font]server\f[] 630232812Sjmallettentries. 631232812Sjmallett.sp \n(Ppu 632232812Sjmallett.ne 2 633232812Sjmallett 634232812SjmallettIf you can also keep a good 635232812Sjmallett\fIntp.drift\f[] 636232812Sjmallettfile then 637232812Sjmallett\fCntpd\f[]\fR(@NTPD_MS@)\f[] 638232812Sjmallettwill effectively "warm-start" and your system's clock will 639232812Sjmallettbe stable in under 11 seconds' time. 640232812Sjmallett.sp \n(Ppu 641232812Sjmallett.ne 2 642232812Sjmallett 643232812SjmallettAs soon as possible in the startup sequence, start 644232812Sjmallett\fCntpd\f[]\fR(@NTPD_MS@)\f[] 645232812Sjmallettwith at least the 646232812Sjmallett\f\*[B-Font]\-g\f[] 647232812Sjmallettand perhaps the 648232812Sjmallett\f\*[B-Font]\-N\f[] 649215976Sjmallettoptions. 650215976SjmallettThen, 651215976Sjmallettstart the rest of your "normal" processes. 652215976SjmallettThis will give 653215976Sjmallett\fCntpd\f[]\fR(@NTPD_MS@)\f[] 654215976Sjmallettas much time as possible to get the system's clock synchronized and stable. 655215976Sjmallett.sp \n(Ppu 656215976Sjmallett.ne 2 657215976Sjmallett 658215976SjmallettFinally, 659232812Sjmallettif you have processes like 660215976Sjmallett\f\*[B-Font]dovecot\f[] 661232812Sjmallettor database servers 662232812Sjmallettthat require 663215976Sjmallettmonotonically-increasing time, 664215976Sjmallettrun 665215976Sjmallett\fCntp-wait\f[]\fR(@NTP_WAIT_MS@)\f[] 666215976Sjmallettas late as possible in the boot sequence 667215976Sjmallett(perhaps with the 668215976Sjmallett\f\*[B-Font]\-v\f[] 669215976Sjmallettflag) 670215976Sjmallettand after 671215976Sjmallett\fCntp-wait\f[]\fR(@NTP_WAIT_MS@)\f[] 672215976Sjmallettexits successfully 673215976Sjmallettit is as safe as it will ever be to start any process that require 674215976Sjmallettstable time. 675215976Sjmallett.SS "Frequency Discipline" 676215976SjmallettThe 677215976Sjmallett\f\*[B-Font]ntpd\fP 678215976Sjmallettbehavior at startup depends on whether the 679215976Sjmallettfrequency file, usually 680215976Sjmallett\fIntp.drift\f[], 681232812Sjmallettexists. 682215976SjmallettThis file 683215976Sjmallettcontains the latest estimate of clock frequency error. 684232812SjmallettWhen the 685232812Sjmallett\f\*[B-Font]ntpd\fP 686215976Sjmallettis started and the file does not exist, the 687215976Sjmallett\f\*[B-Font]ntpd\fP 688215976Sjmallettenters a special mode designed to quickly adapt to 689215976Sjmallettthe particular system clock oscillator time and frequency error. 690215976SjmallettThis takes approximately 15 minutes, after which the time and 691215976Sjmallettfrequency are set to nominal values and the 692215976Sjmallett\f\*[B-Font]ntpd\fP 693215976Sjmallettenters 694215976Sjmallettnormal mode, where the time and frequency are continuously tracked 695215976Sjmallettrelative to the server. 696215976SjmallettAfter one hour the frequency file is 697215976Sjmallettcreated and the current frequency offset written to it. 698215976SjmallettWhen the 699215976Sjmallett\f\*[B-Font]ntpd\fP 700215976Sjmallettis started and the file does exist, the 701215976Sjmallett\f\*[B-Font]ntpd\fP 702215976Sjmallettfrequency is initialized from the file and enters normal mode 703215976Sjmallettimmediately. 704215976SjmallettAfter that the current frequency offset is written to 705215976Sjmallettthe file at hourly intervals. 706215976Sjmallett.SS "Operating Modes" 707215976SjmallettThe 708215976Sjmallett\f\*[B-Font]ntpd\fP 709215976Sjmallettutility can operate in any of several modes, including 710215976Sjmallettsymmetric active/passive, client/server broadcast/multicast and 711215976Sjmallettmanycast, as described in the 712215976Sjmallett"Association Management" 713215976Sjmallettpage 714215976Sjmallett(available as part of the HTML documentation 715215976Sjmallettprovided in 716215976Sjmallett\fI/usr/share/doc/ntp\f[]). 717215976SjmallettIt normally operates continuously while 718215976Sjmallettmonitoring for small changes in frequency and trimming the clock 719215976Sjmallettfor the ultimate precision. 720232812SjmallettHowever, it can operate in a one-time 721215976Sjmallettmode where the time is set from an external server and frequency is 722232812Sjmallettset from a previously recorded frequency file. 723232812SjmallettA 724215976Sjmallettbroadcast/multicast or manycast client can discover remote servers, 725215976Sjmallettcompute server-client propagation delay correction factors and 726215976Sjmallettconfigure itself automatically. 727215976SjmallettThis makes it possible to deploy a 728215976Sjmallettfleet of workstations without specifying configuration details 729215976Sjmallettspecific to the local environment. 730215976Sjmallett.sp \n(Ppu 731215976Sjmallett.ne 2 732215976Sjmallett 733215976SjmallettBy default, 734215976Sjmallett\f\*[B-Font]ntpd\fP 735215976Sjmallettruns in continuous mode where each of 736215976Sjmallettpossibly several external servers is polled at intervals determined 737215976Sjmallettby an intricate state machine. 738215976SjmallettThe state machine measures the 739215976Sjmallettincidental roundtrip delay jitter and oscillator frequency wander 740215976Sjmallettand determines the best poll interval using a heuristic algorithm. 741215976SjmallettOrdinarily, and in most operating environments, the state machine 742215976Sjmallettwill start with 64s intervals and eventually increase in steps to 743215976Sjmallett1024s. 744215976SjmallettA small amount of random variation is introduced in order to 745215976Sjmallettavoid bunching at the servers. 746215976SjmallettIn addition, should a server become 747215976Sjmallettunreachable for some time, the poll interval is increased in steps 748215976Sjmallettto 1024s in order to reduce network overhead. 749215976Sjmallett.sp \n(Ppu 750215976Sjmallett.ne 2 751215976Sjmallett 752215976SjmallettIn some cases it may not be practical for 753215976Sjmallett\f\*[B-Font]ntpd\fP 754232812Sjmallettto run continuously. 755232812SjmallettA common workaround has been to run the 756215976Sjmallett\fCntpdate\f[]\fR(@NTPDATE_MS@)\f[] 757215976Sjmallettor 758215976Sjmallett\fCsntp\f[]\fR(@SNTP_MS@)\f[] 759215976Sjmallettprograms from a 760215976Sjmallett\fCcron\f[]\fR(8)\f[] 761215976Sjmallettjob at designated 762215976Sjmalletttimes. 763215976SjmallettHowever, these programs do not have the crafted signal 764215976Sjmallettprocessing, error checking or mitigation algorithms of 765215976Sjmallett\f\*[B-Font]ntpd\fP. 766215976SjmallettThe 767215976Sjmallett\f\*[B-Font]\-q\f[] 768215976Sjmallettoption is intended for this purpose. 769215976SjmallettSetting this option will cause 770215976Sjmallett\f\*[B-Font]ntpd\fP 771215976Sjmallettto exit just after 772215976Sjmallettsetting the clock for the first time. 773215976SjmallettThe procedure for initially 774215976Sjmallettsetting the clock is the same as in continuous mode; most 775215976Sjmallettapplications will probably want to specify the 776215976Sjmallett\f\*[B-Font]iburst\f[] 777215976Sjmallettkeyword with the 778215976Sjmallett\f\*[B-Font]server\f[] 779215976Sjmallettconfiguration command. 780215976SjmallettWith this 781215976Sjmallettkeyword a volley of messages are exchanged to groom the data and 782215976Sjmallettthe clock is set in about 10 s. 783215976SjmallettIf nothing is heard after a 784215976Sjmallettcouple of minutes, the daemon times out and exits. 785215976SjmallettAfter a suitable 786232812Sjmallettperiod of mourning, the 787215976Sjmallett\fCntpdate\f[]\fR(@NTPDATE_MS@)\f[] 788215976Sjmallettprogram will be 789232812Sjmallettretired. 790232812Sjmallett.sp \n(Ppu 791215976Sjmallett.ne 2 792215976Sjmallett 793215976SjmallettWhen kernel support is available to discipline the clock 794215976Sjmallettfrequency, which is the case for stock Solaris, Tru64, Linux and 795215976SjmallettFreeBSD, 796215976Sjmalletta useful feature is available to discipline the clock 797215976Sjmallettfrequency. 798215976SjmallettFirst, 799215976Sjmallett\f\*[B-Font]ntpd\fP 800215976Sjmallettis run in continuous mode with 801215976Sjmallettselected servers in order to measure and record the intrinsic clock 802215976Sjmallettfrequency offset in the frequency file. 803215976SjmallettIt may take some hours for 804215976Sjmallettthe frequency and offset to settle down. 805215976SjmallettThen the 806232812Sjmallett\f\*[B-Font]ntpd\fP 807215976Sjmallettis 808232812Sjmallettstopped and run in one-time mode as required. 809232812SjmallettAt each startup, the 810215976Sjmallettfrequency is read from the file and initializes the kernel 811215976Sjmallettfrequency. 812215976Sjmallett.SS "Poll Interval Control" 813215976SjmallettThis version of NTP includes an intricate state machine to 814215976Sjmallettreduce the network load while maintaining a quality of 815215976Sjmallettsynchronization consistent with the observed jitter and wander. 816215976SjmallettThere are a number of ways to tailor the operation in order enhance 817215976Sjmallettaccuracy by reducing the interval or to reduce network overhead by 818215976Sjmallettincreasing it. 819215976SjmallettHowever, the user is advised to carefully consider 820215976Sjmallettthe consequences of changing the poll adjustment range from the 821215976Sjmallettdefault minimum of 64 s to the default maximum of 1,024 s. 822215976SjmallettThe 823215976Sjmallettdefault minimum can be changed with the 824215976Sjmallett\f\*[B-Font]tinker\f[] 825215976Sjmallett\f\*[B-Font]minpoll\f[] 826215976Sjmallettcommand to a value not less than 16 s. 827215976SjmallettThis value is used for all 828215976Sjmallettconfigured associations, unless overridden by the 829215976Sjmallett\f\*[B-Font]minpoll\f[] 830232812Sjmallettoption on the configuration command. 831215976SjmallettNote that most device drivers 832215976Sjmallettwill not operate properly if the poll interval is less than 64 s 833232812Sjmallettand that the broadcast server and manycast client associations will 834232812Sjmallettalso use the default, unless overridden. 835215976Sjmallett.sp \n(Ppu 836215976Sjmallett.ne 2 837215976Sjmallett 838215976SjmallettIn some cases involving dial up or toll services, it may be 839215976Sjmallettuseful to increase the minimum interval to a few tens of minutes 840215976Sjmallettand maximum interval to a day or so. 841215976SjmallettUnder normal operation 842215976Sjmallettconditions, once the clock discipline loop has stabilized the 843215976Sjmallettinterval will be increased in steps from the minimum to the 844215976Sjmallettmaximum. 845232812SjmallettHowever, this assumes the intrinsic clock frequency error 846215976Sjmallettis small enough for the discipline loop correct it. 847232812SjmallettThe capture 848232812Sjmallettrange of the loop is 500 PPM at an interval of 64s decreasing by a 849215976Sjmallettfactor of two for each doubling of interval. 850215976SjmallettAt a minimum of 1,024 851215976Sjmalletts, for example, the capture range is only 31 PPM. 852215976SjmallettIf the intrinsic 853215976Sjmalletterror is greater than this, the drift file 854215976Sjmallett\fIntp.drift\f[] 855215976Sjmallettwill 856215976Sjmalletthave to be specially tailored to reduce the residual error below 857215976Sjmallettthis limit. 858215976SjmallettOnce this is done, the drift file is automatically 859215976Sjmallettupdated once per hour and is available to initialize the frequency 860215976Sjmalletton subsequent daemon restarts. 861215976Sjmallett.SS "The huff-n'-puff Filter" 862215976SjmallettIn scenarios where a considerable amount of data are to be 863215976Sjmallettdownloaded or uploaded over telephone modems, timekeeping quality 864215976Sjmallettcan be seriously degraded. 865215976SjmallettThis occurs because the differential 866215976Sjmallettdelays on the two directions of transmission can be quite large. 867232812SjmallettIn 868215976Sjmallettmany cases the apparent time errors are so large as to exceed the 869215976Sjmallettstep threshold and a step correction can occur during and after the 870232812Sjmallettdata transfer is in progress. 871232812Sjmallett.sp \n(Ppu 872215976Sjmallett.ne 2 873215976Sjmallett 874215976SjmallettThe huff-n'-puff filter is designed to correct the apparent time 875215976Sjmallettoffset in these cases. 876215976SjmallettIt depends on knowledge of the propagation 877215976Sjmallettdelay when no other traffic is present. 878215976SjmallettIn common scenarios this 879215976Sjmallettoccurs during other than work hours. 880215976SjmallettThe filter maintains a shift 881215976Sjmallettregister that remembers the minimum delay over the most recent 882232812Sjmallettinterval measured usually in hours. 883215976SjmallettUnder conditions of severe 884232812Sjmallettdelay, the filter corrects the apparent offset using the sign of 885232812Sjmallettthe offset and the difference between the apparent delay and 886215976Sjmallettminimum delay. 887215976SjmallettThe name of the filter reflects the negative (huff) 888215976Sjmallettand positive (puff) correction, which depends on the sign of the 889215976Sjmallettoffset. 890215976Sjmallett.sp \n(Ppu 891215976Sjmallett.ne 2 892215976Sjmallett 893215976SjmallettThe filter is activated by the 894215976Sjmallett\f\*[B-Font]tinker\f[] 895215976Sjmallettcommand and 896215976Sjmallett\f\*[B-Font]huffpuff\f[] 897215976Sjmallettkeyword, as described in 898215976Sjmallett\fCntp.conf\f[]\fR(5)\f[]. 899215976Sjmallett.SH "ENVIRONMENT" 900215976SjmallettSee \fBOPTION PRESETS\fP for configuration environment variables. 901215976Sjmallett.SH FILES 902215976Sjmallett.TP 15 903215976Sjmallett.NOP \fI/etc/ntp.conf\f[] 904232812Sjmallettthe default name of the configuration file 905215976Sjmallett.br 906215976Sjmallett.ns 907232812Sjmallett.TP 15 908232812Sjmallett.NOP \fI/etc/ntp.drift\f[] 909215976Sjmallettthe default name of the drift file 910215976Sjmallett.br 911215976Sjmallett.ns 912215976Sjmallett.TP 15 913215976Sjmallett.NOP \fI/etc/ntp.keys\f[] 914215976Sjmallettthe default name of the key file 915215976Sjmallett.PP 916215976Sjmallett.SH "EXIT STATUS" 917215976SjmallettOne of the following exit values will be returned: 918215976Sjmallett.TP 919215976Sjmallett.NOP 0 " (EXIT_SUCCESS)" 920232812SjmallettSuccessful program execution. 921215976Sjmallett.TP 922232812Sjmallett.NOP 1 " (EXIT_FAILURE)" 923232812SjmallettThe operation failed or the command syntax was not valid. 924215976Sjmallett.TP 925215976Sjmallett.NOP 70 " (EX_SOFTWARE)" 926215976Sjmallettlibopts had an internal operational error. Please report 927215976Sjmallettit to autogen-users@lists.sourceforge.net. Thank you. 928215976Sjmallett.PP 929215976Sjmallett.SH "SEE ALSO" 930215976Sjmallett\fCntp.conf\f[]\fR(5)\f[], 931215976Sjmallett\fCntpdate\f[]\fR(@NTPDATE_MS@)\f[], 932215976Sjmallett\fCntpdc\f[]\fR(@NTPDC_MS@)\f[], 933215976Sjmallett\fCntpq\f[]\fR(@NTPQ_MS@)\f[], 934215976Sjmallett\fCsntp\f[]\fR(@SNTP_MS@)\f[] 935232812Sjmallett.sp \n(Ppu 936215976Sjmallett.ne 2 937215976Sjmallett 938232812SjmallettIn addition to the manual pages provided, 939232812Sjmallettcomprehensive documentation is available on the world wide web 940215976Sjmallettat 941215976Sjmallett\f[C]http://www.ntp.org/\f[]. 942215976SjmallettA snapshot of this documentation is available in HTML format in 943215976Sjmallett\fI/usr/share/doc/ntp\f[]. 944215976SjmallettDavid L. Mills, 945215976Sjmallett\fINetwork Time Protocol (Version 1)\fR, 946215976SjmallettRFC1059 947215976Sjmallett.PP 948215976Sjmallett 949215976SjmallettDavid L. Mills, 950232812Sjmallett\fINetwork Time Protocol (Version 2)\fR, 951215976SjmallettRFC1119 952232812Sjmallett.PP 953232812Sjmallett 954215976SjmallettDavid L. Mills, 955215976Sjmallett\fINetwork Time Protocol (Version 3)\fR, 956215976SjmallettRFC1305 957215976Sjmallett.PP 958215976Sjmallett 959215976SjmallettDavid L. Mills and J. Martin, Ed. and J. Burbank and W. Kasch, 960215976Sjmallett\fINetwork Time Protocol Version 4: Protocol and Algorithms Specification\fR, 961215976SjmallettRFC5905 962215976Sjmallett.PP 963215976Sjmallett 964215976SjmallettDavid L. Mills and B. Haberman, Ed., 965232812Sjmallett\fINetwork Time Protocol Version 4: Autokey Specification\fR, 966215976SjmallettRFC5906 967215976Sjmallett.PP 968232812Sjmallett 969232812SjmallettH. Gerstung and C. Elliott and B. Haberman, Ed., 970215976Sjmallett\fIDefinitions of Managed Objects for Network Time Protocol Version 4: (NTPv4)\fR, 971215976SjmallettRFC5907 972215976Sjmallett.PP 973215976Sjmallett 974215976SjmallettR. Gayraud and B. Lourdelet, 975215976Sjmallett\fINetwork Time Protocol (NTP) Server Option for DHCPv6\fR, 976215976SjmallettRFC5908 977215976Sjmallett.PP 978215976Sjmallett 979215976Sjmallett.SH "AUTHORS" 980232812SjmallettThe University of Delaware and Network Time Foundation 981215976Sjmallett.SH "COPYRIGHT" 982232812SjmallettCopyright (C) 1992-2016 The University of Delaware and Network Time Foundation all rights reserved. 983232812SjmallettThis program is released under the terms of the NTP license, <http://ntp.org/license>. 984215976Sjmallett.SH BUGS 985215976SjmallettThe 986215976Sjmallett\f\*[B-Font]ntpd\fP 987215976Sjmallettutility has gotten rather fat. 988215976SjmallettWhile not huge, it has gotten 989215976Sjmallettlarger than might be desirable for an elevated-priority 990215976Sjmallett\f\*[B-Font]ntpd\fP 991215976Sjmallettrunning on a workstation, particularly since many of 992215976Sjmallettthe fancy features which consume the space were designed more with 993215976Sjmalletta busy primary server, rather than a high stratum workstation in 994215976Sjmallettmind. 995232812Sjmallett.sp \n(Ppu 996215976Sjmallett.ne 2 997215976Sjmallett 998232812SjmallettPlease send bug reports to: http://bugs.ntp.org, bugs@ntp.org 999232812Sjmallett.SH NOTES 1000215976SjmallettPortions of this document came from FreeBSD. 1001215976Sjmallett.sp \n(Ppu 1002215976Sjmallett.ne 2 1003215976Sjmallett 1004215976SjmallettThis manual page was \fIAutoGen\fP-erated from the \fBntpd\fP 1005215976Sjmallettoption definitions. 1006215976Sjmallett