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23 .TH "ntpd" "1M" "" "" "System Administration Commands" |
23 .TH "ntpd" "1M" "" "" "System Administration Commands" |
24 .SH NAME |
24 .SH NAME |
25 ntpd \- Network Time Protocol daemon Version 4 |
25 ntpd \- Network Time Protocol daemon Version 4 |
26 .SH SYNOPSIS |
26 .SH SYNOPSIS |
35 .SH DESCRIPTION |
35 .SH DESCRIPTION |
36 The \fBntpd\fR program is an operating system daemon that synchronises the system clock with remote NTP time servers or local reference clocks. It is a complete implementation of the Network Time Protocol (\fBNTP\fR) version 4, but also retains compatibility with version 3, as defined by \fIRFC 1305\fR, and versions 1 and 2, as defined by \fIRFC 1059\fR and \fIRFC 1119\fR, respectively. |
36 The \fBntpd\fR program is an operating system daemon that synchronises the system clock with remote NTP time servers or local reference clocks. It is a complete implementation of the Network Time Protocol (\fBNTP\fR) version 4, but also retains compatibility with version 3, as defined by \fIRFC 1305\fR, and versions 1 and 2, as defined by \fIRFC 1059\fR and \fIRFC 1119\fR, respectively. |
37 .SS How \fBNTP\fR Operates |
37 .SS How \fBNTP\fR Operates |
38 The \fBntpd\fR program operates by exchanging messages with one or more configured servers at designated intervals ranging from about one minute to about 17 minutes. When started, the program requires several exchanges while the algorithms accumulate and groom the data before setting the clock. The initial delay to set the clock can be reduced using options as described in the server options page at file:///usr/share/doc/ntp/confopt.html. |
38 The \fBntpd\fR program operates by exchanging messages with one or more configured servers at designated intervals ranging from about one minute to about 17 minutes. When started, the program requires several exchanges while the algorithms accumulate and groom the data before setting the clock. The initial delay to set the clock can be reduced using options as described in the server options page at file:///usr/share/doc/ntp/confopt.html. |
39 .LP |
39 .LP |
40 When the machine is booted, the hardware time of day (TOD) chip is used to initialize the operating system time. After the machine has synchronized to a \fBNTP\fR server, the operating system corrects the chip from time to time. During the course of operation if for some reason the system time is more than 1000s offset from the server time, \fBntpd\fR assumes something must be terribly wrong and exits with a panic message to the system log. If it was started via SMF, the ntp service is placed into maintainance mode and must be cleared manually. The -g option overrides this check at startup and allows \fBntpd\fR to set the clock to the server time regardless of the chip time, but only once. |
40 When the machine is booted, the hardware time of day (TOD) chip is used to initialize the operating system time. After the machine has synchronized to a \fBNTP\fR server, the operating system corrects the chip from time to time. During the course of operation if for some reason the system time is more than 1000s offset from the server time, \fBntpd\fR assumes something must be terribly wrong and exits with a panic message to the system log. If it was started via SMF, the ntp service is placed into maintenance mode and must be cleared manually. The -g option overrides this check at startup and allows \fBntpd\fR to set the clock to the server time regardless of the chip time, but only once. |
41 .LP |
41 .LP |
42 Under ordinary conditions, \fBntpd\fR slews the clock so that the time is effectively continuous and never runs backwards. If due to extreme network congestion an error spike exceeds the \fIstep threshold\fR (128ms by default), the spike is discarded. However, if the error persists for more than the \fIstepout threshold\fR (900s by default) the system clock is stepped to the correct value. In practice the need for a step is extremely rare and almost always the result of a hardware failure. With the -x option the step threshold is increased to 600s. Other options are available using the \fItinker\fR command as described in the miscellaneous options page at file:///usr/share/doc/ntp/miscopt.html. |
42 Under ordinary conditions, \fBntpd\fR slews the clock so that the time is effectively continuous and never runs backwards. If due to extreme network congestion an error spike exceeds the \fIstep threshold\fR (128ms by default), the spike is discarded. However, if the error persists for more than the \fIstepout threshold\fR (900s by default) the system clock is stepped to the correct value. In practice the need for a step is extremely rare and almost always the result of a hardware failure. With the -x option the step threshold is increased to 600s. Other options are available using the \fItinker\fR command as described in the miscellaneous options page at file:///usr/share/doc/ntp/miscopt.html. |
43 .LP |
43 .LP |
44 The issues should be carefully considered before using these options. The maximum slew rate possible is limited to 500 parts-per-million (PPM) by the Unix kernel. As a result, the clock can take 2000s for each second the clock is outside the acceptable range. During this interval the clock will not be consistent with any other network clock and the system cannot be used for distributed applications that require correctly synchronized network time. |
44 The issues should be carefully considered before using these options. The maximum slew rate possible is limited to 500 parts-per-million (PPM) by the Unix kernel. As a result, the clock can take 2000s for each second the clock is outside the acceptable range. During this interval the clock will not be consistent with any other network clock and the system cannot be used for distributed applications that require correctly synchronized network time. |
45 .LP |
45 .LP |
247 the configuration files. The option-name should be in all capital letters. |
247 the configuration files. The option-name should be in all capital letters. |
248 For example, to set the --quit option, you would set the NTPD_QUIT environment |
248 For example, to set the --quit option, you would set the NTPD_QUIT environment |
249 variable. |
249 variable. |
250 .SH AUTOMATIC SERVICE MANAGEMENT (SMF) |
250 .SH AUTOMATIC SERVICE MANAGEMENT (SMF) |
251 \fBNTP\fR on Solaris is managed via the service management facility described in |
251 \fBNTP\fR on Solaris is managed via the service management facility described in |
252 \fBsmf\fR(5). There are several options controlled by services properties which |
252 \fBsmf\fR(5). There are several options controlled by services properties which |
253 can be set by the system administrator. The available options can be listed by |
253 can be set by the system administrator. The available options can be listed by |
254 executing the following command: |
254 executing the following command: |
255 .nf |
255 .nf |
256 svccfg -s svc:/network/ntp:default listprop config |
256 svccfg -s svc:/network/ntp:default listprop config |
257 .fi |
257 .fi |