diff options
Diffstat (limited to 'debian/man/ntpdate.8')
-rw-r--r-- | debian/man/ntpdate.8 | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/debian/man/ntpdate.8 b/debian/man/ntpdate.8 new file mode 100644 index 0000000..7edd018 --- /dev/null +++ b/debian/man/ntpdate.8 @@ -0,0 +1,151 @@ +.TH ntpdate 8 +.SH NAME +ntpdate \- set the date and time via NTP +.SH SYNOPSIS +.B ntpdate +.RB [\| \-bBdoqsuv \|] +.RB [\| \-a +.IR key \|] +.RB [\| \-e +.IR authdelay \|] +.RB [\| \-k +.IR keyfile \|] +.RB [\| \-o +.IR version \|] +.RB [\| \-p +.IR samples \|] +.RB [\| \-t +.IR timeout \|] +.IR server +.RB [\| ... \|] +.SH DESCRIPTION +.B ntpdate +sets the local date and time by polling the Network Time +Protocol (NTP) server(s) given as the +.I server +arguments to determine +the correct time. It must be run as root on the local host. A number +of samples are obtained from each of the servers specified and a +subset of the NTP clock filter and selection algorithms are applied to +select the best of these. Note that the accuracy and reliability of +ntpdate depends on the number of servers, the number of polls each +time it is run and the interval between runs. + +ntpdate can be run manually as necessary to set the host clock, or it +can be run from the host startup script to set the clock at boot time. +This is useful in some cases to set the clock initially before +starting the NTP daemon ntpd. It is also possible to run ntpdate from +a cron script. However, it is important to note that ntpdate with +contrived cron scripts is no substitute for the NTP daemon, which uses +sophisticated algorithms to maximize accuracy and reliability while +minimizing resource use. Finally, since ntpdate does not discipline +the host clock frequency as does ntpd, the accuracy using ntpdate is +limited. + +Time adjustments are made by ntpdate in one of two ways. If ntpdate +determines the clock is in error more than 0.5 second it will simply +step the time by calling the system settimeofday() routine. If the +error is less than 0.5 seconds, it will slew the time by calling the +system adjtime() routine. The latter technique is less disruptive and +more accurate when the error is small, and works quite well when +ntpdate is run by cron every hour or two. + +ntpdate will decline to set the date if an NTP server daemon (e.g., +ntpd) is running on the same host. When running ntpdate on a regular +basis from cron as an alternative to running a daemon, doing so once +every hour or two will result in precise enough timekeeping to avoid +stepping the clock. +.SH OPTIONS +.TP +.BI \-a \ key +Enable the authentication function and specify the key +identifier to be used for authentication as the argument +keyntpdate. The keys and key identifiers must match in both the +client and server key files. The default is to disable the +authentication function. +.TP +.B \-B +Force the time to always be slewed using the adjtime() system +call, even if the measured offset is greater than +-128 ms. The +default is to step the time using settimeofday() if the offset +is greater than +-128 ms. Note that, if the offset is much +greater than +-128 ms in this case, that it can take a long +time (hours) to slew the clock to the correct value. During +this time. the host should not be used to synchronize clients. +.TP +.B \-b +Force the time to be stepped using the settimeofday() system +call, rather than slewed (default) using the adjtime() system +call. This option should be used when called from a startup +file at boot time. +.TP +.B \-d +Enable the debugging mode, in which ntpdate will go through all +the steps, but not adjust the local clock. Information useful +for general debugging will also be printed. +.TP +.BI \-e \ authdelay +Specify the processing delay to perform an authentication +function as the value authdelay, in seconds and fraction (see +ntpd for details). This number is usually small enough to be +negligible for most purposes, though specifying a value may +improve timekeeping on very slow CPU's. +.TP +.BI \-k \ keyfile +Specify the path for the authentication key file as the string +keyfile. The default is /etc/ntp.keys. This file should be in +the format described in ntpd. +.TP +.BI \-o \ version +Specify the NTP version for outgoint packets as the integer +version, which can be 1 or 2. The default is 3. This allows +ntpdate to be used with older NTP versions. +.TP +.BI \-p \ samples +Specify the number of samples to be acquired from each server +as the integer samples, with values from 1 to 8 inclusive. The +default is 4. +.TP +.B \-q +Query only - don't set the clock. +.TP +.B \-s +Divert logging output from the standard output (default) to the +system syslog facility. This is designed primarily for +convenience of cron scripts. +.TP +.BI \-t \ timeout +Specify the maximum time waiting for a server response as the +value timeout, in seconds and fraction. The value is is rounded +to a multiple of 0.2 seconds. The default is 1 second, a value +suitable for polling across a LAN. +.TP +.B \-u +Direct ntpdate to use an unprivileged port for outgoing packets. +This is most useful when behind a firewall that blocks incoming +traffic to privileged ports, and you want to synchronise with +hosts beyond the firewall. Note that the -d option always uses +unprivileged ports. +.TP +.B \-v +Be verbose. This option will cause ntpdate's version +identification string to be logged. +.SH DIAGNOSTICS +\fBntpdate\fP's exit status is zero if it finds a server +and updates the clock, and nonzero otherwise. +.SH FILES +.TP +.I /etc/ntp.keys +\- encryption keys used by ntpdate. +.SH BUGS +The slew adjustment is actually 50% larger than the measured offset, +since this (it is argued) will tend to keep a badly drifting clock +more accurate. This is probably not a good idea and may cause a +troubling hunt for some values of the kernel variables tick and +tickadj. +.SH AUTHOR +David L. Mills (mills@udel.edu) +.br +This manpage converted from html to roff by +Fabrizio Polacco <fpolacco@debian.org> + |