252 lines
6.6 KiB
Groff
252 lines
6.6 KiB
Groff
.\"
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.\" $FreeBSD$
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.\"
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.Dd January 10, 2000
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.Dt NTPD 8
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.Os
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.Sh NAME
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.Nm ntpd
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.Nd Network Time Protocol (NTP) daemon
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.Sh SYNOPSIS
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.Nm ntpd
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.Op Fl aAbdgmx
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.Op Fl c Ar conffile
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.Op Fl f Ar driftfile
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.Op Fl k Ar keyfile
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.Op Fl l Ar logfile
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.Op Fl p Ar pidfile
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.Op Fl r Ar broadcastdelay
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.Op Fl s Ar statsdir
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.Op Fl t Ar trustedkey
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.Op Fl v Ar variable
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.Op Fl V Ar variable
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.Sh DESCRIPTION
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.Nm
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is an operating system daemon
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which sets and maintains the system time-of-day
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in synchronism with Internet standard time servers.
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.Nm
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is a complete implementation of the Network Time Protocol (NTP)
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version 4,
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but also retains compatibility with version 3,
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as defined by RFC 1305,
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and version 1 and 2,
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as defined by RFC 1059 and RFC 1119,
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respectively.
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.Nm
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does most computations in 64-bit floating point arithmetic
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and does relatively clumsy 64-bit fixed point operations
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only when necessary to preserve the ultimate precision,
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about 232 picoseconds.
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While the ultimate precision is not achievable
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with ordinary workstations and networks of today,
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it may be required with future nanosecond CPU clocks and gigabit LANs.
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.Pp
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The daemon can operate in any of several modes,
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including symmetric active/passive,
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client/server broadcast/multicast and manycast.
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A broadcast/multicast or manycast client can discover remote servers,
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compute server-client propagation delay correction factors
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and configure itself automatically.
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This makes it possible to deploy a fleet of workstations
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without specifying configuration details
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specific to the local environment.
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.Pp
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Ordinarily,
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.Nm
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reads the
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.Xr ntp.conf 5
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configuration file at startup time
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in order to determine the synchronization sources and operating modes.
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It is also possible to specify a working, although limited,
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configuration entirely on the command line,
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obviating the need for a configuration file.
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This may be particularly appropriate
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when the local host is to be configured
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as a broadcast/multicast client or manycast client,
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with all peers being determined
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by listening to broadcasts at run time.
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.Pp
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If NetInfo support is built into
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.Nm Ns ,
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then
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.Nm
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will attempt to read its configuration from the NetInfo
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if the default configuration file cannot be read
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and no file is specified by the
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.Fl c
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option.
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.Pp
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Various
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internal
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.Nm
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variables can be displayed and configuration options altered
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while the daemon is running
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through use of the
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.Xr ntpq 8
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and
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.Xr ntpdc 8
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programs.
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.Pp
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When
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.Nm
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starts it looks at the value of
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.Xr umask 2
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and if it is zero,
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.Nm
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will set it to 022.
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.Pp
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The following command line options are available:
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.Bl -tag -width indent
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.It Fl a
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Enable authentication mode (default).
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.It Fl A
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Disable authentication mode.
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.It Fl b
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Synchronize using NTP broadcast messages.
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.It Fl c Ar conffile
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Specify the name and path of the configuration file.
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.It Fl d
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Specify debugging mode.
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This flag may occur multiple times,
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with each occurrence indicating greater detail of display.
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.It Fl D Ar level
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Specify debugging level directly.
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.It Fl f Ar driftfile
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Specify the name and path of the drift file.
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.It Fl g
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Normally, the daemon exits
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if the offset exceeds a 1000 s sanity limit.
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This option overrides this limit
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and allows the time to be set to any value without restriction;
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however, this can happen only once.
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After that,
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the daemon will exit if the limit is exceeded.
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.It Fl k Ar keyfile
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Specify the name and path of the file
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containing the NTP authentication keys.
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.It Fl l Ar logfile
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Specify the name and path of the log file.
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The default is the system log facility.
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.It Fl m
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Synchronize using NTP multicast messages
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on the IP multicast group address 224.0.1.1
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(requires multicast kernel).
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.It Fl p Ar pidfile
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Specify the name and path to record the daemon's process ID.
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.It Fl P
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Override the priority limit set by the operating system.
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Not recommended for sissies.
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.It Fl r Ar broadcastdelay
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Specify the default propagation delay
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between the broadcast/multicast server and this computer.
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This is necessary
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only if the delay cannot be computed automatically by the protocol.
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.It Fl s Ar statsdir
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Specify the directory path for files created by the statistics
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facility.
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.It Fl t Ar key
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Add a key number to the trusted key list.
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.It Fl v Ar variable
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.It Fl V Ar variable
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Add a system variable listed by default.
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.It Fl x
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Ordinarily, if the time is to be adjusted more than 128 ms,
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it is stepped, not gradually slewed.
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This option forces the time to be slewed in all cases.
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Note: since the slew rate is limited to 0.5 ms/s,
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each second of adjustment requires an amortization interval of 2000 s.
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Thus, an adjustment of many seconds can take hours or days to amortize.
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.El
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.Ss Variables
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Most variables used by the NTP protocol
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can be examined with
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.Xr ntpdc 8
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(mode 7 messages) and
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.Xr ntpq 8
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(mode 6 messages).
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Currently, very few variables can be modified via mode 6 messages.
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These variables are either created with the
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.Ic setvar
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directive
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(described in the
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.Qq Miscellaneous Options
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section of the
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.Xr ntp.conf 5
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page)
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or the leap warning bits.
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The leap warning bits can be set in the
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.Va leapwarning
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variable up to one month ahead.
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Both the
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.Va leapwarning
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and
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.Va leapindication
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variables have a slightly different encoding
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than the usual leap bits interpretation:
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.Pp
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.Bl -tag -width indent -compact
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.It 00
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The daemon passes the leap bits of its synchronization source
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(usual mode of operation).
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.It 01
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.It 10
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A leap second is added/deleted (operator forced leap second).
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.It 11
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Leap information from the synchronizations source is ignored
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(thus
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.Dv LEAP_NOWARNING
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is passed on).
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.El
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.Sh FILES
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.Bl -tag -width /etc/ntp.drift -compact
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.It Pa /etc/ntp.conf
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the default name of the configuration file
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.It Pa /etc/ntp.drift
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the default name of the drift file
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.It Pa /etc/ntp.keys
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the default name of the key file
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.El
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.Sh SEE ALSO
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.Xr ntp.conf 5 ,
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.Xr ntpdate 8 ,
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.Xr ntpdc 8 ,
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.Xr ntpq 8
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.Pp
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In addition to the manual pages provided,
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comprehensive documentation is available on the world wide web
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at
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.Li http://www.ntp.org/ .
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A snapshot of this documentation is available in HTML format in
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.Pa /usr/share/doc/ntp .
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.Rs
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.%A David L. Mills
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.%T Network Time Protocol (Version 1)
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.%O RFC1059
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.Re
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.Rs
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.%A David L. Mills
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.%T Network Time Protocol (Version 2)
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.%O RFC1119
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.Re
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.Rs
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.%A David L. Mills
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.%T Network Time Protocol (Version 3)
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.%O RFC1305
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.Re
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.Sh HISTORY
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Written by
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.An Dennis Ferguson
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at the University of Toronto.
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Text amended by
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.An David Mills
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at the University of Delaware.
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.Sh BUGS
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.Nm
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has gotten rather fat.
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While not huge, it has gotten larger than might
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be desireable for an elevated-priority daemon running on a workstation,
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particularly since many of the fancy features which consume the space
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were designed more with a busy primary server, rather than a high
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stratum workstation, in mind.
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