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.TH NTPD 8 "2007-12-07" "Debian" "The Network Time Protocol (NTP) Distribution"
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ntpd \- Network Time Protocol (NTP) daemon
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[ -r \fIbroadcastdelay\fR ]
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[ -u \fIuser\fR[:\fIgroup\fR] ]
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[ -U \fIinterface_update_interval\fR ]
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The \fBntpd\fR program is an operating system daemon which sets and maintains the system time of day in synchronism with Internet standard time servers.
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It is a complete implementation of the Network Time Protocol (NTP) version 4, but also retains compatibility with version 3, as defined by RFC-1305, and version 1 and 2, as defined by RFC-1059 and RFC-1119, respectively.
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\fBntpd\fR does most computations in 64-bit floating-point arithmetic and does relatively clumsy 64-bit fixed-point operations only when necessary to preserve the ultimate precision, about 232 picoseconds.
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While the ultimate precision is not achievable with ordinary workstations and networks of today, it may be required with future gigahertz CPU clocks and gigabit LANs.
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The daemon can operate in any of several modes, including symmetric
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active/passive, client/server broadcast/multicast and manycast. A
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broadcast/multicast or manycast client can discover remote servers,
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compute server-client propagation delay correction factors and configure
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itself automatically. This makes it possible to deploy a fleet of
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workstations without specifying configuration details specific to the
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Ordinarily, \fBntpd\fR reads the \fIntp.conf\fR 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, obviating the need for a
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configuration file. This may be particularly appropriate when the
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local host is to be configured as a broadcast/multicast client or manycast
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client, with all peers being determined by listening to broadcasts at
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variables can be displayed and configuration
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options altered while the daemon is running using the
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starts it looks at the value of umask, and if it is zero
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will set the umask to 0222.
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Require cryptographic authentication for broadcast client, multicast client and symmetric passive associations.
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Do not require cryptographic authentication for broadcast client, multicast client and symmetric passive associations.
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This is almost never a good idea.
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Enable the client to synchronize to broadcast servers.
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\fB-c\fR \fIconffile\fR
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Specify the name and path of the configuration file, default \fI/etc/ntp.conf\fR.
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\fB-f\fR \fIdriftfile\fR
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Specify the name and path of the frequency file, default \fI/etc/ntp.drift\fR.
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This is the same operation as the driftfile \fIdriftfile\fR configuration command.
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Normally, \fBntpd\fR exits with a message to the system log if the offset exceeds the panic threshold, which is 1000 s by default.
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This option allows the time to be set to any value without restriction; however, this can happen only once.
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If the threshold is exceeded after that, \fBntpd\fR will exit with a message to the system log.
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This option can be used with the \fB-q\fR and \fB-x\fR options.
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\fB-i\fR \fIjaildir\fR
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Chroot the server to the directory \fIjaildir\fR.
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This option also implies that the server attempts to drop root privileges at startup (otherwise, chroot gives very little additional security).
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You may need to also specify a \fB-u\fR option.
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\fB-k\fR \fIkeyfile\fR
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Specify the name and path of the symmetric key file, default \fI/etc/ntp.keys\fR.
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This is the same operation as the keys \fIkeyfile\fR configuration command.
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\fB-l\fR \fIlogfile\fR
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Specify the name and path of the log file.
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The default is the system log file.
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This is the same operation as the logfile \fIlogfile\fR configuration command.
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Do not listen to virtual IPs.
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The default is to listen.
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To the extent permitted by the operating system, run the \fBntpd\fR at the highest priority.
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\fB-p\fR \fIpidfile\fR
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Specify the name and path of the file used to record the \fBntpd\fR process ID.
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This is the same operation as the pidfile \fIpidfile\fR configuration command.
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\fB-P\fR \fIpriority\fR
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To the extent permitted by the operating system, run the \fBntpd\fR at the specified priority.
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Exit the \fBntpd\fR just after the first time the clock is set.
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This behavior mimics that of the \fBntpdate\fR program, which is to be retired.
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The \fB-g\fR and \fB-x\fR options can be used with this option.
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Note: The kernel time discipline is disabled with this option.
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\fB-r\fR \fIbroadcastdelay\fR
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Specify the default propagation delay from the broadcast/multicast server to this client.
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This is necessary only if the delay cannot be computed automatically by the protocol.
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\fB-s\fR \fIstatsdir\fR
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Specify the directory path for files created by the statistics facility.
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This is the same operation as the statsdir \fIstatsdir\fR configuration command.
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Add a key number to the trusted key list.
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This option can occur more than once.
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\fB-u\fR \fIuser\fR[:\fIgroup\fR]
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Specify a user, and optionally a group, to switch to.
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\fB-U\fR \fIinterface_update_interval\fR
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Number of seconds to wait between interface list scans to pick up new and delete network interface.
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Set to 0 to disable dynamic interface list updating.
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The default is to scan every 5 minutes.
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\fB-v\fR \fIvariable\fR, \fB-V\fR \fIvariable\fR
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Add a system variable listed by default.
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Normally, 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.
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This option sets the threshold to 600 s, which is well within the accuracy window to set the clock manually.
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Note: 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.
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Thus, an adjustment as much as 600 s will take almost 14 days to complete.
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This option can be used with the \fB-g\fR and \fB-q\fR options.
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Note: The kernel time discipline is disabled with this option.
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default name of the configuration file
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default name of the drift file
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The complete documentation can be found at \fI/usr/share/doc/ntp\-doc/html/ntpd.html\fR in the package ntp\-doc.
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debian/man/ntpd.8
