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NTP Information Disclosure Vulnerability
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ntpdate(1M) ntpdate(1M) NAME
ntpdate - set the date and time via NTP SYNOPSIS
[ ] [ key# ] [ authdelay ] [ keyfile ] [ version ] [ samples ] [ timeout ] server[ ... ] DESCRIPTION
sets the local date and time by polling those Network Time Protocol (NTP) server(s) given as the 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 depends on the number of servers, the number of polls each time it is run, and the interval between the runs. 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 It is also possible to run from a cron script. However, it is important to note that 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 does not discipline the host clock frequency as does the accuracy using is limited. Time adjustments are made by in one of two ways. If determines the clock is in error more than 0.5 seconds, it will simply step the time by calling the (see clocks(2)) system routine. If the error is less than 0.5 seconds, it will slew the time by calling the (see adjtime(2)) system routine. The latter technique is less disruptive and more accurate when the error is small, and works quite well when is run by (see cron(1M)) every hour or two. will decline to set the date if an NTP server daemon (e.g., is running on the same host. When running on a regular basis from as an alter- native to running a daemon, doing so once every hour or two will result in precise enough timekeeping to avoid stepping the clock. Command Line Options supports the following options: Enable the authentication function and specify the key identifier to be used for authentication. The keys and key identifiers must match in both the client and server key files. The default is to disable the authentication function. Force the time to always be slewed using the system call, even if the measured offset is greater than The default is to step the time using the system call if the offset is greater than Note that, if the offset is much greater than it can take a long time (hours) to slew the clock to the cor- rect value. During this time the host should not be used to synchronize clients. Force the time to be stepped using the system call, rather than slewed (default) using the system call. This option should be used when called from a startup file at boot time. Enable the debugging mode, in which will go through all the steps, but not adjust the local clock. Information useful for general debugging will also be printed. Specify the processing delay to perform an authentication function as the value authdelay, in seconds and fraction (see xntpd(1M) for details). This number is usually small enough to be negligi- ble for most purposes, though specifying a value may improve timekeeping on very slow CPU's. Specify the path for the authentication key file as the string keyfile. The default is This file should be in the format described in Specify the NTP version for outgoing packets as the integer version, which can be 1 or 2. The default is 3. This allows to be used with older NTP versions. 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. Prints the offset measurement, stratum of the server(s) and delay measurement without adjusting the local clock. This is similar to option which gives a more detailed debugging information. Divert logging output from the standard output (default) to the system (see syslog(3C)) facility. This is designed primarily for convenience of scripts. Specify the maximum waiting time for a server response as the value timeout, in seconds and fraction. The value is rounded to a multiple of 0.2 seconds. The default is 1 second, a value suit- able for polling across a LAN. Direct 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 option always uses unprivi- leged ports. Prints the version number and the offset measurement information. AUTHOR
was developed by Dennis Ferguson at the University of Toronto. FILES
Contains the encryption keys used by SEE ALSO
adjtime(2), clocks(2), cron(1M), syslog(3C), ntpq(1M), xntpd(1M), xntpdc(1M). DARPA Internet Request For Comments RFC1035 Assigned Numbers. ntpdate(1M)
