Miscellaneous Commands and Options

This command specifies the complete path and name of the file used to record the frequency of the local clock oscillator; this is the same operation as the -f command line option. If the file exists, it is read at startup to set the initial frequency and then updated once per hour with the current frequency computed by the daemon. If the file name is specified, but the file itself does not exist, ntpd starts with an initial frequency of zero and creates the file when writing it for the first time. If this command is not given, the daemon will always start with an initial frequency of zero.

Provides a way to enable or disable various server options. Flags not mentioned are unaffected. Note that all of these flags can be controlled remotely using the ntpq(1) utility program.

This command allows additional configuration commands to be included from a separate file. Include files may be nested to a depth of five; upon reaching the end of any include file, command processing resumes in the previous configuration file. Relative pathnames are evaluated not with respect to the current working directory but with respect to the directory name of the last pushed file in the stack. This option is useful for sites that run ntpd(8) on multiple hosts, with (mostly) common options (e.g., a restriction list).

This command controls which network addresses ntpd opens, and whether the input is dropped without processing. The first parameter determines the action on addresses which match the second parameter. That parameter specifies a class of addresses, or a specific interface name, or an address. In the address case, prefixlen determines how many bits must match for this rule to apply. ignore prevents opening matching addresses, drop causes ntpd to open the address and drop all received packets without examination. Multiple interface commands can be used. The last rule which matches a particular address determines the action for it. interface commands are disabled if any of the -I, --interface,-L, or --novirtualips command-line options are used. If none of those options are used, and no interface actions are specified in the configuration file, all available network addresses are opened. The nic command is an alias for interface.

This command loads the NIST leap seconds file and initializes the leapsecond values for the next leap second time, expiration time and TAI offset. The file can be obtained using ntpleapfetch.

This experimental option is only available if ntpd was built with the --enable-leap-smear option, It specifies the interval over which a leap second correction will be applied. Recommended values for this option are between 7200 (2 hours) and 86400 (24 hours). DO NOT USE THIS OPTION ON PUBLIC-ACCESS SERVERS! See http://bugs.ntp.org/2855 for more information.

This command controls the amount and type of output written to the system syslog(3) facility or the alternate log file. By default, all output is turned on. All configkeyword keywords can be prefixed with ‘=’, ‘’ and ‘-’, where ‘=’ sets the syslog(3) priority mask, ‘’ adds and ‘-’ removes messages. syslog(3) messages can be controlled in four classes (clock,peer,sys and sync). Within these classes four types of messages can be controlled: informational messages (info), event messages (events), statistics messages (statistics) and status messages (status).

logconfig =syncstatus +sysevents

logconfig =syncall +clockall

This command specifies the location of an alternate log file to be used instead of the default system syslog(3) facility; this is the same operation as the -l command line option.

Controls size limits of the monitoring facility Most Recently Used (MRU) list of client addresses, which is also used by the rate control facility.

Specify the threshold in seconds to write the frequency file, with a default of 1e-7 (0.1 PPM). The frequency file is inspected each hour. If the difference between the current frequency and the last value written exceeds the threshold, the file is written, and the threshold becomes the new threshold value. If the threshold is not exceeded, it is reduced by half; this is intended to reduce the frequency of unnecessary file writes for embedded systems with nonvolatile memory.

This command is used in conjunction with the ACTS modem driver (type modem) or the JJY driver (type jjy). For ACTS, the arguments consist of a maximum of 10 telephone numbers used to dial USNO, NIST or European time services. For the jjy driver in modes 100-180, the argument is one telephone number used to dial the telephone JJY service. The Hayes command ATDT is normally prepended to the number, which can contain other modem control codes as well.

Reset one or more groups of counters maintained by ntpd and exposed by ntpq.

This command adds a system variable. These variables can be used to distribute additional information such as the access policy. If the variable of the form name=value is followed by the default keyword, the variable will be listed as part of the default system variables (ntpq(1) rv command). These additional variables serve informational purposes only. They are not related to the protocol other that they can be listed. The known protocol variables will always override any variables defined via the setvar mechanism. There are three special variables that contain the names of all variable of the same group. The sys_var_list holds the names of all system variables. The peer_var_list holds the names of all peer variables and the clock_var_list holds the names of the reference clock variables.

This command can be used to alter several system variables in very exceptional circumstances. It should occur in the configuration file before any other configuration options. The default values of these variables have been carefully optimized for a wide range of network speeds and reliability expectations. In general, they interact in intricate ways that are hard to predict, and some combinations can result in some very nasty behavior. Very rarely is it necessary to change the default values; but, some folks cannot resist twisting the knobs anyway, and this command is for them. Emphasis added: twisters are on their own and can expect no help from the support group.

This command alters certain system variables used by the clock selection and clustering algorithms. The default values of these variables have been carefully optimized for a wide range of network speeds and reliability expectations. Very rarely is it necessary to change the default values; but, some folks can’t resist twisting the knobs. It can be used to select the quality and quantity of peers used to synchronize the system clock and is most useful in dynamic server discovery schemes. The options are as follows:

This command specifies the Differentiated Services Code Point (DSCP) value that is used in sent NTP packets. The default value is 46 for Expedited Forwarding (EF).