NAME

       ntpdig - standard Simple Network Time Protocol client program

SYNOPSIS

       ntpdig
           [--help | -?] [-4 | -6] [-a keynum] [-p samples]
           [-c] [-d] [-D debug-level] [-g delay] [-j] [-k keyfile]
           [-l logfile] [-M steplimit] [-S] [-s]
           [--wait] [--no-wait] [--version] [address...]+

DESCRIPTION

       ntpdig can be used as an SNTP client to query an NTP or SNTP server and either display the time or set
       the local system’s time (given suitable privilege). It can be run as an interactive command or from a
       cron job. NTP (the Network Time Protocol) and SNTP (the Simple Network Time Protocol) are defined and
       described by RFC 5905.

       The default is to write the estimated correct local date and time (i.e. not UTC) to the standard output
       in a format like:

           2015-10-14 13:46:04.534916 (+0500) -0.000007 +/- 0.084075 localhost 127.0.0.1 s2 no-leap

       where the (+0500) means that to get to UTC from the reported local time one must add 5 hours and 0
       minutes, the -0.000007 indicates the local clock is 0.000007 seconds ahead of correct time (so 0.000007
       seconds must be subtracted from the local clock to get it to be correct). Note that the number of
       decimals printed for this value will change based on the reported precision of the server. +/- 0.084075
       is the reported synchronization distance (in seconds), which represents the maximum error due to all
       causes. If the server does not report valid data needed to calculate the synchronization distance, this
       will be reported as +/- ?.

       If the host is different from the IP, both will be displayed. Otherwise, only the IP is displayed.
       Finally, the stratum of the host is reported and the leap indicator is decoded and displayed.

       With the -j (JSON) option, the output format becomes a self-describing JSON record:

           {"time":"2015-10-14T13:46:04.534916+0500",
                    "offset":-0.000007,"precision":"0.084075",
                    "host":"localhost",ip:"127.0.0.1",
                    "stratum":2,"leap":"noleap","adjusted":false}

       In the JSON format, time is in ISO 8601 format; precision is the synch distance, with an unknown synch
       distance being reported as 0. Host and IP are always emitted even if duplicate. The "adjusted" boolean
       reports whether ntpdig determined it should have slewed or stepped the time. This may be shown as true
       even if time was not actually adjusted due to lack of clock-setting privileges.

OPTIONS

       -h, --help
           Displays usage information and exits.

       -4, --ipv4
           Force IPv4 DNS name resolution. This option must not appear in combination with any of the following
           options: ipv6.

           Force DNS resolution of the following host names on the command line to the IPv4 namespace.

       -6, --ipv6
           Force IPv6 DNS name resolution. This option must not appear in combination with any of the following
           options: ipv4.

           Force DNS resolution of the following host names on the command line to the IPv6 namespace.

       -a auth-keynumber, --authentication=auth-keynumber
             Enable authentication with the key auth-keynumber. This option takes an integer number as its
           argument.

           Enable authentication using the key specified in this option’s argument. The argument of this option
           is the keyid, a number specified in the keyfile as this key’s identifier. See the keyfile option (-k)
           for more details.

       -c host-name, --concurrent=host-name
           Concurrently query all IPs returned for host-name. This option may appear an unlimited number of
           times.

           Requests from an NTP "client" to a "server" should never be sent more rapidly than one every 2
           seconds. By default, any IPs returned as part of a DNS lookup are assumed to be for a single instance
           of ntpd, and therefore ntpdig will send queries to these IPs one after another, with a 2-second gap
           in between each query.

           The -c or --concurrent flag says that any IPs returned for the DNS lookup of the supplied host-name
           are on different machines, so we can send concurrent queries. This is appropriate when using a server
           pool.

       -d, --debug-level
           Increase debug verbosity level. This option may appear an unlimited number of times.

       -D number, --set-debug-level=number
           Set the debug verbosity level. This option may appear an unlimited number of times. This option takes
           an integer number as its argument.

       -g milliseconds, --gap=milliseconds
           The gap (in milliseconds) between time requests. This option takes an integer number as its argument.
           The default milliseconds for this option is 50.

           Separate the queries we send out by the specified number of milliseconds. A larger delay reduces the
           query load on the time sources, at the cost of increasing the time to receive a valid response if the
           first source attempted is slow or unreachable.

       -j
           Output to stdout in JSON, suppressing syslog messages.

       -k file-name, --keyfile=file-name
           Look in this file for the key specified with -a.

           This option specifies the keyfile. ntpdig will search for the key specified with -a keyno in this
           file. See ntp.keys(5) for more information.

       -l file-name, --logfile=file-name
           Log to specified logfile.

           This option causes the client to write log messages to the specified logfile.

       -M number, --steplimit=number
           Adjustments less than steplimit milliseconds will be slewed. This option takes an integer number as
           its argument. The value of number is constrained to being greater than or equal to 0,

           If the time adjustment is less than steplimit milliseconds, slew the amount using adjtime(2).
           Otherwise, step the correction using clock_settime() or local equivalent. The default value is 0,
           which means all adjustments will be stepped. This is a feature, as different situations demand
           different values.

       -p, --samples
           The number of samples to take (default 1). The best one (chosen by, among other criteria, sync
           distance) is selected for display or use.

       -S, --step
           By default, ntpdig displays the clock offset but does not attempt to correct it. This option enables
           offset correction by stepping, that is, directly setting the clock to the corrected time. This
           typically requires ntpdig be invoked as the superuser ("root").

       -s, --slew
           By default, ntpdig displays the clock offset but does not attempt to correct it. This option enables
           offset correction by slewing using adjtime(), which changes the rate of the clock for a period long
           enough to accomplish the required offset (phase) correction. This typically requires ntpdig be
           invoked as the superuser ("root").

       -t seconds, --timeout=seconds
           The number of seconds to wait for responses. This option takes an integer number as its argument. The
           default seconds for this option is: 5.

           When waiting for a reply, ntpdig will wait the number of seconds specified before giving up. The
           default should be more than enough for a unicast response. If ntpdig is only waiting for a broadcast
           response a longer timeout is likely needed.

       --wait, --no-wait
           Wait for pending replies (if not setting the time). The no-wait form will disable the option. This
           option is enabled by default.

           If we are not setting the time, wait for all pending responses.

       --version
           Output version of program and exit.

USAGE

       ntpdig ntpserver.somewhere
           is the simplest use of this program and can be run as an unprivileged command to check the current
           time and error in the local clock.

       ntpdig -S -s -M 128 ntpserver.somewhere
           With suitable privilege, run as a command or from a cron(8) job, ntpdig -Ss -M 128
           ntpserver.somewhere will request the time from the server, and if that server reports that it is
           synchronized then if the offset adjustment is less than 128 milliseconds the correction will be
           slewed, and if the correction is more than 128 milliseconds the correction will be stepped.

       ntpdig -S ntpserver.somewhere
           With suitable privilege, run as a command or from a cron(8) job, ntpdig -S ntpserver.somewhere will
           set (step) the local clock from a synchronized specified server, like the ntpdate utility from older
           NTP implementations.

COMPATIBILITY

       Not all options of the NTP classic sntp(1) utility have been retained; don’t expect -b, -K, -o, -r, -w,
       or -W to work. These have either been removed for security reasons or discarded as unnecessary in a
       modern environment.

       This version does not log to syslog. Pipe standard output and standard error to logger(1) if you want
       this behavior.

       The synchronization-distance formula used in this version is slightly different from that found in
       sntp(1), tracking the newer formula used in ntpd(8). Expect offset computations to match but
       synch-distances not to.

AUTHORS

       Johannes Maximilian Kuehn, Harlan Stenn, Dave Hart.

EXIT STATUS

       One of the following exit values will be returned:

       0 (EXIT_SUCCESS)
           Successful program execution.

       1 (EXIT_FAILURE)
           The operation failed or the command syntax was not valid.