[root@noc noc]# ntpd -v
ntpd: illegal option -- v
ntpd - NTP daemon program - Ver. 4.2.6p5
USAGE:  ntpd [ -<flag> [<val>] | --<name>[{=| }<val>] ]...
[root@noc noc]# ntpd -h
ntpd: illegal option -- h
ntpd - NTP daemon program - Ver. 4.2.6p5
USAGE:  ntpd [ -<flag> [<val>] | --<name>[{=| }<val>] ]...
[root@noc noc]# ntpd --help
ntpd - NTP daemon program - Ver. 4.2.6p5
USAGE:  ntpd [ -<flag> [<val>] | --<name>[{=| }<val>] ]...
  Flg Arg Option-Name    Description
   -4 no  ipv4           Force IPv4 DNS name resolution
                                - prohibits these options:
                                ipv6
   -6 no  ipv6           Force IPv6 DNS name resolution
                                - prohibits these options:
                                ipv4
   -a no  authreq        Require crypto authentication
                                - prohibits these options:
                                authnoreq
   -A no  authnoreq      Do not require crypto authentication
                                - prohibits these options:
                                authreq
   -b no  bcastsync      Allow us to sync to broadcast servers
   -c Str configfile     configuration file name
   -d no  debug-level    Increase output debug message level
                                - may appear multiple times
   -D Str set-debug-level Set the output debug message level
                                - may appear multiple times
   -f Str driftfile      frequency drift file name
   -g no  panicgate      Allow the first adjustment to be Big
                                - may appear multiple times
   -i Str jaildir        Jail directory
   -I Str interface      Listen on an interface name or address
                                - may appear multiple times
   -k Str keyfile        path to symmetric keys
   -l Str logfile        path to the log file
   -L no  novirtualips   Do not listen to virtual interfaces
   -m no  mlock          Lock memory
   -n no  nofork         Do not fork
   -N no  nice           Run at high priority
   -p Str pidfile        path to the PID file
                                - may appear up to 2 times
   -P Num priority       Process priority
   -q no  quit           Set the time and quit
   -r Str propagationdelay Broadcast/propagation delay
      Str saveconfigquit Save parsed configuration and quit
   -s Str statsdir       Statistics file location
   -t Str trustedkey     Trusted key number
                                - may appear multiple times
   -u Str user           Run as userid (or userid:groupid)
                                - may appear up to 2 times
   -U Num updateinterval interval in seconds between scans for new or dropped interfaces
      Str var            make ARG an ntp variable (RW)
                                - may appear multiple times
      Str dvar           make ARG an ntp variable (RW|DEF)
                                - may appear multiple times
   -x no  slew           Slew up to 600 seconds
   -! opt version        Output version information and exit
   -? no  help           Display extended usage information and exit
   -! no  more-help      Extended usage information passed thru pager

Options are specified by doubled hyphens and their name or by a single
hyphen and the flag character.

The following option preset mechanisms are supported:
 - examining environment variables named NTPD_*