ntpd - Network Time Protocol (NTP) daemon


   ntpd  [ -46aAbgLmnNqx ] [ -c conffile ] [ -f driftfile ] [ -i jaildir ]
   [ -k keyfile ] [ -l logfile ] [ -p pidfile ]  [  -P  priority  ]  [  -r
   broadcastdelay  ]  [  -s statsdir ] [ -t key ] [ -u user[:group] ] [ -U
   interface_update_interval ] [ -v variable ] [ -V variable ]


   The ntpd program is an operating system daemon which sets and maintains
   the  system  time  of  day  in  synchronism with Internet standard time
   servers.  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.    ntpd  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.  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.

   The daemon can operate in any of  several  modes,  including  symmetric
   active/passive,  client/server  broadcast/multicast  and  manycast.   A
   broadcast/multicast or manycast client  can  discover  remote  servers,
   compute   server-client   propagation   delay  correction  factors  and
   configure itself automatically.  This makes it  possible  to  deploy  a
   fleet of workstations without specifying configuration details specific
   to the local environment.

   Ordinarily, ntpd reads the ntp.conf configuration file at startup  time
   in  order to determine the synchronization sources and operating modes.
   It  is  also  possible  to  specify   a   working,   although   limited
   configuration  entirely  on  the command line, obviating the need for a
   configuration file.  This may  be  particularly  appropriate  when  the
   local  host  is  to  be  configured  as a broadcast/multicast client or
   manycast client, with  all  peers  being  determined  by  listening  to
   broadcasts at run time.

   Various  internal  ntpd  variables  can  be displayed and configuration
   options altered while the daemon is running using  the  ntpq  and  ntpd
   utility programs.

   When ntpd starts it looks at the value of umask, and if it is zero ntpd
   will set the umask to 0222.


   -a     Require  cryptographic  authentication  for  broadcast   client,
          multicast  client  and  symmetric passive associations.  This is
          the default.

   -A     Do  not  require  cryptographic  authentication  for   broadcast
          client,  multicast  client  and  symmetric passive associations.
          This is almost never a good idea.

   -b     Enable the client to synchronize to broadcast servers.

   -c conffile
          Specify the name and path of  the  configuration  file,  default

   -f driftfile
          Specify  the  name  and  path  of  the  frequency  file, default
          /etc/ntp.drift.  This is the same  operation  as  the  driftfile
          driftfile configuration command.

   -g     Normally,  ntpd  exits  with  a message to the system log if the
          offset exceeds the panic threshold, which is 1000 s by  default.
          This  option  allows  the  time  to  be set to any value without
          restriction;  however,  this  can  happen  only  once.   If  the
          threshold  is exceeded after that, ntpd will exit with a message
          to the system log.  This option can be used with the -q  and  -x

   -i jaildir
          Chroot  the  server  to the directory jaildir.  This option also
          implies that the server attempts  to  drop  root  privileges  at
          startup   (otherwise,   chroot   gives  very  little  additional
          security).  You may need to also specify a -u option.

   -I [address | interface name]
          Open the network address given, or all the addresses  associated
          with  the given interface name.  This option may appear multiple
          times.  This option also implies not  opening  other  addresses,
          except  wildcard  and  localhost.   This  option  is deprecated.
          Please consider using the configuration file interface  command,
          which is more versatile.

   -k keyfile
          Specify  the  name  and  path of the symmetric key file, default
          /etc/ntp.keys.  This is the same operation as the  keys  keyfile
          configuration command.

   -l logfile
          Specify  the  name and path of the log file.  The default is the
          system log file.  This is the  same  operation  as  the  logfile
          logfile configuration command.

   -L     Do not listen to virtual IPs.  The default is to listen.

   -n     Don't fork.

   -N     To the extent permitted by the operating system, run the ntpd at
          the highest priority.

   -p pidfile
          Specify the name and path of the file used to  record  the  ntpd
          process  ID.   This is the same operation as the pidfile pidfile
          configuration command.

   -P priority
          To the extent permitted by the operating system, run the ntpd at
          the specified priority.

   -q     Exit  the ntpd just after the first time the clock is set.  This
          behavior mimics that of the ntpdate  program,  which  is  to  be
          retired.   The  -g  and -x options can be used with this option.
          Note: The kernel time discipline is disabled with this option.

   -r broadcastdelay
          Specify    the    default    propagation    delay    from    the
          broadcast/multicast  server  to  this client.  This is necessary
          only if the  delay  cannot  be  computed  automatically  by  the

   -s statsdir
          Specify  the  directory path for files created by the statistics
          facility.  This is the same operation as the  statsdir  statsdir
          configuration command.

   -t key Add a key number to the trusted key list.  This option can occur
          more than once.

   -u user[:group]
          Specify a user, and optionally a group, to switch to.

   -U interface_update_interval
          Number of seconds to wait between interface list scans  to  pick
          up  new  and  delete  network  interface.   Set  to 0 to disable
          dynamic interface list updating.  The default is to scan every 5

   -v variable, -V variable
          Add a system variable listed by default.

   -x     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.   This  option  sets the threshold to 600 s, which is
          well within the accuracy  window  to  set  the  clock  manually.
          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.  Thus, an adjustment as much as 600 s will
          take almost 14 days to complete.  This option can be  used  with
          the  -g  and  -q  options.   Note: The kernel time discipline is
          disabled with this option.

   -4     Force IPv4 DNS name resolution.

   -6     Force IPv6 DNS name resolution.


          default name of the configuration file

          default name of the drift file


   ntp.conf(5), ntpdate(8)

   The     complete      documentation      can      be      found      at
   /usr/share/doc/ntp-doc/html/ntpd.html in the package ntp-doc.

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