Provided by: linuxptp_1.6-1_amd64 bug


       phc2sys - synchronize two or more clocks


       phc2sys -a [ -r ] [ -r ] [ options ]
       phc2sys [ -d pps-device ] [ -s device ] [ -c device ] [ -O offset ] [ -w ] [ options ]


       phc2sys is a program which synchronizes two or more clocks in the system. Typically, it is
       used to synchronize the system clock to a  PTP  hardware  clock  (PHC),  which  itself  is
       synchronized by the ptp4l(8) program.

       With  the  -a  option, the clocks to synchronize are fetched from the running ptp4l daemon
       and the direction of synchronization automatically follows changes of the PTP port states.

       Manual  configuration  is  also   possible.   When   using   manual   configuration,   two
       synchronization  modes are supported, one uses a pulse per second (PPS) signal provided by
       the source clock and the other mode reads time from the source clock directly. Some clocks
       can  be  used  in  both modes, the mode which will synchronize the slave clock with better
       accuracy depends on hardware and driver implementation.


       -a     Read the clocks to synchronize from running ptp4l and follow changes  in  the  port
              states,  adjusting  the  synchronization  direction automatically. The system clock
              (CLOCK_REALTIME) is not synchronized, unless the -r option is also specified.

       -r     Only valid together with the -a option. Instructs phc2sys to also  synchronize  the
              system  clock (CLOCK_REALTIME). By default, the system clock is not considered as a
              possible time source. If you want the system clock to be eligible to become a  time
              source, specify the -r option twice.

       -d pps-device
              Specify  the  PPS device of the master clock (e.g. /dev/pps0). With this option the
              PPS synchronization mode is used instead of the direct mode. As the PPS signal does
              not  specify  time  and  only  marks  start  of a second, the slave clock should be
              already close to the correct time before phc2sys is started or the -s option should
              be  used  too.  With  the  -s  option the PPS signal of the master clock is enabled
              automatically, otherwise it has to be enabled before phc2sys is  started  (e.g.  by
              running  echo  1  >  /sys/class/ptp/ptp0/pps_enable).  This option can be used only
              with the system clock as the slave clock. Not compatible with the -a option.

       -s device
              Specify the master clock by device (e.g. /dev/ptp0) or interface (e.g. eth0) or  by
              name  (e.g. CLOCK_REALTIME for the system clock). When this option is used together
              with the -d option, the master clock is used only to correct the  offset  by  whole
              number of seconds, which cannot be fixed with PPS alone. Not compatible with the -a

       -i interface
              Performs the exact same  function  as  -s  for  compatibility  reasons.  Previously
              enabled specifying master clock by network interface. However, this can now be done
              using -s and this option is no longer necessary. As such it  has  been  deprecated,
              and should no longer be used.

       -c device
              Specify  the  slave clock by device (e.g. /dev/ptp1) or interface (e.g. eth1) or by
              name. The default is CLOCK_REALTIME (the system clock). Not compatible with the  -a

       -E servo
              Specify  which clock servo should be used. Valid values are pi for a PI controller,
              linreg for an adaptive controller using linear regression, and ntpshm for  the  NTP
              SHM  reference  clock to allow another process to synchronize the local clock.  The
              default is pi.

       -P kp  Specify the proportional constant of the PI controller. The default is 0.7.

       -I ki  Specify the integral constant of the PI controller. The default is 0.3.

       -S step
              Specify the step threshold of the servo. It is the maximum offset  that  the  servo
              corrects  by  changing the clock frequency instead of stepping the clock. The clock
              is stepped on start regardless of the option  if  the  offset  is  larger  than  20
              microseconds  (unless  the -F option is used). It's specified in seconds. The value
              of 0.0 disables stepping after the start. The default is 0.0.

       -F step
              Specify the step threshold applied only on the first  update.  It  is  the  maximum
              offset  that  is corrected by adjusting clock. It's specified in seconds. The value
              of 0.0 disables stepping on start.  The default is 0.00002 (20 microseconds).

       -R update-rate
              Specify the slave clock update rate when  running  in  the  direct  synchronization
              mode. The default is 1 per second.

       -N phc-num
              Specify  the  number  of master clock readings per one slave clock update. Only the
              fastest reading is used to update the slave clock, this is useful to  minimize  the
              error caused by random delays in scheduling and bus utilization.  The default is 5.

       -O offset
              Specify  the  offset  between the slave and master times in seconds. Not compatible
              with the -a option.  See TIME SCALE USAGE below.

       -L freq-limit
              The maximum allowed frequency offset  between  uncorrected  clock  and  the  system
              monotonic  clock  in parts per billion (ppb). This is used as a sanity check of the
              synchronized clock. When a larger offset is measured, a  warning  message  will  be
              printed  and  the servo will be reset. When set to 0, the sanity check is disabled.
              The default is 200000000 (20%).

       -M segment
              The number of the SHM segment used by ntpshm servo.  The default is 0.

       -u summary-updates
              Specify the number of clock updates included in summary statistics. The  statistics
              include  offset  root  mean square (RMS), maximum absolute offset, frequency offset
              mean and standard deviation, and mean of the delay in clock readings  and  standard
              deviation.  The  units  are  nanoseconds  and parts per billion (ppb). If zero, the
              individual samples are printed instead of the statistics. The messages are  printed
              at the LOG_INFO level.  The default is 0 (disabled).

       -w     Wait  until  ptp4l  is  in a synchronized state. If the -O option is not used, also
              keep the offset between the  slave  and  master  times  updated  according  to  the
              currentUtcOffset  value  obtained  from  ptp4l  and  the  direction  of  the  clock
              synchronization. Not compatible with the -a option.

       -n domain-number
              Specify the domain number used by ptp4l. The default is 0.

       -x     When a leap second is announced, don't apply it  in  the  kernel  by  stepping  the
              clock, but let the servo correct the one-second offset slowly by changing the clock
              frequency (unless the -S option is used).

       -z uds-address
              Specifies the  address  of  the  server's  UNIX  domain  socket.   The  default  is

       -l print-level
              Set  the  maximum  syslog  level of messages which should be printed or sent to the
              system logger. The default is 6 (LOG_INFO).

       -m     Print messages to the standard output.

       -q     Don't send messages to the system logger.

       -h     Display a help message.

       -v     Prints the software version and exits.


       Ptp4l uses either PTP time scale or UTC (Coordinated Universal Time) time scale.  PTP time
       scale  is  continuous  and  shifted against UTC by a few tens of seconds as PTP time scale
       does not apply leap seconds.

       In hardware time stamping mode, ptp4l announces use of PTP time scale and PHC is used  for
       the  stamps.   That  means  PHC must follow PTP time scale while system clock follows UTC.
       Time offset between these two is maintained by phc2sys.

       Phc2sys acquires the offset value either by reading it from ptp4l when  -a  or  -w  is  in
       effect  or  from command line when -O is supplied.  Failure to maintain the correct offset
       can result in local system clock being off some seconds to domain master system clock when
       in  slave  mode,  or  incorect  PTP  time announced to the network in case the host is the
       domain master.


       Synchronize time automatically according to  the  current  ptp4l  state,  synchronize  the
       system clock to the remote master.

              phc2sys -a -r

       Same as above, but when the host becomes the domain master, synchronize time in the domain
       to its system clock.

              phc2sys -a -rr

       The host is a domain master, PTP clock is synchronized to system clock and the time offset
       is  obtained  from  ptp4l.   Phc2sys waits for ptp4l to get at least one port in master or
       slave mode before starting the synchronization.

              phc2sys -c /dev/ptp0 -s CLOCK_REALTIME -w

       Same as above, time offset is provided on command line  and  phc2sys  does  not  wait  for

              phc2sys -c /dev/ptp0 -s CLOCK_REALTIME -O 35

       The  host is in slave mode, system clock is synchronized from PTP clock, phc2sys waits for
       ptp4l and the offset is set automatically.

              phc2sys -s /dev/ptp0 -w

       Same as above, PTP clock id is read from the network interface, the offset is provided  on
       command line phc2sys does not wait.

              phc2sys -s eth0 -O -35