Provided by: linuxptp_3.1.1-3_amd64 bug

NAME

       phc2sys - synchronize two or more clocks

SYNOPSIS

       phc2sys -a [ -r ] [ -r ] [ -f config-file ] [ options ] [ long-options ]
       phc2sys  [  -f config-file ] [ -d pps-device ] [ -s device ] [ -c device ] [ -O offset ] [
       -w ] [ options ] [ long-options ] ...

DESCRIPTION

       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.

OPTIONS

       -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.

       -f config
              Read configuration from the specified  file.  No  configuration  file  is  read  by
              default.

       -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
              option. This option does not support bonded interface (e.g. bond0, team0). If ptp4l
              has a port on an active-backup bond or team interface, the -a option can be used to
              track the active interface.

       -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
              option.

       -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  changing  the  clock  frequency. 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
              /var/run/ptp4l.

       -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).

       -t message-tag
              Specify  the  tag  which is added to all messages printed to the standard output or
              system log. The default is an empty string.

       -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.

LONG OPTIONS

       Each and every configuration file option (see below  in  section  FILE OPTIONS)  may  also
       appear as a "long" style command line argument.  For example, the transportSpecific option
       may be set using either of these two forms:

              --transportSpecific 1   --transportSpecific=1

       Option values given on the command line override values  in  the  global  section  of  the
       configuration file (which, in turn overrides default values).

CONFIGURATION FILE

       The  configuration  file  is  divided  into  sections.  Each  section  starts  with a line
       containing its name enclosed in brackets and it follows with settings.   Each  setting  is
       placed  on  a separate line, it contains the name of the option and the value separated by
       whitespace characters. Empty lines and lines starting with # are ignored.

       The global section (indicated as [global]) sets the program options. This is the only used
       option.

FILE OPTIONS

       domainNumber
              Specify the domain number used by phc2sys. The default is 0. Same as option -n (see
              above).

       kernel_leap
              When a leap second is announced, let the kernel apply  it  by  stepping  the  clock
              instead  of  correcting  the  one-second offset with servo, which would correct the
              one-second offset slowly by changing the clock frequency (unless the step_threshold
              option is set to correct such offset by stepping). Relevant only with software time
              stamping. The default is 1 (enabled). Same as option -x (see above).

              The maximum logging level of messages which should be printed.  The  default  is  6
              (LOG_INFO). Same as option -l (see above).

       logging_level
              The  maximum  logging  level of messages which should be printed.  The default is 6
              (LOG_INFO). Same as option -l (see above).

       message_tag
              The tag which is added to all messages printed to the  standard  output  or  system
              log.  The default is an empty string (which cannot be set in the configuration file
              as the option requires an argument).  Same as option -t (see above).

       sanity_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%).  Same as option -L (see above).

       clock_servo
              The servo which is used to synchronize the local clock. Valid values are "pi" for a
              PI  controller,  "linreg"  for  an  adaptive  controller  using  linear regression,
              "ntpshm" for the NTP SHM reference clock to allow another  process  to  synchronize
              the  local  clock (the SHM segment number is set to the domain number), and "nullf"
              for a servo that always dials frequency offset zero (for use in SyncE  nodes).  The
              default is "pi."  Same as option -E (see above).

       transportSpecific
              The transport specific field. Must be in the range 0 to 255.  The default is 0.

       use_syslog
              Print  messages to the system log if enabled.  The default is 1 (enabled).  Related
              to option -q (see above).

       verbose
              Print messages to the standard output if enabled.  The  default  is  0  (disabled).
              Related to option -m (see above).

       pi_proportional_const
              Specifies  the  proportional constant of the PI controller.  Same as option -P (see
              above).

       pi_integral_const
              Specifies the integral constant of the PI  controller.   Same  as  option  -I  (see
              above).

       step_threshold
              Specifies  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.  Same as option
              -S (see above).

       first_step_threshold
              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).   Same
              as option -F (see above).

       ntpshm_segment
              The  number  of  the  SHM segment used by ntpshm servo.  The default is 0.  Same as
              option -M (see above).

       uds_address
              Specifies  the  address  of  the  server's  UNIX  domain  socket.  The  default  is
              /var/run/ptp4 Same as option -z (see above).

TIME SCALE USAGE

       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.

EXAMPLES

       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

       Same as above, in an IEEE 802.1AS domain.

              phc2sys -a -rr --transportSpecific=1

       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
       ptp4l.

              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

WARNING

       Be cautious when the same configuration file is used for both ptp4l and phc2sys.  Keep  in
       mind,  that  values specified in the configuration file take precedence over their default
       values. If a certain option, which is common to ptp4l and phc2sys, is specified to a  non-
       default  value  in  the  configuration file (p.e., for ptp4l), then this non-default value
       applies also for phc2sys. This might be not what is expected.

       It is recommended to use seperate configuration files for ptp4l and phc2sys  in  order  to
       avoid any unexpected behavior.

SEE ALSO

       ptp4l(8)