.TH TIMEMASTER 8 "October 2014" "linuxptp"

.SH NAME

timemaster - run NTP with PTP as reference clocks

.SH SYNOPSIS

.B timemaster

[

.B \-nmqv

] [

.BI \-l " print-level"

]

.BI \-f " file"

.SH DESCRIPTION

\fBtimemaster\fR is a program that uses \fBptp4l\fR and \fBphc2sys\fR in

combination with \fBchronyd\fR or \fBntpd\fR to synchronize the system clock to

NTP and PTP time sources. The PTP time is provided by \fBphc2sys\fR and

\fBptp4l\fR via SHM reference clocks to \fBchronyd\fR/\fBntpd\fR, which

can compare all time sources and use the best sources to synchronize the system

clock.

On start, \fBtimemaster\fR reads a configuration file that specifies the NTP

and PTP time sources, checks which network interfaces have and share a PTP

hardware clock (PHC), generates configuration files for \fBptp4l\fR and

\fBchronyd\fR/\fBntpd\fR, and start the \fBptp4l\fR, \fBphc2sys\fR,

\fBchronyd\fR/\fBntpd\fR processes as needed. Then, it waits for a signal to

kill the processes, remove the generated configuration files and exit.

.SH OPTIONS

.TP

.BI \-f " file"

Specify the path to the \fBtimemaster\fR configuration file.

.TP

.BI \-n

Don't start the programs, only print their configuration files and the commands

that would be executed if this option wasn't specified.

.TP

.BI \-l " level"

Set the maximum syslog level of messages which should be printed or sent to

the system logger. The default value is 6 (LOG_INFO).

.TP

.B \-m

Print messages to the standard output.

.TP

.B \-q

Don't send messages to the system logger.

.TP

.B \-v

Print the software version and exit.

.TP

.BI \-h

Display a help message and exit.

.SH 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.

Sections that can used in the configuration file and options that can be set in

them are described below.

.SS [timemaster]

.TP

.B ntp_program

Select which NTP implementation should be used. Possible values are

\fBchronyd\fR and \fBntpd\fR. The default value is \fBchronyd\fR. Limitations

of the implementations relevant to the timemaster configuration are listed in

\fBNOTES\fR.

.TP

.B rundir

Specify the directory where should be generated \fBchronyd\fR, \fBntpd\fR and

\fBptp4l\fR configuration files and sockets. The directory will be created if

it doesn't exist. The default value is \fB/var/run/timemaster\fR.

.TP

.B first_shm_segment

Specify the first number in a sequence of SHM segments that will be used by

\fBptp4l\fR and \fBphc2sys\fR. The default value is 0. Increasing the number

can be useful to avoid conflicts with time sources that are not started by

\fBtimemaster\fR, e.g. \fBgpsd\fR using segments number 0 and 1.

.TP

.B restart_processes

Enable or disable restarting of processes started by \fBtimemaster\fR. If the

option is set to a non-zero value, all processes except \fBchronyd\fR and

\fBntpd\fR will be automatically restarted when terminated and \fBtimemaster\fR

is running for at least one second (i.e. the process did not terminate due to a

configuration error). If a process was terminated and is not started again,

\fBtimemaster\fR will kill the other processes and exit with a non-zero status.

The default value is 1 (enabled).

.SS [ntp_server address]

The \fBntp_server\fR section specifies an NTP server that should be used as a

time source. The address of the server is included in the name of the section.

.TP

.B minpoll

.TQ

.B maxpoll

Specify the minimum and maximum NTP polling interval as powers of two in

seconds. The default values are 6 (64 seconds) and 10 (1024 seconds)

respectively. Shorter polling intervals usually improve the accuracy

significantly, but they should be used only when allowed by the operators of

the NTP service (public NTP servers generally don't allow too frequent

queries). If the NTP server is located on the same LAN, polling intervals

around 4 (16 seconds) might give best accuracy.

.TP

.B iburst

Enable or disable sending a burst of NTP packets on start to speed up the

initial synchronization. Possible values are 1 and 0. The default value is 0

(disabled).

.TP

.B ntp_options

Specify extra options that should be added for this source to the \fBserver\fR

directive in the configuration file of the selected NTP implementation. No

extra options are added by default.

.SS [ptp_domain number]

The \fBptp_domain\fR section specifies a PTP domain that should be used as a

time source. The PTP domain number is included in the name of the section. The

\fBptp4l\fR instances are configured to run in the \fBslaveOnly\fR mode. In

this section at least the \fBinterfaces\fR option needs to be set, other

options are optional.

.TP

.B interfaces

Specify which network interfaces should be used for this PTP domain. A separate

\fBptp4l\fR instance will be started for each group of interfaces sharing the

same PHC and for each interface that supports only SW time stamping. HW time

stamping is enabled automatically. If an interface with HW time stamping is

specified also in other PTP domains, only the \fBptp4l\fR instance from the

first PTP domain will be using HW time stamping.

.TP

.B ntp_poll

Specify the polling interval of the NTP SHM reference clock reading samples

from \fBptp4l\fR or \fBphc2sys\fR. It's specified as a power of two in seconds.

The default value is 2 (4 seconds).

.TP

.B phc2sys_poll

Specify the polling interval used by \fBphc2sys\fR to read a PTP clock

synchronized by \fBptp4l\fR and update the SHM sample for

\fBchronyd\fR/\fBntpd\fR. It's specified as a power of two in seconds. The

default value is 0 (1 second).

.TP

.B delay

Specify the maximum assumed roundtrip delay to the primary source of the time

in this PTP domain. This value is included in the distance used by

\fBchronyd\fR in the source selection algorithm to detect falsetickers and

assign weights for source combining. The default value is 1e\-4 (100

microseconds). With \fBntpd\fR, the \fBtos mindist\fR command can be used to

set a limit with similar purpose globally for all time sources.

.TP

.B ntp_options

Specify extra options that should be added for this source to the

\fBrefclock\fR or \fBserver\fR directives in the configuration file of the

selected NTP implementation. No extra options are added by default.

.TP

.B ptp4l_option

Specify an extra \fBptp4l\fR option specific to this PTP domain that should be

added to the configuration files generated for \fBptp4l\fR. This option may be

used multiple times in one \fBptp_domain\fR section.

.SS [chronyd]

.TP

.B path

Specify the path to the \fBchronyd\fR binary. The default value is

\fBchronyd\fR to search for the binary in \fBPATH\fR.

.TP

.B options

Specify extra options that should be added to the \fBchronyd\fR command line.

No extra options are added by default.

.SS [chrony.conf]

Settings specified in this section are copied directly to the configuration

file generated for \fBchronyd\fR. If this section is not present in the

\fBtimemaster\fR configuration file, the following setting will be added:

.EX

makestep 1 3

.EE

This configures \fBchronyd\fR to step the system clock in the first three

updates if the offset is larger than 1 second.

.SS [ntpd]

.TP

.B path

Specify the path to the \fBntpd\fR binary. The default value is \fBntpd\fR to

search for the binary in \fBPATH\fR.

.TP

.B options

Specify extra options that should be added to the \fBntpd\fR command line. No

extra options are added by default.

.SS [ntp.conf]

Settings specified in this section are copied directly to the configuration

file generated for \fBntpd\fR. If this section is not present in the

\fBtimemaster\fR configuration file, the following settings will be added:

.EX

restrict default nomodify notrap nopeer noquery

restrict 127.0.0.1

restrict ::1

.EE

This configures \fBntpd\fR to use safe default restrictions.

.SS [phc2sys]

.TP

.B path

Specify the path to the \fBphc2sys\fR binary. The default value is

\fBphc2sys\fR to search for the binary in \fBPATH\fR.

.TP

.B options

Specify extra options that should be added to all \fBphc2sys\fR command lines.

By default, \fB\-l 5\fR is added to the command lines.

.SS [ptp4l]

.TP

.B path

Specify the path to the \fBptp4l\fR binary. The default value is \fBptp4l\fR to

search for the binary in \fBPATH\fR.

.TP

.B options

Specify extra options that should be added to all \fBptp4l\fR command lines. By

default, \fB\-l 5\fR is added to the command lines.

.SS [ptp4l.conf]

Settings specified in this section are copied directly to the configuration

files generated for all \fBptp4l\fR instances. There is no default content of

this section.

.SH NOTES

For best accuracy, \fBchronyd\fR is usually preferred over \fBntpd\fR, it also

synchronizes the system clock faster. Both NTP implementations, however, have

some limitations that need to be considered before choosing the one to be used

in a given \fBtimemaster\fR configuration.

The \fBchronyd\fR limitations are:

.RS

In version 1.31 and older, the maximum number of reference clocks used at the

same time is 8. This limits the number of PHCs and interfaces using SW time

stamping that can be used for PTP.

Using polling intervals (\fBminpoll\fR, \fBmaxpoll\fR, \fBntp_poll\fR options)

shorter than 2 (4 seconds) is not recommended with versions before 1.30. With

1.30 and later values of 0 or 1 can be used for NTP sources and negative values

for PTP sources (\fBntp_poll\fR) to specify a subsecond interval.

.RE

The \fBntpd\fR limitations are:

.RS

In versions before 4.2.8p1, only the first two shared-memory segments created by

the \fBntpd\fR SHM refclock driver have owner-only access. Other segments

are created with world access, which allows any user on the system to write to

the segments and disrupt or take control over the synchronization of the clock.

In 4.2.8p1 the access was made configurable with the mode option, which is set

by \fBtimemaster\fR for owner-ownly access.

The shortest polling interval for all sources is 3 (8 seconds).

Nanosecond resolution in the SHM refclock driver is supported in version

4.2.7p303 and later, older versions have only microsecond resolution.

.RE

.SH EXAMPLES

A minimal configuration file using one NTP source and two PTP sources would be:

.EX

[ntp_server 10.1.1.1]

[ptp_domain 0]

interfaces eth0

[ptp_domain 1]

interfaces eth1

.EE

A more complex example using all \fBtimemaster\fR options would be:

.EX

[ntp_server 10.1.1.1]

minpoll 3

maxpoll 4

iburst 1

ntp_options key 12

[ptp_domain 0]

interfaces eth0 eth1

ntp_poll 0

phc2sys_poll \-2

delay 10e\-6

ntp_options prefer

ptp4l_option clock_servo linreg

ptp4l_option delay_mechanism P2P

[timemaster]

ntp_program chronyd

rundir /var/run/timemaster

first_shm_segment 1

restart_processes 0

[chronyd]

path /usr/sbin/chronyd

options

[chrony.conf]

makestep 1 3

logchange 0.5

rtcsync

driftfile /var/lib/chrony/drift

[ntpd]

path /usr/sbin/ntpd

options \-u ntp:ntp

[ntp.conf]

restrict default nomodify notrap nopeer noquery

restrict 127.0.0.1

restrict ::1

driftfile /var/lib/ntp/drift

[phc2sys]

path /usr/sbin/phc2sys

options \-l 5

[ptp4l]

path /usr/sbin/ptp4l

options

[ptp4l.conf]

logging_level 5

.EE

.SH SEE ALSO

.BR chronyd (8),

.BR ntpd (8),

.BR phc2sys (8),

.BR ptp4l (8)