linuxptp/timemaster.8

.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.

.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).

.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 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
Only the first two shared-memory segments created by the SHM refclock driver
in \fBntpd\fR have owner-only access. Other segments are created with world
access, possibly allowing any user on the system writing to the segments and
disrupting the synchronization.

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

[ptp_domain 0]
interfaces eth0 eth1
ntp_poll 0
phc2sys_poll -2
delay 10e-6
ptp4l_option clock_servo linreg
ptp4l_option delay_mechanism P2P

[timemaster]
ntp_program chronyd
rundir /var/run/timemaster

[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)