.Em Note :

.Em Note :

The functionality of this program is now available

The functionality of this program is now available

in the

in the

program.

program.

See the

See the

command line

command line

option in the

option in the

page.

page.

After a suitable period of

After a suitable period of

mourning, the

mourning, the

program is to be retired from this

program is to be retired from this

distribution.

distribution.

.Pp

.Pp

sets the local date and time by polling the

sets the local date and time by polling the

Network Time Protocol (NTP) server(s) given as the

Network Time Protocol (NTP) server(s) given as the

.Ar server

.Ar server

selection algorithms are applied to select the best of these.

selection algorithms are applied to select the best of these.

Note

Note

that the accuracy and reliability of

that the accuracy and reliability of

depends on

depends on

the number of servers, the number of polls each time it is run and

the number of servers, the number of polls each time it is run and

the interval between runs.

the interval between runs.

.It Fl a Ar key

.It Fl a Ar key

Enable the authentication function and specify the key

Enable the authentication function and specify the key

identifier to be used for authentication as the argument

identifier to be used for authentication as the argument

The keys and key identifiers must match

The keys and key identifiers must match

in both the client and server key files.

in both the client and server key files.

The default is to disable

The default is to disable

if the offset is

if the offset is

greater than +-128 ms.

greater than +-128 ms.

Note that, if the offset is much greater

Note that, if the offset is much greater

slew the clock to the correct value.

slew the clock to the correct value.

should not be used to synchronize clients.

should not be used to synchronize clients.

.It Fl b

.It Fl b

Force the time to be stepped using the

Force the time to be stepped using the

time.

time.

.It Fl d

.It Fl d

Enable the debugging mode, in which

Enable the debugging mode, in which

will go

will go

through all the steps, but not adjust the local clock.

through all the steps, but not adjust the local clock.

Information

Information

.Ar authdelay ,

.Ar authdelay ,

in seconds and fraction

in seconds and fraction

(see

(see

for details).

for details).

This number is usually small

This number is usually small

enough to be negligible for most purposes, though specifying a

enough to be negligible for most purposes, though specifying a

.Pa /etc/ntp.keys .

.Pa /etc/ntp.keys .

This file

This file

should be in the format described in

should be in the format described in

.It Fl o Ar version

.It Fl o Ar version

Specify the NTP version for outgoint packets as the integer

Specify the NTP version for outgoint packets as the integer

.Ar version ,

.Ar version ,

which can be 1 or 2.

which can be 1 or 2.

The default is 3.

The default is 3.

This allows

This allows

to be used with older NTP versions.

to be used with older NTP versions.

.It Fl p Ar samples

.It Fl p Ar samples

Specify the number of samples to be acquired from each server

Specify the number of samples to be acquired from each server

.It Fl s

.It Fl s

Divert logging output from the standard output (default) to the

Divert logging output from the standard output (default) to the

system

system

facility.

facility.

This is designed primarily for

This is designed primarily for

convenience of

convenience of

scripts.

scripts.

.It Fl t Ar timeout

.It Fl t Ar timeout

Specify the maximum time waiting for a server response as the

Specify the maximum time waiting for a server response as the

value

value

.Ar timeout ,

.Ar timeout ,

in seconds and fraction.

in seconds and fraction.

rounded to a multiple of 0.2 seconds.

rounded to a multiple of 0.2 seconds.

The default is 1 second, a

The default is 1 second, a

value suitable for polling across a LAN.

value suitable for polling across a LAN.

.It Fl u

.It Fl u

Direct

Direct

packets.

packets.

This is most useful when behind a firewall that blocks

This is most useful when behind a firewall that blocks

incoming traffic to privileged ports, and you want to synchronise

incoming traffic to privileged ports, and you want to synchronise

with hosts beyond the firewall.

with hosts beyond the firewall.

Note that the

Note that the

option

option

always uses unprivileged ports.

always uses unprivileged ports.

.It Fl v

.It Fl v

identification string to be logged.

identification string to be logged.

.El

.El

.Pp

.Pp

can be run manually as necessary to set the

can be run manually as necessary to set the

host clock, or it can be run from the host startup script to set

host clock, or it can be run from the host startup script to set

the clock at boot time.

the clock at boot time.

This is useful in some cases to set the

This is useful in some cases to set the

clock initially before starting the NTP daemon

clock initially before starting the NTP daemon

It is

It is

also possible to run

also possible to run

from a

from a

script.

script.

However, it is important to note that

However, it is important to note that

with

with

contrived

contrived

scripts is no substitute for the NTP

scripts is no substitute for the NTP

daemon, which uses sophisticated algorithms to maximize accuracy

daemon, which uses sophisticated algorithms to maximize accuracy

and reliability while minimizing resource use.

and reliability while minimizing resource use.

Finally, since

Finally, since

does not discipline the host clock frequency as

does not discipline the host clock frequency as

does

does

the accuracy using

the accuracy using

is

is

limited.

limited.

.Pp

.Pp

Time adjustments are made by

Time adjustments are made by

in one of two

in one of two

ways.

ways.

If

If

determines the clock is in error more

determines the clock is in error more

than 0.5 second it will simply step the time by calling the system

than 0.5 second it will simply step the time by calling the system

.Xr settimeofday 2

.Xr settimeofday 2

The latter technique is less disruptive

The latter technique is less disruptive

and more accurate when the error is small, and works quite well

and more accurate when the error is small, and works quite well

when

when

is run by

is run by

every hour or

every hour or

two.

two.

.Pp

.Pp

will decline to set the date if an NTP server

will decline to set the date if an NTP server

daemon (e.g.,

daemon (e.g.,

is running on the same host.

is running on the same host.

When

When

running

running

on a regular basis from

on a regular basis from

as

as

an alternative to running a daemon, doing so once every hour or two

an alternative to running a daemon, doing so once every hour or two

will result in precise enough timekeeping to avoid stepping the

will result in precise enough timekeeping to avoid stepping the

If NetInfo support is compiled into

If NetInfo support is compiled into

.Nm , 

.Nm , 

then the

then the

argument is optional if

argument is optional if

can find a

can find a

time server in the NetInfo configuration for

time server in the NetInfo configuration for

.Sh FILES

.Sh FILES

.Bl -tag -width /etc/ntp.keys -compact

.Bl -tag -width /etc/ntp.keys -compact

.It Pa /etc/ntp.keys

.It Pa /etc/ntp.keys