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Commands Reference, Volume 4
Sets the date and time using the
Network Time Protocol (NTP). This command only applies to AIX
4.2 or later.
ntpdate [ -b ]
[ -d ] [ -s ] [ -u ] [ -a Keyid ] [ -e AuthenticationDelay ]
[ -k KeyFile ]
[ -o Version ]
[ -p Samples ]
[ -t TimeOut ]
Server ...
The ntpdate command
sets the local date and time by polling the NTP servers specified to determine
the correct time. It obtains a number of samples from each server
specified and applies the standard NTP clock filter and selection algorithms
to select the best of the samples.
The ntpdate command
makes time adjustments in one of the following ways:
- If it determines that
the clock is off by more than 0.5 seconds, it steps the clock's
time by calling the settimeofday subroutine. This is the
preferred method at boot time.
- If it determines that
the clock is off by less than 0.5 seconds, it slews the clock's
time by calling the adjtime subroutine with the offset. This
method tends to keep a badly drifting clock more accurate, though at some
expense to stability. When running the ntpdate command on a
regular basis from the cron command instead of running a daemon,
doing so once every hour or two results in precise enough timekeeping to avoid
stepping the clock.
Notes:
- The ntpdate
command's reliability and precision improves dramatically with a greater
number of servers. Although you can use a single server, you obtain
better performance by providing at least three or four servers.
- If an NTP server daemon
like the xntpd daemon is running on the same host, the
ntpdate command will decline to set the date.
- You must have root
authority on the local host to run this command.
| -a Keyid
| Authenticate all packets using Keyid.
|
| -b
| Step the clock's time by calling the settimeofday
subroutine.
|
| -d
| Specifies debug mode. Determines what results the
ntpdate command produces without actually doing them. The
results appear on the screen. This flag uses unprivileged ports.
|
| -e AuthenticationDelay
| Specifies the amount of time in seconds to delay the authentication
processing.
|
| -k KeyFile
| Specifies a different name for the file containing the keys when not
using the default /etc/ntp.keys file. See
... for the description of the KeyFile.
|
| -o Version
| Specifies the NTP version implementation to use when polling its outgoing
packets. The values for Version can be 1, 2 or 3. The
default is 3.
|
| -p Samples
| Specifies the number of samples to acquire from each server. The
values for Samples can be between 1 and 8 inclusive. The
default is 4.
|
| -s
| Specifies the use of the syslog facility to log actions instead of using
standard output. Useful when running the ntpdate command
with the cron command.
|
| -t TimeOut
| Specifies the amount of time to wait for a response. The value
given for TimeOut is rounded to a multiple of 0.2
seconds. The default is 1 second.
|
| -u
| Specifies the use of an unprivileged port to send the packets
from. Useful when you are behind a firewall that blocks incoming
traffic to privileged ports, and you want to synchronize with hosts beyond the
firewall. A firewall is a system or machine that controls the access
from outside networks to a private network.
|
| Server ...
| Specifies the servers to poll.
|
This command returns the
following exit values:
| 0
| Successful completion.
|
| >0
| An error occurred.
|
Access Control: You must
have root authority to run this command.
Auditing Events: N/A
To set the local date and time by
polling the NTP servers at address
9.3.149.107, enter:
/usr/sbin/ntpdate 9.3.149.107
Output similar to the following
appears:
28 Feb 12:09:13 ntpdate [18450]: step time server 9.3.149.107
offset 38.417792 sec
| /usr/sbin/ntpdate
| Contains the ntpdate command.
|
| /etc/ntp.keys
| Contains the default key file.
|
Commands: ntpq, ntptrace, xntpdc
Daemons: xntpd,
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