Administration Guide

Managing NTP

|There are three attributes set for NTP during installation or you |can change them later by using SMIT or the spsitenv |command. The ntp_version attribute defaults to a value of 3, the version shipped with AIX 4.2 or later. That version of NTP is NLS-enabled. If your installation is using an earlier version of NTP, this value might need to be or might have been changed to represent the version in use. The other two attributes are described in Table 12.

Table 12. Setting time service choices

	The spsitenv Entries to Be Filled In
To do this...	ntp_config	ntp_server
Use your site's existing NTP time server to synchronize the SP system clocks.	timemaster	hostname of your current NTP time server
Use an NTP time service from the Internet to synchronize the SP system clocks.	Internet	hostnames of time servers on the Internet*
Run NTP locally on the SP to generate a consensus time.	consensus (default)
Do not use NTP on the SP. This means you are using some other independent method to synchronize system clocks.	none
Note: Change default attribute values to suit your environment. Leaving an entry blank means that you make no substitution for the default value. * See/usr/lpp/ssp/ssp.public.README for information on Internet time servers.

When you choose any of the options that involve using NTP, the installation scripts determine the IP address of the host specified as ntp_server and create the /etc/ntp.conf file on each of the control workstation, boot-install server, and processor nodes. This file indicates which hosts can provide time service to which other hosts using the designations of server and peer, where:

server: Indicates a host from which you can request time.
peer: Indicates a host with which this host can synchronize time. Either peer host can request time from the other.

The following example shows a sample /etc/ntp.conf file:

   # Server ip_addr version <ntp version>
   server 9.8.77.66 version 3      # server is host_one.conrad.ibm.com
   server 123.45.678.9 version 3   # server is host_two.ursula.ibm.com
   peer 9.8.77.55 version 3        # server is host_x.conrad.ibm.com
   peer 9.8.77.44 version 3        # server is host_y.conrad.ibm.com
   peer 9.8.77.33 version 3        # server is host_z.conrad.ibm.com

Assuming this is the /etc/ntp.conf file on your_host, the following is true:

your_host can request time from host_one, host_two, host_x, host_y, and host_z
your_host can provide time, on request, to host_x, host_y, and host_z
your_host cannot provide time to host_one or host_two.

The following table shows which host addresses will be used for servers and peers in the /etc/ntp.conf files created on the control workstation, file servers, and processor nodes for each ntp_config choice.

ntp_config	Control workstation	Boot-install servers	Processor nodes
`timemaster`	Server: Your time server Peer: All boot-install servers	Server: Your time server Peer: Control workstation Peer: All boot file servers	Server: Your time server Server: Control workstation Server: All boot file servers
`Internet`	Server: Internet server	Server: Control workstation Peer: Other boot file servers	Server: Control workstation Server: All boot file servers
`consensus`	Server: 127.127.1.10*	Server: Control workstation Peer: Other boot file servers	Server: Control workstation Server: All boot file servers
`None`	No file created	No file created	No file created
* This address signifies local time service to NTP and makes the control workstation a stratum 10 time server allowing you to hook into a higher stratum Internet time server at a later date.

Related information

For more information on the installation scripts, or to update the site environment, see the PSSP: Installation and Migration Guide.

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