Using NTP Time Services

Network Time Protocol (NTP) synchronizes your machine time with a centralized time server of your choosing. Time servers available on the Internet are usually a secondary source to a machine that acts as a central time server. Central (or primary) time servers are usually linked into an extremely accurate clock mechanism. To specify an NTP time source, select the Network Service icon in the left pane after starting YaST, and then select the NTP Client option from the right pane, or type yast2 ntp-client.

Selecting the NTP Client option causes you to be prompted for the host name of an NTP source (see Figure 9-9). If you have an NTP source set up on the local network, you can use it here. Alternatively, you can either choose a particular public NTP server, or make use of the ntp.org's pool system by choosing "Use random servers from pool.ntp.org." This sets up three servers — O.pool.ntp.org, l.pool.ntp.org and 2.pool.ntp.org — as time sources. These are actually aliases for time servers that have joined ntp.org's pool system. By choosing "Advanced Configuration" you can, if you wish, add any number of time servers of your own choice. If you are in the UK, for instance, you might wish to add members of ntp.org's UK pool such as O.uk.pool.ntp.org here. To ensure that your system automatically synchronizes itself with an NTP server, you should select the When Booting System option button — the default selection is Never, which effectively disables the use of NTP by your system.

It is customary to source your NTP synchronization to a secondary time server, and for primary servers to synchronize to secondary servers only for general use.

FIGURE 9-9

Configuring an NTP source

FIGURE 9-9

Configuring an NTP source

p : tj If your system gets its address by DHCP, and if the DHCP server offers time server i i".-.,".\'CV..\*:information, you can choose to use whatever NTP server the DHCP server references by choosing ''Configure NTP daemon via DCHP'' in the Advanced dialog.

As with most YaST modules, what happens behind the scenes here is that the module writes to certain configuration files. In the case of NTP, the YaST module writes to /etc/sysconfig/ntp and to the actual configuration file for the NTP daemon which is /etc/ntp.conf. It is instructive to look at these files before and after running the module.

Was this article helpful?

0 0

Post a comment