NTP (Network Time Protocol - Network Timing Protocol)
NTP is a sequential time distribution system with an excess capacity. It measures the algorithms and delays on the network and on the target machine. Using these techniques, he can synchronize clocks up to seconds. NTP settings are made from either /etc/ntp.conf or /etc/xntp.conf, depending on which distribution is used.
There are two server names in most basic configurable ntp.conf files. One is the name of the server whose clock is to be set, and the other is a fake IP address. (127.127.1.0 in this example)
The fake IP address is used in case of network problems or if the NTP server is down / crashes. When the remote NTP server gets up, the NTP application on the system will reset the system clock accordingly. The first of these two servers acts as the actual server, the second is for backup purposes. Also the location of this target file should be specified. Over time, NTP will "learn" the error rate in the system clock and adjust itself accordingly.
NTP configuration files:
The NTP configuration file /ect/ntp.conf contains the following information that the xntpd “daemon” initially used:
List of possible synchronization servers
According to what criteria to choose the synchronization server
Restrictions that the server contains when connecting to the host
Whether NTP packets will be broadcast on the network
Whether to listen to Broadcast (sent to all) NTP packets
Whether to listen to Multicast NTP packets
Driftfile file location
Whether NTP connections are displayed
Whether to allow configuration renewal to the host machine
The configuration file can be written in the desired format. Lines starting with # are comment lines. In client mode, the server controls other servers to get the current time. Once all servers are checked, the host selects which server to synchronize. To configure the server in client mode, there must be a server sentence with the name and ip address of the servers to check in the NTP configuration.
NTP operating modes:
The system can be synchronized with other servers using the xntpd “daemon” and the following methods:
Client mode
Broadcast or multicast client mode
Symmetrical active mode
Client mode: In this mode, the server checks to get the current time from other servers. After all servers are checked, the local host chooses which server to synchronize with. To configure the server in client mode, there must be a server sentence with the name and ip address to check in the NTP configuration.
Broadcast and multicast modes: In this mode, the server does not poll, it listens to all-send and multicast NTP packets on the local network.
To configure a server in one of these modes, the NTP configuration file must contain the "broadcast yes" or "multicast yes" clause. Local time servers should be configured with the send-through mode sentence configuration clause, and the send-through mode should be configured with the send-out configuration sentence. The client manager can be used to configure a server as an NTP client.
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