Domain Name Service (DNS) and parser

Domain Name Service (DNS) and parser
The host is queried by the domain name and IP address. DNS is a client-server system in which the domain name interpreter accesses the Domain Name Server to link the domain name with the IP address or other suitable hosts. Gnu c Library resolver (3) can also find IP addresses in files or through Network Information Service (NIS. Some programs (such as GNOME) want the host name to be resolved to an IP address and have a valid domain name. This is really not suitable, because the host name and domain name are two completely different things. To support these software, we need to ensure that the system host name can be resolved. The common practice is to add a line of content with IP address and system Host Name in/etc/hosts. If your system has a permanent IP address, use this address; otherwise, use 127.0.0.1. 127.0.0.1 localhost127.0.1.1 uranus uses hostname -- fqdn to check whether your system's host name can be resolved to an IP address and has a valid domain name. The domain name parser is used to find the IP address corresponding to a domain name. Most common domain name Resolvers are the functions provided by resovler In gnu c Library (3 )). The other is the FireDNS resolver provided by the libfiredns software package. There are others. The DNS of gnu libc is determined by the hosts configuration in/etc/nsswitch. conf. This row lists the services used for domain name resolution, such as dns, files, nis, and nisplus. Even when files is used, the domain name parser is also controlled by the/etc/hosts configuration file. The above files are static and can be modified in your favorite editor. When the dns service is used, the behavior of the domain name interpreter is also controlled by the/etc/resolv. conf configuration file. See resolv. conf (5 ). An important feature of resolv. conf is to provide a list of IP addresses of a Domain Name Server and query these servers to obtain domain name resolution. This list is often dependent on the network environment, and the network environment changes frequently when your machine is running. Both pppd and dhclient can add or delete information in resolv. conf. However, these functions do not work normally every time and there is a conflict between the two. The resolvconf package uses a better method to solve this problem and provides a standard framework to update resolv. conf.