ypdomainname

ypdomainname [domainname]

domainname
    Specifies the new NIS domain name to be set for the system. This action typically requires superuser (root) privileges to execute successfully.

The ypdomainname command is utilized to retrieve or assign the Network Information Service (NIS) domain name for the current host. NIS, which was originally known as Yellow Pages (YP), is an older client-server protocol developed for distributing system configuration data, such as user and host information, across a network of computers. When invoked without any arguments, ypdomainname will display the system's currently configured NIS domain name.

If a domain name is provided as an argument, the command attempts to set the new NIS domain name for the system. This operation typically requires superuser (root) privileges to modify the system's network configuration. Establishing the correct NIS domain name is critical for NIS clients to successfully locate and communicate with NIS servers on the network. While NIS has largely been superseded by modern directory services like LDAP and DNS for many contemporary use cases, ypdomainname remains a fundamental utility for managing existing NIS environments, particularly in legacy systems.

NIS is considered an older technology, and its usage has significantly declined in favor of more modern and secure directory services like LDAP and DNS. Setting the NIS domain name with ypdomainname modifies the kernel's NIS domain setting and generally requires root privileges. It is important to note that this command manages the NIS domain, which is distinct from the DNS domain used for internet name resolution.

When ypdomainname is used to set a new NIS domain name, it typically interacts with and modifies the kernel's `domainname` parameter. This parameter can also be directly inspected or modified via the `/proc/sys/kernel/domainname` file or using the sysctl command, which provides a more generic interface to kernel parameters.

It is crucial to understand that the NIS domain name managed by ypdomainname is entirely separate from the DNS (Domain Name System) domain name. The NIS domain is specifically used for internal network services like user authentication and host lookups within an NIS environment, whereas the DNS domain is utilized for global hostname resolution across the Internet and local IP networks.

NIS, initially called Yellow Pages (YP) by Sun Microsystems, was developed in the 1980s as a centralized network information service for UNIX-like systems. Due to trademark conflicts with British Telecom's 'Yellow Pages' directory, Sun subsequently renamed the service to NIS. However, many associated commands, including ypdomainname, retained the original 'yp' prefix. Its inclusion in standard UNIX distributions and later Linux systems ensured its widespread adoption, though its prominence has diminished with the advent of newer, more robust network directory services.

domainname(1), nisdomainname(1), ypserv(8), ypbind(8), ypwhich(1), ypcat(1)