The Network Information Service or NIS is Sun Microsystems' "Yellow Pages" (YP) client-server directory service protocol for distributing system configuration data such as user and host names between computers on a computer network.

Sun licenses this technology to virtually all other Unix vendors.

As the name "Yellow Pages" was a registered trademark in the United Kingdom of British Telecom PLC for their (paper) commercial telephone directory, Sun changed the name of their system to NIS, though all the commands and functions still start with "yp".

NIS/YP is used for keeping a central directory of users, hostnames and most other useful things in a computer network. For example, in a common UNIX environment, the list of users for Identification is placed in /etc/passwd, and secret authentication hashes in /etc/shadow. NIS adds another "global" user list which is used for identifying users on any client to the NIS system.

Technically NIS can be configured to serve 'shadow' data used to autenticate users against as well; however, not only is this cumbersome to do without resorting to DES encrypted passwords (which are known to be weak) if multiple OSs are in use, it also allows 'guests' to retrieve the whole password database for offline inspection. Kerberos was designed to handle authentication in a more secure manner.

In many environments, other directory services such as LDAP have come to replace NIS, which may be considered to be more modern and secure than NIS. As for example, the 'slapd' daemon generally runs as a non-root user, and SASL is natively supported.

The hosts/networks nameserver functionality NIS or LDAP can provide is probably better handled by DNSSEC servers when used on large LANs, leaving just site-wide identification information for NIS masters and slave machines to serve.

NIS commands

• ypcat
• ypmatch
• ypwhich
• ypclnt
• yppasswd

See also

• portmap
• TCP Wrappers
• Remote Procedure Call (RPC)
• Name Service Switch (NSS)
• Network File System (NFS)
• Domain Name System (DNS)
• Hesiod

External links

• The NIS-HOWTO from the Linux Documentation Project
• Van Emery: Distributed Authentication System (DAS) Handbook
• Solaris 8 and Debian NIS howto Tim Gibbon 2003
• Kristy Westphal: NFS and NIS Security Securityfocus article Jan. 22, 2001
• Red Hat Linux 9: Red Hat Linux Security Guide - 5.3. Securing NIS

Unix software | Sun software | Network management

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