yppasswd

yppasswd is a command-line utility used to change a user’s password within a Network Information Service (NIS), historically known as Yellow Pages. It is part of the NIS client tools and is used to update the password information stored in NIS maps such as passwd.byname and passwd.byuid on the NIS domain’s password map.

Operation and behavior: When invoked, yppasswd authenticates the user against the NIS password information and, if the provided credentials are valid, updates the domain’s password map with the new password. The update is performed against the NIS master server for the domain and is then propagated to slave servers according to the domain’s map refresh configuration. The command can typically be directed at a specific domain with an option such as -d and may allow specifying a particular username in some implementations; if no username is given, the operation applies to the invoking user in the current domain.

Usage notes: yppasswd commonly prompts for the current password and the new password, often requesting the new password to be entered twice for confirmation. The exact invocation syntax and options can vary between Unix-like systems and NIS implementations. In many environments, the tool assumes a trusted network and properly secured NIS infrastructure to protect password information in transit.

Security considerations: NIS passwords have historically been transmitted in plaintext over the network, making NIS-based password changes vulnerable on untrusted networks. Modern security practices favor more secure authentication systems (such as NIS+ or LDAP with TLS, Kerberos, or other centralized authentication frameworks). Administrators should implement network protections and consider upgrading to more secure alternatives where possible.

See also: ypserv, ypbind, yp-tools, NIS/NIS+ security practices.