As soon as multiple UNIX systems in a network access common resources, it
becomes imperative that all user and group identities are the same for
all machines in that network. The network should be transparent to users:
their environments should not vary, regardless of which machine they are
actually using. This can be done by means of NIS and NFS services. NFS
distributes file systems over a network and is discussed in
Section 27.0, Sharing File Systems with NFS,
(↑ Administration Guide ).
NIS (Network Information Service) can be described as a database-like
service that provides access to the contents of
/etc/passwd, /etc/shadow, and
/etc/group across networks. NIS can also be used for
other purposes (making the contents of files like
/etc/hosts or /etc/services
available, for example), but this is beyond the scope of this
introduction. People often refer to NIS as YP,
because it works like the network's yellow pages.