UNIX for Dummies Questions & Answers

In /etc/passwd you could have entries of the form +user or +@netgroup (include the specified user from the NIS passwd map), -user or -@netgroup (exclude the specified user) and + (include every user, except the excluded ones, from the NIS passwd map). Since most people only put a + at the end of /etc/passwd to include everything from NIS, the switch provides a faster native for this case (`passwd: files nis') which doesn't require the single + entry in etc/passwd, /etc/group and /etc/shadow. If this is not sufficient, the NSS `compat' service provides full +/- semantics. By default, the source is `nis', but this may be overriden by specifying `nisplus' as source for the pseudo-databases passwd_compat, group_compat and shadow_compat.