Override s checking heuristics and forces it into NIS mode.
When NIS is enabled, the -l flag can be used to force passwd into "local only" mode. This flag can be used to change the entry for a local user when an NIS user exists with the same login name. For example, you will sometimes find entries for system "placeholder" users such as bin or daemon in both the NIS password maps and the local user database. By default, passwd will try to change the NIS password. The -l flag can be used to change the local password instead.
Specify what domain to use when changing an NIS password. By default, passwd assumes that the system default domain should be used. This flag is primarily for use by the superuser on the NIS master server: a single NIS server can support multiple domains. It is also possible that the domainname on the NIS master may not be set (it is not necessary for an NIS server to also be a client) in which case the passwd command needs to be told what domain to operate on.
Specify the name of an NIS server. This option, in conjunction with the -d option, can be used to change an NIS password on a non-local NIS server. When a domain is specified with the -d option and passwd is unable to determine the name of the NIS master server (possibly because the local domainname is not set), the name of the NIS master is assumed to be "localhost". This can be overridden with the -h flag. The specified hostname need not be the name of an NIS master: the name of the NIS master for a given map can be determined by querying any NIS server (master or slave) in a domain, so specifying the name of a slave server will work equally well.
Do not automatically override the password authentication checks for the super-user on the NIS master server; assume old mode instead. This flag is of limited practical use but is useful for testing.