netgroup man page on FreeBSD

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NETGROUP(5)		    BSD File Formats Manual		   NETGROUP(5)

     netgroup — defines network groups


     The netgroup file specifies ``netgroups'', which are sets of (host, user,
     domain) tuples that are to be given similar network access.

     Each line in the file consists of a netgroup name followed by a list of
     the members of the netgroup.  Each member can be either the name of
     another netgroup or a specification of a tuple as follows:

	   (host, user, domain)

     where the host, user, and domain are character string names for the cor‐
     responding component.  Any of the comma separated fields may be empty to
     specify a ``wildcard'' value or may consist of the string ``-'' to spec‐
     ify ``no valid value''.  The members of the list may be separated by
     whitespace and/or commas; the ``\'' character may be used at the end of a
     line to specify line continuation.	 Lines are limited to 1024 characters.
     The functions specified in getnetgrent(3) should normally be used to
     access the netgroup database.

     Lines that begin with a # are treated as comments.

     On most other platforms, netgroups are only used in conjunction with NIS
     and local /etc/netgroup files are ignored.	 With FreeBSD, netgroups can
     be used with either NIS or local files, but there are certain caveats to
     consider.	The existing netgroup system is extremely inefficient where
     innetgr(3) lookups are concerned since netgroup memberships are computed
     on the fly.  By contrast, the NIS netgroup database consists of three
     separate maps (netgroup, netgroup.byuser and netgroup.byhost) that are
     keyed to allow innetgr(3) lookups to be done quickly.  The FreeBSD
     netgroup system can interact with the NIS netgroup maps in the following

	   ·   If the /etc/netgroup file does not exist, or it exists and is
	       empty, or it exists and contains only a ‘+’, and NIS is run‐
	       ning, netgroup lookups will be done exclusively through NIS,
	       with innetgr(3) taking advantage of the netgroup.byuser and
	       netgroup.byhost maps to speed up searches.  (This is more or
	       less compatible with the behavior of SunOS and similar plat‐

	   ·   If the /etc/netgroup exists and contains only local netgroup
	       information (with no NIS ‘+’ token), then only the local
	       netgroup information will be processed (and NIS will be

	   ·   If /etc/netgroup exists and contains both local netgroup data
	       and the NIS ‘+’ token, the local data and the NIS netgroup map
	       will be processed as a single combined netgroup database.
	       While this configuration is the most flexible, it is also the
	       least efficient: in particular, innetgr(3) lookups will be
	       especially slow if the database is large.

     /etc/netgroup  the netgroup database

     The file format is compatible with that of various vendors, however it
     appears that not all vendors use an identical format.

     getnetgrent(3), exports(5)

     The interpretation of access restrictions based on the member tuples of a
     netgroup is left up to the various network applications.  Also, it is not
     obvious how the domain specification applies to the BSD environment.

     The netgroup database should be stored in the form of a hashed db(3)
     database just like the passwd(5) database to speed up reverse lookups.

BSD			       December 11, 1993			   BSD

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