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netgroup(5) [debian man page]

netgroup(5)						      Linux Reference Manual						       netgroup(5)

netgroup - specify network groups DESCRIPTION
The netgroup file defines "netgroups", which are sets of (host, user, domain) tuples, used for permission checking when doing remote mounts, remote logins and remote shells. Each line in the file consists of a netgroup name followed by a by a list of members, where a member is either another netgroup name, or a triple: (host, user, domain) where the host, user, and domain are character strings for the corresponding components. Any of the three fields can be empty, in which case it specifies a "wildcard", or may consist of the string "-" to specify "no valid value". The domain field must either be the local domain name or empty for the netgroup entry to be used. This field does not limit the netgroup or provide security. The domain field refers to the domain in which the triple is valid, not the domain containing the the trusted host. A gateway machine should be listed under all possible hostnames by which it may be recognized: gateway (server,,) (server-sn,,) (server-bb,,) The getnetgrent functions should normally be used to access the netgroup database. FILES
/etc/netgroup SEE ALSO
getnetgrent(3), exports(5), makedbm(8), ypserv(8) WARNINGS
The triple (,,domain) allows all users and machines trusted access, and has the same effect as the triple (,,). Use the host and user fields of the triple to restrict the access correctly to a specific set of members. BUGS
The Linux libc5 does not query the /etc/netgroup file directly, it only querys the NIS server for the groups. So the netgroup database must be stored in the form of a hashed dbm database just like the passwd(5) and group(5) databases. This manpage mentions getnetgrent(3), but it seems that manpage hasn't been written yet. Since getnetgrent() is part of GNU libc it might also be that it is documented in info format. AUTHOR
Thorsten Kukuk <> NIS
May 1999 netgroup(5)

Check Out this Related Man Page

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

netgroup -- defines network groups SYNOPSIS
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 corresponding component. Any of the comma separated fields may be empty to specify a ``wildcard'' value or may consist of the string ``-'' to specify ``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. NIS
/YP INTERACTION 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 ways: o If the /etc/netgroup file does not exist, or it exists and is empty, or it exists and contains only a '+', and NIS is running, 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 platforms.) o 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 ignored). o 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 effi- cient: in particular, innetgr(3) lookups will be especially slow if the database is large. FILES
/etc/netgroup the netgroup database COMPATIBILITY
The file format is compatible with that of various vendors, however it appears that not all vendors use an identical format. SEE ALSO
getnetgrent(3), exports(5) BUGS
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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