'\" te
.\" Copyright (C) 2003, Sun Microsystems, Inc. All Rights Reserved
.TH netgroup 4 "10 Dec 2009" "SunOS 5.11" "File Formats"
.SH NAME
netgroup \- list of network groups
.SH SYNOPSIS
.LP
.nf
\fB/etc/netgroup\fR
.fi

.SH DESCRIPTION
.sp
.LP
A \fBnetgroup\fR defines a network-wide group of hosts and users. Use a \fBnetgroup\fR to restrict access to shared \fBNFS\fR filesystems and to restrict remote login and shell access. 
.sp
.LP
Network groups are stored in a network information services, such as \fBLDAP\fR or \fBNIS\fR, not in a local file.
.sp
.LP
This manual page describes the format for a file that is used to supply input to a program such as \fBldapaddent\fR(1M) for LDAP or \fBmakedbm\fR(1M) for NIS. These programs build maps used by their corresponding network information services.
.sp
.LP
Each line of the file defines the name and membership of a network group. The line should have the format:
.sp
.in +2
.nf
\fIgroupname     member\fR... 
.fi
.in -2
.sp

.sp
.LP
The items on a line can be separated by a combination of one or more spaces or tabs.
.sp
.LP
The \fIgroupname\fR is the name of the group being defined. This is followed by a list of members of the group. Each \fImember\fR is either another group name, all of whose members are to be included in the group being defined, or a triple of the form:
.sp
.in +2
.nf
\fI(hostname,username,domainname)\fR
.fi
.in -2
.sp

.sp
.LP
In each triple, any of the three fields \fIhostname\fR, \fIusername\fR, and \fIdomainname\fR, can be empty. An empty field signifies a wildcard that matches any value in that field. Thus:
.sp
.in +2
.nf
everything (\|,\|,this.domain)
.fi
.in -2
.sp

.sp
.LP
defines a group named "everything" for the domain "this.domain" to which every host and user belongs.
.sp
.LP
The \fIdomainname\fR field refers to the domain in which the triple is valid, not the domain containing the host or user. In fact, applications using \fBnetgroup\fR generally do not check the \fIdomainname\fR. Therefore, using 
.sp
.in +2
.nf
(,,domain)
.fi
.in -2
.sp

.sp
.LP
is equivalent to 
.sp
.in +2
.nf
(,,)
.fi
.in -2
.sp

.sp
.LP
You can also use netgroups to control \fBNFS\fR mount access (see \fBshare_nfs\fR(1M)) and to control remote login and shell access (see \fBhosts.equiv\fR(4)). You can also use them to control local login access (see \fBpasswd\fR(4), \fBshadow\fR(4), and \fBcompat\fR in \fBnsswitch.conf\fR(4)).
.sp
.LP
When used for these purposes, a host is considered a member of a \fBnetgroup\fR if the \fBnetgroup\fR contains any triple in which the \fBhostname\fR field matches the name of the host requesting access and the \fBdomainname\fR field matches the domain of the host controlling access.
.sp
.LP
Similarly, a user is considered a member of a \fBnetgroup\fR if the \fBnetgroup\fR contains any triple in which the \fIusername\fR field matches the name of the \fBuser\fR requesting access and the \fIdomainname\fR field matches the domain of the host controlling access.
.sp
.LP
Note that when netgroups are used to control NFS mount access, access is granted depending only on whether the requesting host is a member of the \fBnetgroup\fR. Remote login and shell access can be controlled both on the basis of host and user membership in separate netgroups.
.SH FILES
.sp
.ne 2
.mk
.na
\fB\fB/etc/netgroup\fR\fR
.ad
.RS 17n
.rt  
Used by a network information service's utility to construct a map or table that contains \fBnetgroup\fR information. For example, \fBldapaddent\fR(1M) uses \fB/etc/netgroup\fR to construct an LDAP container.
.RE

.sp
.LP
Note that the netgroup information must always be stored in a network information service, such as \fBLDAP\fR or \fBNIS\fR. The local file is only used to construct a map or table for the network information service. It is never consulted directly.
.SH SEE ALSO
.sp
.LP
\fBldapaddent\fR(1M), \fBmakedbm\fR(1M), \fBshare_nfs\fR(1M), \fBinnetgr\fR(3C), \fBhosts\fR(4), \fBhosts.equiv\fR(4), \fBnsswitch.conf\fR(4), \fBpasswd\fR(4), \fBshadow\fR(4)
.SH NOTES
.sp
.LP
\fBnetgroup\fR requires a network information service such as \fBLDAP\fR or \fBNIS\fR.
.sp
.LP
Applications may make general membership tests using the \fBinnetgr()\fR function. See \fBinnetgr\fR(3C).
.sp
.LP
Because the "-" character will not match any specific username or hostname, it is commonly used as a placeholder that will match only wildcarded membership queries. So, for example:
.sp
.in +2
.nf
onlyhosts	(host1,-,our.domain) (host2,-,our.domain)
onlyusers	(-,john,our.domain) (-,linda,our.domain)
.fi
.in -2
.sp

.sp
.LP
effectively define netgroups containing only hosts and only users, respectively. Any other string that is guaranteed not to be a legal username or hostname will also suffice for this purpose.
.sp
.LP
Use of placeholders will improve search performance.
.sp
.LP
When a machine with multiple interfaces and multiple names is defined as a member of a \fBnetgroup\fR, one must list all of the names. See \fBhosts\fR(4). A manageable way to do this is to define a \fBnetgroup\fR containing all of the machine names. For example, for a host "gateway" that has names "gateway-subnet1" and "gateway-subnet2" one may define the \fBnetgroup\fR:
.sp
.in +2
.nf
gateway (gateway-subnet1,\|,our.domain) (gateway-subnet2,\|,our.domain)
.fi
.in -2
.sp

.sp
.LP
and use this \fBnetgroup\fR "\fBgateway\fR" whenever the host is to be included in another \fBnetgroup\fR.