NAME

exports − defines NFS file systems to be exported

SYNTAX

/etc/exports

DESCRIPTION

The /etc/exports file describes the local file systems and directories that can be mounted by remote hosts through the use of the NFS protocol. The exports file can also be used to restrict access to a particular set of remote systems. The mount request daemon mountd() accesses the exports file each time it receives a mount request from an NFS client.

Each entry in the /etc/exports file consists of a file system or directory name followed by an optional list of options and/or an optional list of identifiers that define which remote hosts can mount that particular file system or directory. The identifiers listed beside each file system or directory name can be either netgroup names or host names. When the mountd daemon receives a mount request from a client, it looks up each identifier, first in the /etc/netgroups file, and second in the /etc/hosts file. When it finds a match, mountd makes that file system or directory available to the requesting client.

The exports file format is defined as left-justified file system names, followed by any amount of white space, followed by the list of identifiers, each separated by a space. A blank identifier list beside a file system or directory name tells the mount daemon mountd to export that particular file system or directory to anyone requesting it. A number sign, ’#’, anywhere on a line specifies the beginning of a comment extending to the end of the line. White space in the left-most position of a line specifies a continuation line.

Each file system must be explicitly defined; exporting only the root, ’/’ will not allow clients to mount /usr. Exporting only /usr will not allow clients to mount /usr/local (if it is a file system). The options can only be used on file system entries. In addition, you can export individual directories within a file system.

OPTIONS

−n Special security flag does not give out the fhandle of the root of the filesystem. 
−o Export file system read only. 
−r=# Root mapping for file systems NFS client. 

EXAMPLE

/usr      alpha beta gamma  # export /usr to these hosts
/usr/staff/doe  beta        # export this directory to beta, only
/usr       clients          # export to hosts in netgroup ’clients’
/usr -o    clients          # read only
/usr/local -r=0 -n          # client maps to root, need to restrict
                              access to fhandle of root of /usr/local
      file system with -n
/usr/local                  # export to the world
/usr2     erie suez grand   # export /usr2 to these hosts

FILES

/etc/exports

SEE ALSO

hosts(5), mountd(8nfs), netgroup(5yp)
Guide to Local Area Networks