The /etc/exports file contains an entry for every directory that you intend to share with NFS client machines. Each entry defines how one directory is shared. Within a UNIX filesystem, any directory may be exported to NFS clients, but once a directory has been exported, another directory lower which is under it may not be exported to a different list of clients.
The general form of an exports entry is
directory -optionlist
directory is the directory name.
optionlist is a comma separated list of option keyword or
keyword=hostlist
items. In the latter option, the hostlist is a colon separated list of
host
names or, in an NIS environment, host names and/or netgroup names, such
as
"host1:host2:...:hostn" or "host1:netgroup1".
Note that if no options are selected, the default export is read-write to all hosts. You should never name a directory without specifying at least one of the following options in the optionlist.
access=clientlist
When selected as the only option, gives read-write mount access
for only the hosts or netgroups in the client list specified.
ro
Permits read-only mount access. If the only option, all hosts are
permitted
access. To export read-only to a select client list, use
"ro,access=clientlist".
rw=clientlist
Permits read-write mount access from the clients listed. If no other
options
are selected, implies read-only access from all other hosts. To grant
read-write to one client list and read-only to another, you must
specify "rw=clientlist1,access=clientlist2".
root=hostlist
Gives root access to the root user on the specified hosts. Normally,
the
root user on the client host does not have root access in the NFS
filesystem;
requests from root on a client are translated into the user nobody on
the
server. In the special circumstances where you wish to allow root on a
client host to have root access to the filesystem on the server, you
may
include this option. For this option, the host list may not contain a
netgroup name; it must be a list of host names.