.PP
The file format is similar to the SunOS
.I exports
-file, except that several additional options are permitted. Each line
-contains an export point and a list of machine or netgroup names allowed
-to mount the file system at that point. An optional parenthesized list
-of export parameters may follow each machine name. Blank lines are
-ignored, and a # introduces a comment to the end of the line. Entries may
-be continued across newlines using a backslash.
+file. Each line contains an export point and a whitespace-separated list
+of clients allowed to mount the file system at that point. Each listed
+client may be immediately followed by a parenthesized, comma-separated
+list of export options for that client. No whitespace is permitted
+between a client and its option list.
+.PP
+Blank lines are ignored. A pound sign ("#") introduces a comment to the
+end of the line. Entries may be continued across newlines using a
+backslash. If an export name contains spaces it should be quoted using
+double quotes. You can also specify spaces or other unusual character in
+the export name using a backslash followed by the character code as three
+octal digits.
.PP
.SS Machine Name Formats
NFS clients may be specified in a number of ways:
You can also export directories to all hosts on an IP (sub-) network
simultaneously. This is done by specifying an IP address and netmask pair
as
-.IR address/netmask .
-.TP
+.IR address/netmask
+where the netmask can be specified in dotted-decimal format, or as a
+contiguous mask length (for example, either `/255.255.252.0' or `/22' appended
+to the network base address result in identical subnetworks with 10 bits of
+host). Wildcard characters generally do not work on IP addresses, though they
+may work by accident when reverse DNS lookups fail.
+'''.TP
'''.B =public
'''This is a special ``hostname'' that identifies the given directory name
'''as the public root directory (see the section on WebNFS in
the
.IR ro " option.
.TP
-.IR sync
-This option requests that all file writes be committed to disc before
-the write request completes. This is required for complete safety of
-data in the face of a server crash, but incurs a performance hit.
-The default is to allow the server to write the data out whenever it
-is ready. This can be explicitly requested with the
-.IR async " option.
+.IR async
+This option allows the NFS server to violate the NFS protocol and
+reply to requests before any changes made by that request have been
+committed to stable storage (e.g. disc drive).
+
+Using this option usually improves performance, but at the cost that
+an unclean server restart (i.e. a crash) can cause data to be lost or
+corrupted.
+
+In releases of nfs-utils upto and including 1.0.0, this option was the
+default. In this and future releases,
+.I sync
+is the default, and
+.I async
+must be explicit requested if needed.
+To help make system adminstrators aware of this change, 'exportfs'
+will issue a warning if neither
+.I sync
+nor
+.I async
+is specified.
.TP
.IR no_wdelay
-This option only has effect if
-.I sync
+This option has no effect if
+.I async
is also set. The NFS server will normally delay committing a write request
to disc slightly if it suspects that another related write request may be in
progress or may arrive soon. This allows multiple write requests to
'''# Mapping for client foobar:
'''# remote local
'''uid 0-99 - # squash these
-'''uid 100-500 1000 # map 100-500 to 1000-1500
+'''uid 100-500 1000 # map 100-500 to 1000-1400
'''gid 0-49 - # squash these
'''gid 50-100 700 # map 50-100 to 700-750
'''.fi
projects / nfs-utils.git / blobdiff