new "mountpoint" export option.

[nfs-utils.git] / utils / exportfs / exports.man

diff --git a/utils/exportfs/exports.man b/utils/exportfs/exports.man
index 87fd50ec2f714d91a730fc1c56d421b59936a7b4..62239441f6f8485e027b7ea33abd1401e40e56db 100644 (file)
--- a/utils/exportfs/exports.man
+++ b/utils/exportfs/exports.man
@@ -45,9 +45,10 @@ parts or those containing a single dash (\-) are ignored.
 .IP "wildcards
 Machine names may contain the wildcard characters \fI*\fR and \fI?\fR.
 This can be used to make the \fIexports\fR file more compact; for instance,
-\fI*.cs.foo.edu\fR matches all hosts in the domain \fIcs.foo.edu\fR. However,
-these wildcard characters do not match the dots in a domain name, so the
-above pattern does not include hosts such as \fIa.b.cs.foo.edu\fR.
+\fI*.cs.foo.edu\fR matches all hosts in the domain
+\fIcs.foo.edu\fR.  As these characters also match the dots in a domain
+name, the given pattern will also match all hosts within any subdomain
+of \fIcs.foo.edu\fR.
 .IP "IP networks
 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
@@ -58,7 +59,7 @@ 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
+'''.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
@@ -95,17 +96,31 @@ This can also be made explicit by using
 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
@@ -222,6 +237,25 @@ or
 '''.TP
 '''.IR link_absolute
 '''Leave all symbolic link as they are. This is the default operation.
+
+.TP
+.IR mountpoint= path
+.TP
+.I mp
+This option makes it possible to only export a directory if it has
+successfully been mounted.
+If no path is given (e.g.
+.IR mountpoint " or " mp )
+then the export point must also be a mount point.  If it isn't then
+the export point is not exported.  This allows you to be sure that the
+directory underneath a mountpoint will never be exported by accident
+if, for example, the filesystem failed to mount due to a disc error.
+
+If a path is given (e.g.
+.IR mountpoint= "/path or " mp= /path)
+then the nominted path must be a mountpoint for the exportpoint to be
+exported.
+
 .SS User ID Mapping
 .PP
 .I nfsd