Document fsid=

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

diff --git a/utils/exportfs/exports.man b/utils/exportfs/exports.man
index 97264cdc6511880f69ed3d00a0c092043b1abffd..034a896225e09c84001e9365b941397b54350306 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
@@ -236,6 +237,47 @@ 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.
+
+.TP
+.IR fsid= num
+This option forces the filesystem identification portion of the file
+handle and file attributes used on the wire to be
+.I num
+instead of a number derived from the major and minor number of the
+block device on which the filesystem is mounted.  Any 32 bit number
+can be used, but it must be unique amongst all the exported filesystems.
+
+This can be useful for NFS failover, to ensure that both servers of
+the failover pair use the same NFS file handles for the shared filesystem
+thus avoiding stale file handles after failover.
+
+Some Linux filesystems are not mounted on a block device; exporting
+these via NFS requires the use of the
+.I fsid
+option (although that may still not be enough).
+
+The value  0 has a special meaning when use with NFSv4.  NFSv4 has a
+concept of a root of the overall exported filesystem. The export point
+exported with fsid=0 will be used as this root.
+
 .SS User ID Mapping
 .PP
 .I nfsd