Use UUIDs to identify filesystems if kernel supports it.

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

diff --git a/utils/exportfs/exports.man b/utils/exportfs/exports.man
index 55bd36441f4a2dfbe3cadc6617ef2d8f07d98435..3aa8de8ab45b6af86d842c6f502929318556c39e 100644 (file)
--- a/utils/exportfs/exports.man
+++ b/utils/exportfs/exports.man
@@ -22,6 +22,11 @@ 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
 list of export options for that client. No whitespace is permitted
 between a client and its option list.
 .PP

+Also, each line may have one or more specifications for default options
+after the path name, in the form of a dash ("\-") followed by an option
+list. The option list is used for all subsequent exports on that line
+only.
+.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
 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


@@ -88,7 +93,7 @@ rpcsec_gss and to make requirements on the IP address of the client.
 understands the following export options:
 .TP
 .IR secure "\*d
 understands the following export options:
 .TP
 .IR secure "\*d

-This option requires that requests originate on an internet port less
+This option requires that requests originate on an Internet port less

 than IPPORT_RESERVED (1024). This option is on by default. To turn it
 off, specify
 .IR insecure .
 than IPPORT_RESERVED (1024). This option is on by default. To turn it
 off, specify
 .IR insecure .


@@ -116,13 +121,13 @@ storage (see
 .IR async
 above).
 
 .IR async
 above).
 

-In releases of nfs-utils upto and including 1.0.0, this option was the
-default.  In this and future releases,
+In releases of nfs-utils up to and including 1.0.0, this option was the
+default.  In all subsequence releases,

 .I sync
 is the default, and
 .I async
 .I sync
 is the default, and
 .I async

-must be explicit requested if needed.
-To help make system adminstrators aware of this change, 'exportfs'
+must be explicitly requested if needed.
+To help make system administrators aware of this change, 'exportfs'

 will issue a warning if neither
 .I sync
 nor
 will issue a warning if neither
 .I sync
 nor


@@ -217,6 +222,16 @@ The default of having subtree checks enabled, can be explicitly
 requested with
 .IR subtree_check .
 
 requested with
 .IR subtree_check .
 

+From release 1.1.0 of nfs-utils onwards, the default will be
+.I no_subtree_check
+as subtree_checking tends to cause more problems than it is worth.
+If you genuinely require subtree checking, you should explicitly put
+that option in the
+.B exports
+file.  If you put neither option,
+.I exportfs
+will warn you that the change is pending.
+

 .TP
 .IR insecure_locks
 .TP
 .TP
 .IR insecure_locks
 .TP


@@ -287,30 +302,37 @@ 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)
 
 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
+then the nominated path must be a mountpoint for the exportpoint to be

 exported.
 
 .TP
 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.
+.IR fsid= num|root|uuid
+NFS needs to be able to identify each filesystem that it exports.
+Normally it will use a UUID for the filesystem (if the filesystem has
+such a thing) or the device number of the device holding the
+filesystem (if the filesystem is stored on the device).

 
 

-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.
+As not all filesystems are stored on devices, and not all filesystems
+have UUIDs, it is sometimes necessary to explicitly tell NFS how to
+identify a filesystem.  This is done with the
+.I fsid=
+option.
+
+For NFSv4, there is a distinguished filesystem which is the root of
+all exported filesystem.  This is specified with
+.I fsid=root
+or
+.I fsid=0
+both of which mean exactly the same thing.

 
 

-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).
+Other filesystems can be identified with a small integer, or a UUID
+which should contain 32 hex digits and arbitrary punctuation.

 
 

-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.
+Linux kernels version 2.6.20 and earlier do not understand the UUID
+setting so a small integer must be used if an fsid option needs to be
+set for such kernels.  Setting both a small number and a UUID is
+supported so the same configuration can be made to work on old and new
+kernels alike.

 
 .SS User ID Mapping
 .PP
 
 .SS User ID Mapping
 .PP


@@ -392,8 +414,11 @@ Here's the complete list of mapping options:
 .TP
 .IR root_squash
 Map requests from uid/gid 0 to the anonymous uid/gid. Note that this does
 .TP
 .IR root_squash
 Map requests from uid/gid 0 to the anonymous uid/gid. Note that this does

-not apply to any other uids that might be equally sensitive, such as user
-.IR bin .
+not apply to any other uids or gids that might be equally sensitive, such as
+user
+.IR bin 
+or group
+.IR staff .

 .TP
 .IR no_root_squash
 Turn off root squashing. This option is mainly useful for diskless clients.
 .TP
 .IR no_root_squash
 Turn off root squashing. This option is mainly useful for diskless clients.


@@ -486,6 +511,7 @@ is supposedly that of user joe).
 /usr            *.local.domain(ro) @trusted(rw)
 /home/joe       pc001(rw,all_squash,anonuid=150,anongid=100)
 /pub            (ro,insecure,all_squash)
 /usr            *.local.domain(ro) @trusted(rw)
 /home/joe       pc001(rw,all_squash,anonuid=150,anongid=100)
 /pub            (ro,insecure,all_squash)

+/srv/www        \-sync,rw server @trusted @external(ro)

 '''/pub/private    (noaccess)
 .fi
 .PP
 '''/pub/private    (noaccess)
 .fi
 .PP


@@ -499,6 +525,9 @@ under the nobody account. The
 .I insecure 
 option in this entry also allows clients with NFS implementations that
 don't use a reserved port for NFS.
 .I insecure 
 option in this entry also allows clients with NFS implementations that
 don't use a reserved port for NFS.

+The sixth line exports a directory read-write to the machine 'server'
+as well as the `@trusted' netgroup, and read-only to netgroup `@external',
+all three mounts with the `sync' option enabled.

 ''' The last line denies all NFS clients
 '''access to the private directory.
 '''.SH CAVEATS
 ''' The last line denies all NFS clients
 '''access to the private directory.
 '''.SH CAVEATS