NFSREF
Section: Maintenance Commands (8)
Updated: 9 Jan 2018
Page Index
NAME
nfsref - manage NFS referrals
SYNOPSIS
nfsref
[
-?d]
[
-t
type]
add
pathname server export
[
server
export ... ]
nfsref
[-?d]
[-t
type]
remove
pathname
nfsref
[-?d]
[-t
type]
lookup
pathname
INTRODUCTION
NFS version 4 introduces the concept of
file system referrals
to NFS.
A file system referral is like a symbolic link on a file server
to another file system share, possibly on another file server.
On an NFS client, a referral behaves like an automounted directory.
The client, under the server's direction, mounts a new NFS export
automatically when an application first accesses that directory.
Referrals are typically used to construct a single file name space
across multiple file servers.
Because file servers control the shape of the name space,
no client configuration is required,
and all clients see the same referral information.
The Linux NFS server supports NFS version 4 referrals.
Administrators can specify the
refer=
export option in
/etc/exports
to configure a list of exports from which the client can choose.
See
exports(5)
for details.
DESCRIPTION
The
nfsref(8)
command is a simple way to get started managing junction metadata.
Other administrative commands provide richer access to junction information.
Subcommands
Valid
nfsref(8)
subcommands are:
- add
-
Adds junction information to the directory named by
pathname.
The named directory must already exist,
and must not already contain junction information.
Regular directory contents are obscured to NFS clients by this operation.
-
A list of one or more file server and export path pairs
is also specified on the command line.
When creating an NFS basic junction, this list is
stored in an extended attribute of the directory.
-
If junction creation is successful, the
nfsref(8)
command flushes the kernel's export cache
to remove previously cached junction information.
- remove
-
Removes junction information from the directory named by
pathname.
The named directory must exist,
and must contain junction information.
Regular directory contents are made visible to NFS clients again by this operation.
-
If junction deletion is successful, the
nfsref(8)
command flushes the kernel's export cache
to remove previously cached junction information.
- lookup
-
Displays junction information stored in the directory named by
pathname.
The named directory must exist,
and must contain junction information.
-
When looking up an NFS basic junction, the junction information
in the directory is listed on
stdout.
Command line options
- -d, --debug
-
Enables debugging messages during operation.
- -t, --type=
junction-type -
Specifies the junction type for the operation. Valid values for
junction-type
are
nfs-basic
or
nfs-fedfs.
-
For the
add
subcommand, the default value if this option is not specified is
nfs-basic.
For the
remove
and
lookup
subcommands, the
--type
option is not required. The
nfsref(8)
command operates on whatever junction contents are available.
EXAMPLES
Suppose you have two file servers,
top.example.net
and
home.example.net.
You want all your clients to mount
top.example.net:/
and then see the files under
home.example.net:/
automatically in
top:/home.
On
top.example.net,
you might issue this command as root:
-
# mkdir /home
# nfsref --type=nfs-basic add /home home.example.net /
Created junction /home.
FILES
- /etc/exports
-
NFS server export table
SEE ALSO
exports(5)
RFC 5661 for a description of NFS version 4 referrals
AUTHOR
Chuck Lever <
chuck.lever@oracle.com>