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NAME | SYNOPSIS | INTRODUCTION | DESCRIPTION | EXAMPLES | SEE ALSO | AUTHOR | COLOPHON |
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NFSREF(8) System Manager's Manual NFSREF(8)
nfsref - manage NFS referrals
nfsref [-?d] [-t type] add pathname server export [ server export
... ]
nfsref [-?d] [-t type] remove pathname
nfsref [-?d] [-t type] lookup pathname
NFS version 4 introduces the concept of file system referrals to
NFS.
A file system referral is like a symbolic link (or, symlink) to
another file system share, typically on another file server. An
NFS client, under the server's direction, mounts the referred-to
NFS export automatically when an application first accesses it.
NFSv4 referrals can be used to transparently redirect clients to
file systems that have been moved elsewhere, or to construct a
single file name space across multiple file servers. Because
file servers control the shape of the whole file name space, no
client configuration is required.
A junction is a file system object on an NFS server that, when an
NFS client encounters it, triggers a referral. Similar to a
symlink, a junction contains one or more target locations that
the server sends to clients in the form of an NFSv4 referral.
On Linux, an existing directory can be converted to a junction
and back atomically and without the loss of the directory
contents. When a directory acts as a junction, it's local
content is hidden from NFSv4 clients.
The nfsref(8) command is a simple way to get started managing
junctions and their content.
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. The nfs-fedfs type is not
used in this implementation.
For the remove and lookup subcommands, the --type option
is not required. The nfsref(8) command operates on
whatever junction contents are available.
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 add /home home.example.net /
Created junction /home.
RFC 8881 for a description of the NFS version 4 referral
mechanism
Chuck Lever <chuck.lever@oracle.com>
This page is part of the nfs-utils (NFS utilities) project.
Information about the project can be found at
⟨http://linux-nfs.org/wiki/index.php/Main_Page⟩. If you have a
bug report for this manual page, see
⟨http://linux-nfs.org/wiki/index.php/Main_Page⟩. This page was
obtained from the project's upstream Git repository
⟨git://git.linux-nfs.org/projects/steved/nfs-utils.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-05-10.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
9 Jan 2018 NFSREF(8)
Pages that refer to this page: nfsref(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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