x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
nfsd(7) Miscellaneous Information Manual nfsd(7)
NAME
nfsd - special filesystem for controlling Linux NFS server
SYNPOSIS
mount -t nfsd nfsd /proc/fs/nfsd
DESCRIPTION
The nfsd filesystem is a special filesystem which provides access to
the Linux NFS server. Writing to files in this filesystem can affect
the server. Reading from them can provide information about the
server.
As well as this filesystem, there are a collection of files in the
procfs filesystem (normally mounted at /proc) which are used to control
the NFS server. This manual page describes all of these files.
The exportfs and mountd programs (part of the nfs-utils package) expect
to find this filesystem mounted at /proc/fs/nfsd or /proc/fs/nfs.
DETAILS
Files in the nfsd filesystem include:
exports
This file contains a list of filesystems that are currently ex-
ported and clients that each filesystem is exported to, together
with a list of export options for that client/filesystem pair.
This is similar to the /proc/fs/nfs/exports file in 2.4. One
difference is that a client doesn't necessarily correspond to
just one host. It can respond to a large collection of hosts
that are being treated identically.
Each line of the file contains a path name, a client name, and a
number of options in parentheses. Any space, tab, newline or
back-slash character in the path name or client name will be re-
placed by a backslash followed by the octal ASCII code for that
character.
threads
This file represents the number of nfsd thread currently run-
ning. Reading it will show the number of threads. Writing an
ASCII decimal number will cause the number of threads to be
changed (increased or decreased as necessary) to achieve that
number.
filehandle
This is a somewhat unusual file in that what is read from it
depends on what was just written to it. It provides a transac-
tional interface where a program can open the file, write a re-
quest, and read a response. If two separate programs open,
write, and read at the same time, their requests will not be
mixed up.
The request written to filehandle should be a client name, a
path name, and a number of bytes. This should be followed by a
newline, with white-space separating the fields, and octal quot-
ing of special characters.
On writing this, the program will be able to read back a file-
handle for that path as exported to the given client. The file-
handle's length will be at most the number of bytes given.
The filehandle will be represented in hex with a leading '\x'.
clients/
This directory contains a subdirectory for each NFSv4 client.
Each file under that subdirectory gives some details about the
client in YAML format. In addition, writing "expire\n" to the
ctl file will force the server to immediately revoke all state
held by that client.
The directory /proc/net/rpc in the procfs filesystem contains a number
of files and directories. The files contain statistics that can be
display using the nfsstat program. The directories contain information
about various caches that the NFS server maintains to keep track of ac-
cess permissions that different clients have for different filesystems.
The caches are:
auth.unix.ip
This cache contains a mapping from IP address to the name of the
authentication domain that the ipaddress should be treated as
part of.
nfsd.export
This cache contains a mapping from directory and domain to ex-
port options.
nfsd.fh
This cache contains a mapping from domain and a filesystem iden-
tifier to a directory. The filesystem identifier is stored in
the filehandles and consists of a number indicating the type of
identifier and a number of hex bytes indicating the content of
the identifier.
Each directory representing a cache can hold from 1 to 3 files. They
are:
flush When a number of seconds since epoch (1 Jan 1970) is written to
this file, all entries in the cache that were last updated be-
fore that file become invalidated and will be flushed out.
Writing a time in the future (in seconds since epoch) will flush
everything. This is the only file that will always be present.
content
This file, if present, contains a textual representation of ever
entry in the cache, one per line. If an entry is still in the
cache (because it is actively being used) but has expired or is
otherwise invalid, it will be presented as a comment (with a
leading hash character).
channel
This file, if present, acts a channel for request from the ker-
nel-based nfs server to be passed to a user-space program for
handling.
When the kernel needs some information which isn't in the cache,
it makes a line appear in the channel file giving the key for
the information. A user-space program should read this, find
the answer, and write a line containing the key, an expiry time,
and the content. For example the kernel might make
nfsd 127.0.0.1
appear in the auth.unix.ip/content file. The user-space program
might then write
nfsd 127.0.0.1 1057206953 localhost
to indicate that 127.0.0.1 should map to localhost, at least for
now.
If the program uses select(2) or poll(2) to discover if it can
read from the channel then it will never see and end-of-file but
when all requests have been answered, it will block until an-
other request appears.
In the /proc filesystem there are 4 files that can be used to enabled
extra tracing of nfsd and related code. They are:
/proc/sys/sunrpc/nfs_debug
/proc/sys/sunrpc/nfsd_debug
/proc/sys/sunrpc/nlm_debug
/proc/sys/sunrpc/rpc_debug
They control tracing for the NFS client, the NFS server, the Network
Lock Manager (lockd) and the underlying RPC layer respectively. Deci-
mal numbers can be read from or written to these files. Each number
represents a bit-pattern where bits that are set cause certain classes
of tracing to be enabled. Consult the kernel header files to find out
what number correspond to what tracing.
NOTES
This file system is only available in Linux 2.6 and later series ker-
nels (and in the later parts of the 2.5 development series leading up
to 2.6). This man page does not apply to 2.4 and earlier.
Previously the nfsctl systemcall was used for communication between
nfsd and user utilities. That systemcall was removed in kernel version
3.1. Older nfs-utils versions were able to fall back to nfsctl if nec-
essary; that was removed from nfs-utils 1.3.5.
SEE ALSO
nfsd(8), rpc.nfsd(8), exports(5), nfsstat(8), mountd(8) exportfs(8).
AUTHOR
NeilBrown
3 July 2003 nfsd(7)
Want to link to this manual page? Use this URL:
<http://star2.abcm.com/cgi-bin/bsdi-man?query=nfsd&sektion=7&manpath=>