nfsd


SYNPOSIS
       mount -t nfsd nfsd /proc/fs/nfsd

DESCRIPTION
       The nfsd filesytem is a special filesystem which provides access to the
       Linux NFS server.  The filesystem consists of a single directory  which
       contains a number of files.  These files are actually gateways into the
       NFS server.  Writing to them can affect the server.  Reading from  them
       can provide information about the server.

       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.

       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.   If
       it  is  not  mounted,  they  will fall-back on 2.4 style functionality.
       This involves accessing the NFS server via a systemcall.  This  system-
       call is scheduled to be removed after the 2.6 kernel series.

DETAILS
       The three files in the nfsd filesystem are:

       exports
              This  file  contains  a  list  of filesystems that are currently
              exported and  clients  that  each  filesystem  is  exported  to,
              together  with a list of export options for that client/filesys-
              tem pair.  This is similar to the /proc/fs/nfs/exports  file  in
              2.4.  One difference is that a client doesn't necessarily corre-
              spond 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
              replaced 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
              handle for that path as exported to the given client.  The file-
              handles length will be at most the number of bytes given.

              The filehandle will be represented in hex with a leading '\x'.

       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
       access  permissions  that different clients have for different filesys-
       tems.  The caches are:


       auth.domain
              This cache maps the name of a client (or domain) to an  internal
              data  structure.   The  only access that is possible is to flush
              the cache.


       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
              export 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
              before that file become invalidated and  will  be  flushed  out.
              Writing  1  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).
                   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, atleast 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
              another 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.


SEE ALSO
       nfsd(8), rpc.nfsd(8), exports(5), nfsstat(8), mountd(8) exportfs(8).


AUTHOR
       NeilBrown



                                  3 July 2003                          nfsd(7)
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