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nfsd



SYNPOSIS

       mount -t nfsd nfsd /proc/fs/nfsd


DESCRIPTION

       The nfsd filessytem 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 kernels (and in the later parts of the 2.5 develop­
       ment  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 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/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  parenthe­
              ses.  Any space, tab, newline or back-slash charac­
              ter in  the  path  name  or  client  name  will  be
              replaced by a backslash followed by the octal ASCII
              code for that character.

       threads
              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  quoting  of
              special characters.

              On  writing  this, the program will be able to read
              back a filehandle for that path as exported to  the
              given  client.   The  filehandles 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 con­
       tains a number of files and directories.  The  files  con­
       tain statistics that can be display using the nfsstat pro­
       gram.  The directories contain information  about  various
       caches  that  the  NFS  server  maintains to keep track of
       access permissions that different clients have for differ­
       ent filesystems.  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   identifier   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.

              If  an  entry  is still in the cache (because it is
              actively being used) but has expired or  is  other­
              wise  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 kernel-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,
              atleast for now.

              If the program uses select(2) or  poll(2)  to  dis­
              cover  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.  Decimal numbers can be read  from  or
       written to these files.  Each number represents a bit-pat­
       tern 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

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

  




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