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SuSE 11.3 - man page for nfsd (suse section 7)

nfsd(7) 			 Miscellaneous Information Manual			  nfsd(7)

       nfsd - special filesystem for controlling Linux NFS server

       mount -t nfsd nfsd /proc/fs/nfsd

       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 kernels (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 (nor-
       mally  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  sys-
       temcall.  This systemcall is scheduled to be removed after the 2.6 kernel series.

       The three files in the nfsd filesystem are:

	      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 identi-

	      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.

	      This  file represents the number of nfsd thread currently running.  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 num-

	      This is a somewhat unusual file  in that what is read from it depends on	what  was
	      just written to it.  It provides a transactional interface where a program can open
	      the file, write a request, 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 num-
	      ber 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 contains a number of files and direc-
       tories.	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  filesystems.   The
       caches are:

	      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.

	      This cache contains a mapping from IP address to the  name  of  the  authentication
	      domain that the ipaddress should be treated as part of.

	      This cache contains a mapping from directory and domain to export options.

	      This  cache  contains a mapping from domain and a filesystem identifier to a direc-
	      tory.   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.

	      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 com-
	      ment (with a leading hash character).

	      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  pro-
	      gram  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
	      appear in the auth.unix.ip/content file.	The user-space program might then write
		   nfsd 1057206953 localhost
	      to indicate that should map to localhost, atleast for now.

	      If the program uses select(2) or poll(2) to discover if it can read from the  chan-
	      nel  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:
       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-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.

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


					   3 July 2003					  nfsd(7)

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