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       rpc.mountd - NFS mount daemon


       /usr/sbin/rpc.mountd [options]


       The   rpc.mountd  program  implements  the  NFS  mount  protocol.  When
       receiving a MOUNT request from an NFS client,  it  checks  the  request
       against  the  list of currently exported file systems. If the client is
       permitted to mount the file system, rpc.mountd obtains  a  file  handle
       for requested directory and returns it to the client.

   Exporting NFS File Systems
       Making file systems available to NFS clients is called exporting.

       Usually, a file system and the hosts it should be made available to are
       listed in the /etc/exports file, and invoking exportfs -a whenever  the
       system  is  booted.  The  exportfs(8)  command makes export information
       available to both the kernel  NFS  server  module  and  the  rpc.mountd

       Alternatively,  you can export individual directories temporarily using
       exportfs’s host:/directory syntax.

   The rmtab File
       For every mount request received from an NFS client, rpc.mountd adds an
       entry  to  the  /var/lib/nfs/rmtab  file.  When  receiving  an  unmount
       request, that entry is removed.

       However, this file is mostly ornamental. One, the client  can  continue
       to  use  the  file  handle  even  after  calling  rpc.mountds UMOUNT
       procedure. And two, if a client reboots without notifying rpc.mountd  ,
       a stale entry will remain in rmtab.


       -d kind  or  --debug kind
              Turn on debugging. Valid kinds are: all, auth, call, general and

       -F  or  --foreground
              Run in foreground (do not daemonize)

       -f  or  --exports-file
              This option specifies the exports file, listing the clients that
              this server is prepared to serve and parameters to apply to each
              such mount (see exports(5)).  By default, export information  is
              read from /etc/exports.

       -h  or  --help
              Display usage message.

       -o num  or  --descriptors num
              Set the limit of the number of open file descriptors to num. The
              default is to leave the limit unchanged.

       -N  or  --no-nfs-version
              This option can be used to request that rpc.mountd do not  offer
              certain  versions  of NFS. The current version of rpc.mountd can
              support both NFS version 2 and the newer version 3. If  the  NFS
              kernel module was compiled without support for NFSv3, rpc.mountd
              must be invoked with the option --no-nfs-version 3 .

       -n  or  --no-tcp
              Don’t advertise TCP for mount.

       -P     Ignored (compatibility with unfsd??).

       -p  or  --port num
              Force rpc.mountd to bind to the specified port num,  instead  of
              using the random port number assigned by the portmapper.

       -H  or  --ha-callout prog
              Specify  a high availability callout program, which will receive
              callouts for all client mount and unmount requests. This  allows
              rpc.mountd  to  be  used  in  a  High  Availability NFS (HA-NFS)
              environment. This callout is not needed (and should not be used)
              with  2.6  and later kernels (instead, mount the nfsd filesystem
              on  /proc/fs/nfsd  ).   The  program  will  be  called  with   4
              arguments.   The first will be mount or unmount depending on the
              reason for the callout.  The second will  be  the  name  of  the
              client  performing  the  mount.  The third will be the path that
              the client is mounting.  The last is the  number  of  concurrent
              mounts that we believe the client has of that path.

       -s, --state-directory-path directory
              specify  a  directory in which to place statd state information.
              If this option is not specified the default of  /var/lib/nfs  is

       -r, --reverse-lookup
              mountd tracks IP addresses in the rmtab, and when a DUMP request
              is made (by someone running  showmount  -a,  for  instance),  it
              returns  IP  addresses  instead  of  hostnames  by default. This
              option causes mountd to do a reverse lookup on each  IP  address
              and  return  that  hostname  instead.  Enabling  this can have a
              substantial negative effect on performance in some situations.

       -t N or --num-threads=N
              This  option  specifies  the  number  of  worker  threads   that
              rpc.mountd  spawns.   The default is 1 thread, which is probably
              enough.  More threads are usually only needed  for  NFS  servers
              which need to handle mount storms of hundreds of NFS mounts in a
              few seconds, or when your DNS server is slow or unreliable.

       -V  or  --nfs-version
              This option can be used to request that rpc.mountd offer certain
              versions  of  NFS. The current version of rpc.mountd can support
              both NFS version 2 and the newer version 3.

       -v  or  --version
              Print the version of rpc.mountd and exit.

       -g  or  --manage-gids
              Accept requests from the kernel to  map  user  id  numbers  into
              lists  of  group  id  numbers for use in access control.  An NFS
              request will normally  (except  when  using  Kerberos  or  other
              cryptographic  authentication)  contains a user-id and a list of
              group-ids.  Due to a limitation in the NFS protocol, at most  16
              groups ids can be listed.  If you use the -g flag, then the list
              of group ids received from the client will be replaced by a list
              of  group ids determined by an appropriate lookup on the server.
              Note that the ’primary’ group id is not affected so  a  newgroup
              command  on  the  client will still be effective.  This function
              requires a Linux Kernel with version at least 2.6.21.


       This rpc.mountd version is protected by the  tcp_wrapper  library.  You
       have to give the clients access to rpc.mountd if they should be allowed
       to use it. To allow connects from clients of the  domain  you
       could use the following line in /etc/hosts.allow:


       You have to use the daemon name mountd for the daemon name (even if the
       binary has a different name).  Note: hostnames used  in  either  access
       file will be ignored when they can not be resolved into IP addresses.

       For  further  information  please  have  a  look  at  the  tcpd(8)  and
       hosts_access(5) manual pages.


       rpc.nfsd(8), exportfs(8), exports(5), rpc.rquotad(8).


       /etc/exports, /var/lib/nfs/xtab.


       Olaf Kirch, H. J. Lu, G. Allan Morris III, and a host of others.

                                  31 Aug 2004                    rpc.mountd(8)