mount_nfs - mount remote NFS resources


     mount [ -F  nfs] [generic_options] [-o specific_options]  [-
     O] resource

     mount [ -F  nfs] [generic_options] [-o specific_options]  [-
     O] mount_point

     mount [ -F  nfs] [generic_options] [-o specific_options]  [-
     O] resource mount_point


     The mount utility attaches a named resource to the file sys-
     tem  hierarchy  at  the pathname location mount_point, which
     must already exist. If mount_point has any contents prior to
     the  mount  operation,  the contents remain hidden until the
     resource is once again unmounted.

     If the resource is listed in the /etc/vfstab file, the  com-
     mand  line  can  specify either resource or mount_point, and
     mount consults /etc/vfstab for more information. If  the  -F
     option  is  omitted,  mount  takes the file system type from

     If the resource is not listed in the /etc/vfstab file,  then
     the  command  line  must  specify  both the resource and the

     host can  be  an  IPv4  or  IPv6  address  string.  As  IPv6
     addresses  already contain colons, enclose host in a pair of
     square brackets when specifying an IPv6 address string. Oth-
     erwise the first occurrence of a colon can be interpreted as
     the separator between the host name and path,  for  example,
     [1080::8:800:200C:417A]:tmp/file.     See    inet(7P)    and

           Where host is the name of the  NFS  server  host,  and
           pathname  is  the  path  name  of the directory on the
           server being mounted.  The path  name  is  interpreted
           according  to the server's path name parsing rules and
           is not necessarily  slash-separated,  though  on  most
           servers, this is the case.

           This is an NFS URL and follows the standard convention
           for NFS URLs as described in NFS URL Scheme, RFC 2224.
           See the discussion of  URL's  and  the  public  option
           under NFS FILE SYSTEMS for a more detailed discussion.

nfs://host[:port]/pathname resources

     A    comma-
           separated     list     of     host:pathname     and/or
           See the discussion  of  replicated  file  systems  and
           failover  under  NFS  FILE SYSTEMS for a more detailed

     A comma-
           separated list of hosts followed by a :pathname suffix
           See the discussion  of  replicated  file  systems  and
           failover  under  NFS  FILE SYSTEMS for a more detailed

     The mount command maintains a table of mounted file  systems
     in /etc/mnttab, described in mnttab(4).


     See mount(1M) for the list of supported generic_options.

     -o specific_options
           Set  file  system  specific  options  according  to  a
           comma-separated list with no intervening spaces.

                 Hold  cached  attributes  for  no  more  than  n
                 seconds  after  directory  update.  The  default
                 value is 60.

                 Hold cached attributes for at  least  n  seconds
                 after directory update. The default value is 30.

                 Hold  cached  attributes  for  no  more  than  n
                 seconds  after  file  modification.  The default
                 value is 60.

                 Hold cached attributes for at  least  n  seconds
                 after file modification. The default value is 3.

                 Set min and max  times  for  regular  files  and
                 directories to n seconds.

           bg | fg
                 If the first attempt fails, retry in  the  back-
                 ground,  or,  in  the foreground. The default is

           forcedirectio | noforcedirectio
                 If forcedirectio  is  specified,  then  for  the
                 duration  of  the  mount,  forced  direct I/O is
                 used. If the filesystem is  mounted  using  for-
                 cedirectio, data is transferred directly between
                 client and server,  with  no  buffering  on  the
                 client.  If  the  filesystem  is  mounted  using
                 noforcedirectio, data is buffered on the client.
                 forcedirectio is a performance option that is of
                 benefit only in large sequential data transfers.
                 The default behavior is noforcedirectio.

           grpid By default, the  GID  associated  with  a  newly
                 created  file obeys the System V semantics; that
                 is, the GID is set to the effective GID  of  the
                 calling process. This behavior may be overridden
                 on a per-directory basis by setting the  set-GID
                 bit  of  the parent directory; in this case, the
                 GID of a newly created file is set to the GID of
                 the parent directory (see open(2) and mkdir(2)).
                 Files created on file systems that  are  mounted
                 with   the  grpid  option  obeys  BSD  semantics
                 independent of whether the set-GID  bit  of  the
                 parent  directory  is  set;  that is, the GID is
                 unconditionally  inherited  from  that  of   the
                 parent directory.

           hard | soft
                 Continue to  retry  requests  until  the  server
                 responds  (hard)  or give up and return an error
                 (soft). The default value is hard.

           intr | nointr
                 Allow (do not allow) keyboard interrupts to kill
                 a  process  that  is  hung  while  waiting for a
                 response on  a  hard-mounted  file  system.  The
                 default  is  intr,  which  makes it possible for
                 clients to interrupt applications  that  may  be
                 waiting for a remote mount.

           noac  Suppress data and attribute  caching.  The  data
                 caching  that is suppressed is the write-behind.
                 The local page cache is  still  maintained,  but
                 data  copied  into  it is immediately written to
                 the server.

           nocto Do not perform  the  normal  close-to-open  con-
                 sistency.  When  a  file is closed, all modified
                 data associated with the file is flushed to  the
                 server  and  not held on the client. When a file
                 is opened the client  sends  a  request  to  the
                 server  to  validate  the client's local caches.
                 This  behavior  ensures  a  file's   consistency
                 across  multiple  NFS clients. When -nocto is in
                 effect, the client does not perform the flush on
                 close  and  the request for validation, allowing
                 the possiblity of differences  among  copies  of
                 the same file as stored on multiple clients.

                 This  option  can  be  used  where  it  can   be
                 guaranteed  that  accesses  to  a specified file
                 system are made from only one  client  and  only
                 that  client. Under such a condition, the effect
                 of -nocto can be a slight performance gain.

                 The  server  IP  port  number.  The  default  is
                 NFS_PORT.  If  the port option is specified, and
                 if the resource includes one or more  NFS  URLs,
                 and  if  any  of the URLs include a port number,
                 then the port number in the option  and  in  the
                 URL must be the same.

           posix Request POSIX.1 semantics for the  file  system.
                 Requires  a  mount  Version  2 mountd(1M) on the
                 server. See standards(5) for information regard-
                 ing POSIX.

                 <netid> is a  value  of  network_id  field  from
                 entry  in  the  /etc/netconfig file. By default,
                 the transport protocol used for the NFS mount is
                 the  first  available  connection oriented tran-
                 sport supported  on  both  the  client  and  the
                 server.  If  no connection oriented transport is
                 found, then the first  available  connectionless
                 transport  is used. This default behavior can be
                 overridden with the proto=<netid> option.

                 The public option forces the use of  the  public
                 file  handle  when connecting to the NFS server.
                 The resource specified may or may  not  have  an
                 NFS  URL.  See  the  discussion of URL's and the
                 public option under NFS FILE SYSTEMS for a  more
                 detailed discussion.

           quota | noquota
                 Enable or prevent quota(1M) to check whether the
                 user  is  over quota on this file system; if the
                 file system has quotas enabled  on  the  server,
                 quotas  are still checked for operations on this
                 file system.

                 Remounts a read-only file system  as  read-write
                 (using  the  rw  option).  This option cannot be
                 used with other  -o  options,  and  this  option
                 works  only  on currently mounted read-only file

                 Set the number of NFS retransmissions to n.  The
                 default  value  is  5.  For  connection-oriented
                 transports, this option has no effect because it
                 is   assumed   that   the   transport   performs
                 retransmissions on behalf of NFS.

                 The number of times to retry  the  mount  opera-
                 tion.  The  default  for  the  mount  command is

                 The default for the automounter is 0,  in  other
                 words, do not retry. You might find it useful to
                 increase this value on heavily  loaded  servers,
                 where  automounter  traffic  is dropped, causing
                 unnecessary ``server not responding'' errors.

           ro | rw
                 resource is mounted read-only or read-write. The
                 default is rw.

                 Set the read buffer size to n bytes. The default
                 value  is  32768 when using Version 3 of the NFS
                 protocol. The default can be negotiated down  if
                 the server prefers a smaller transfer size. When
                 using Version 2, the default value is 8192.

                 Set the security mode for NFS  transactions.  If
                 sec=  is  not specified, then the default action
                 is to use AUTH_SYS over NFS Version 2 mounts, or
                 to  negotiate  a mode over NFS Version 3 mounts.
                 NFS Version 3 mounts negotiate a  security  mode
                 when  the  server  returns  an array of security
                 modes. The client picks the first  mode  in  the
                 array  that is supported on the client. Only one
                 mode can be specified with the sec= option.  See
                 nfssec(5) for the available mode options.

                 This option has been deprecated in favor of  the
                 sec=dh option.

           suid | nosuid
                 Allow or disallow setuid execution. The  default
                 is suid.

                 Set the NFS timeout to n tenths of a second. The
                 default  value is 11 tenths of a second for con-
                 nectionless transports,  and  600  tenths  of  a
                 second for connection-oriented transports.

           vers=<NFS version number>
                 By default, the version  of  NFS  protocol  used
                 between the client and the server is the highest
                 one available on both systems. If the NFS server
                 does  not  support  NFS Version 3 protocol, then
                 the NFS mount uses NFS Version 2 protocol.

                 Set the  write  buffer  size  to  n  bytes.  The
                 default  value  is 32768 when using Version 3 of
                 the NFS protocol. The default can be  negotiated
                 down  if  the  server prefers a smaller transfer
                 size. When using Version 2, the default value is

           xattr | noxattr
                 Allow or disallow the creation and  manipulation
                 of  extended  attributes.  The default is xattr.
                 See fsattr(5)  for  a  description  of  extended

     -O    Overlay mount. Allow the file  system  to  be  mounted
           over  an  existing  mount point, making the underlying
           file system inaccessible. If a mount is attempted on a
           pre-existing  mount  point  without setting this flag,
           the mount fails, producing the error "device busy."


     Background versus Foreground
           File systems mounted with the bg option indicate  that
           mount  is  to  retry in the background if the server's
           mount daemon  (mountd(1M))  does  not  respond.  mount
           retries  the  request up to the count specified in the
           retry=n option. (Note that the default value for retry
           differs  between mount and automount. See the descrip-
           tion  of  retry,  above.)  Once  the  file  system  is
           mounted,  each  NFS  request  made in the kernel waits
           timeo=n tenths of a second  for  a  response.   If  no
           response  arrives, the time-out is multiplied by 2 and
           the request  is  retransmitted.  When  the  number  of
           retransmissions  has  reached  the number specified in
           the retrans=n option, a file system mounted  with  the
           soft  option  returns  an  error  on  the request; one
           mounted with the hard option prints a warning  message
           and continues to retry the request.

     Hard versus Soft
           File systems that are mounted read-write or that  con-
           tain  executable  files  should always be mounted with
           the hard option. Applications using soft mounted  file
           systems  may incur unexpected I/O errors, file corrup-
           tion, and unexpected  program  core  dumps.  The  soft
           option is not recommended.

     Authenticated requests
           The server may require authenticated NFS requests from
           the  client.  sec=dh authentication might be required.
           See nfssec(5).

     URLs and the public option
           If the public option is specified, or if the  resource
           includes and NFS URL, mount attempts to connect to the
           server using the public file handle  lookup  protocol.
           See  WebNFS  Client  Specification,  RFC  2054. If the
           server supports the public file handle, the attempt is
           successful;   mount  does  not  need  to  contact  the
           server's rpcbind(1M), and the  mountd(1M)  daemons  to
           get  the  port number of the mount server and the ini-
           tial file handle of pathname, respectively. If the NFS
           client  and  server  are  separated by a firewall that
           allows  all  outbound  connections  through   specific
           ports,  such as NFS_PORT, then this enables NFS opera-
           tions through the firewall. The public option and  the
           NFS  URL  can  be specified independently or together.
           They interact as specified in the following matrix:

                                               resource style
                                 host:pathname         NFS URL
            public option        Force  public  file   Force  public   file
                                 handle   and   fail   handle    and   fail
                                 mount if  not  sup-   mount  if  not  sup-
                                 ported.               ported.
                                 Use Native paths.     Use Canonical paths.
            default              Use MOUNT protocol.   Try public file han-
                                                       dle  with  Canonical
                                                       paths. Fall back  to
                                                       MOUNT   protocol  if
                                                       not supported.

          |                    |                     |                     |
          |A Native path is  a |path  name  that  is |interpreted          |
          |according  to conventions used on the native operating          |
          |system of the NFS server. A Canonical path|is  a  path          |
          |name  that  is interpreted according to the URL rules.          |
          |See Uniform Resource|Locators  (URL),  RFC| 1738.  See          |
          |EXAMPLES for uses of|Native and Canonical paths.                |
          |                    |                     |                     |
     Replicated file systems and failover            |                     |
          |resource can list multiple read-only file |systems  to          |
          |be  used  to  provide  data. These file systems should          |
          |contain equivalent directory structures and  identical          |
          |files.  It is also recommended that they be created by          |
          |a utility such as rdist(1). The file  systems  may  be          |
          |specified   either  with  a  comma-separated  list  of          |
          |host:/pathname entries and/or NFS URL entries, or with          |
          |a  comma  -separated|list of hosts, if all|file system          |
          |names are the same. If multiple file systems are named          |
          |and  the  first  server  in the list is down, failover          |
          |uses the next alternate server to access files. If the          |
          |read-only  option  is  not chosen, replication is dis-          |
          |abled. File access is blocked on the original  if  NFS          |
          |locks are active for|that file.           |                     |
          |                    |                     |                     |
  File Attributes              |                     |                     |
     To improve NFS read performance, files and  file| attributes          |
     are  cached.  File modification times get updated whenever a          |
     write|occurs. However, file access times may be |temporarily          |
     out-of-date until the cache gets refreshed.     |                     |
          |                    |                     |                     |
     The attribute cache retains file attributes on  the  client.          |
     Attributes  for a file are|assigned a time to be|flushed. If          |
     the file is modified before the flush time, then| the  flush          |
     time |is  extended  by  the time since the last modification          |
     (under the assumption that files that changed  recently  are
     likely to change soon). There is a minimum and maximum flush
     time extension for regular files and for  directories.  Set-
     ting actimeo=n sets flush time to n seconds for both regular
     files and directories.

     Setting actimeo=0 disables attribute caching on the  client.
     This  means  that every reference to attributes is satisfied
     directly from the server though file data is  still  cached.
     While  this guarantees that the client always has the latest
     file attributes from the server, it has an adverse effect on
     performance  through  additional  latency, network load, and
     server load.

     Setting the noac option also disables attribute caching, but
     has  the  further  effect of disabling client write caching.
     While this guarantees that data written by an application is
     written directly to a server, where it can be viewed immedi-
     ately by other clients, it has a significant adverse  effect
     on client write performance. Data written into memory-mapped
     file pages  (mmap(2))  are  not  written  directly  to  this


     Example 1: Mounting an NFS File System

     To mount an NFS file system:

     example# mount serv:/usr/src /usr/src

     Example 2: Mounting An NFS File  System  Read-Only  With  No
     suid Privileges

     To  mount  an  NFS  file  system  read-only  with  no   suid

     example# mount -r -o nosuid serv:/usr/src /usr/src

     Example 3: Mounting An NFS File System Over Version 2,  with
     the UDP Transport

     To mount an NFS file system over Version  2,  with  the  UDP

     example# mount -o vers=2,proto=udp serv:/usr/src /usr/src

     Example 4: Mounting an NFS File System Using An NFS URL

     To mount an NFS file system using an NFS  URL  (a  canonical

     example# mount nfs://serv/usr/man /usr/man

     Example 5: Mounting An NFS File System Forcing  Use  Of  The
     Public File Handle

     To mount an NFS file system and force the use of the  public
     file handle and an NFS URL (a canonical path) that has a non
     7-bit ASCII escape sequence:

     example# mount -o public nfs://serv/usr/%A0abc /mnt/test

     Example 6: Mounting an NFS File System Using a Native Path

     To mount an NFS file system using a native path  (where  the
     server uses colons (":") as the component separator) and the
     public file handle:

     example# mount -o public serv:C:doc:new /usr/doc

     Example 7: Mounting a Replicated Set  of  NFS  File  Systems
     with the Same Pathnames

     To mount a replicated set of NFS file systems with the  same

     example# mount serv-a,serv-b,serv-c:/usr/man /usr/man

     Example 8: Mounting a Replicated Set  of  NFS  File  Systems
     with Different Pathnames

     To mount a replicated set of NFS file systems with different

     example# mount serv-x:/usr/man,serv-y:/var/man,nfs://serv-z/man /usr/man


           table of mounted file systems

           default distributed file system type

           table of automatically mounted resources


     See attributes(5) for descriptions of the  following  attri-

    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    | Availability                | SUNWnfscu                   |


     rdist(1),  mountall(1M),  mountd(1M),  quota(1M),  mkdir(2),
     mmap(2),  mount(2),  open(2),  umount(2),  mnttab(4), attri-
     butes(5),  fsattr(5),  nfssec(5),  standards(5),   inet(7P),
     inet6(7P), lofs(7FS)

     Callaghan, Brent, WebNFS  Client  Specification,  RFC  2054,
     October 1996.

     Callaghan, Brent, NFS URL Scheme, RFC 2224, October 1997.

     Berners-Lee, Masinter & McCahill , Uniform Resource Locators
     (URL), RFC 1738, December 1994.


     An NFS server should not attempt to mount its own file  sys-
     tems. See lofs(7FS).

     If the directory on which a file system is to be mounted  is
     a symbolic link, the file system is mounted on the directory
     to which the symbolic link refers, rather than being mounted
     on top of the symbolic link itself.

     SunOS 4.x used the biod  maintenance  procedure  to  perform
     parallel  read-ahead  and write-behind on NFS clients. SunOS
     5.x made biod obsolete with multi-threaded processing, which
     transparently performs parallel read-ahead and write-behind.

     Since the root (/) file system is mounted read-only  by  the
     kernel during the boot process, only the remount option (and
     options that can be used in conjunction with remount) affect
     the root (/) entry in the /etc/vfstab file.

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