


NFS(5)		Linux Programmer's Manual		NFS(5)


NNAAMMEE
       nfs - nfs fstab format and options

SSYYNNOOPPSSIISS
       //eettcc//ffssttaabb

DDEESSCCRRIIPPTTIIOONN
       The  _f_s_t_a_b  file contains information about which filesys-
       tems to mount  where  and  with	what  options.	For  NFS
       mounts,	it  contains  the server name and exported server
       directory to mount from, the local directory that  is  the
       mount point, and the NFS specific options that control the
       way the filesystem is mounted.

       Here is an example from an _/_e_t_c_/_f_s_t_a_b  file  from  an  NFS
       mount.

       server:/usr/local/pub	/pub   nfs    timeo=14,intr

   OOppttiioonnss
       _r_s_i_z_e_=_n	The  number  of bytes NFS uses when reading
		      files from  an  NFS  server.   The  default
		      value is dependent on the kernel, currently
		      1024 bytes.

       _w_s_i_z_e_=_n	The number of bytes NFS uses  when  writing
		      files  to an NFS server.	The default value
		      is dependent on the kernel, currently  1024
		      bytes.

       _t_i_m_e_o_=_n	The  value  in  tenths  of  a second before
		      sending the first retransmission	after  an
		      RPC timeout.  The default value is 7 tenths
		      of a second.  After the first timeout,  the
		      timeout  is  doubled  after each successive
		      timeout until a maximum timeout of 60  sec-
		      onds  is	reached or the enough retransmis-
		      sions have occured to cause a  major  time-
		      out.   Then,  if	the  filesystem	is  hard
		      mounted, each new timeout cascade	restarts
		      at  twice the initial value of the previous
		      cascade, again doubling at each retransmis-
		      sion.   The  maximum  timeout  is always 60
		      seconds.	Better overall performance may be
		      achieved	by  increasing	the  timeout when
		      mounting on  a  busy  network,  to  a  slow
		      server, or through several routers or gate-
		      ways.

       _r_e_t_r_a_n_s_=_n      The number of minor timeouts  and	retrans-
		      missions	that  must  occur  before a major
		      timeout occurs.  The default is 3 timeouts.
		      When a major timeout occurs, the file oper-
		      ation is either aborted or  a  "server  not



			 11 January 1993			1





NFS(5)		Linux Programmer's Manual		NFS(5)


		      responding"  message is printed on the con-
		      sole.

       _a_c_r_e_g_m_i_n_=_n     The minimum time in seconds that attributes
		      of  a  regular file should be cached before
		      requesting fresh information from a server.
		      The default is 3 seconds.

       _a_c_r_e_g_m_a_x_=_n     The maximum time in seconds that attributes
		      of a regular  file  can  be  cached  before
		      requesting fresh information from a server.
		      The default is 60 seconds.

       _a_c_d_i_r_m_i_n_=_n     The minimum time in seconds that attributes
		      of  a  directory	should	be  cached before
		      requesting fresh information from a server.
		      The default is 30 seconds.

       _a_c_d_i_r_m_a_x_=_n     The maximum time in seconds that attributes
		      of  a  directory	can  be	cached   before
		      requesting fresh information from a server.
		      The default is 60 seconds.

       _a_c_t_i_m_e_o_=_n      Using actimeo sets all of _a_c_r_e_g_m_i_n_,  _a_c_r_e_g_-
		      _m_a_x_,  _a_c_d_i_r_m_i_n_,  and  _a_c_d_i_r_m_a_x  to the same
		      value.  There is no default value.

       _p_o_r_t_=_n	 The numeric value of the UDP port	to  con-
		      nect  to the NFS server on.  The default is
		      the standard NFS port number 2049.

       _r_e_t_r_y_=_n	The number of times to retry a backgrounded
		      NFS  mount operation before giving up.  The
		      default value is 10000 times.

       _b_g	     If the first NFS mount attempt  times  out,
		      continue	trying	the  mount  in	the back-
		      ground.  The default is  to  not	to  back-
		      ground the mount on timeout but fail.

       _f_g	     If  the  first NFS mount attempt times out,
		      fail immediately.	This is the default.

       _s_o_f_t	   If an NFS file operation has a major  time-
		      out  then	report an IO to the calling pro-
		      gram.  The default is to continue	retrying
		      NFS file operations indefinitely.

       _h_a_r_d	   If  an NFS file operation has a major time-
		      out then report "server not responding"  on
		      the  console  and continue retrying indefi-
		      nitely.  This is the default.

       _i_n_t_r	   If  an  NFS  file	operation  has	a  major



			 11 January 1993			2





NFS(5)		Linux Programmer's Manual		NFS(5)


		      timeout  and it is hard mounted, then allow
		      signals to interupt the file operation  and
		      cause  it	to  return  EINTR to the calling
		      program.	The default is to not allow  file
		      operations to be interrupted.

       _p_o_s_i_x	  Mount the NFS filesystem using POSIX seman-
		      tics.

       _n_o_c_t_o	  Supress the  retrieval  of  new  attributes
		      when creating a file.

       _n_o_a_c	   Disable  all  forms  of  attribute  caching
		      entirely.	This extracts a  server  perfor-
		      mance  penalty  but it allows two different
		      NFS clients to get reasonable good  results
		      when  both  clients are actively writing to
		      common filesystem on the server.

       All of the non-value options have  corresponding	nooption
       forms.	For example, nointr means don't allow file opera-
       tions to be interrupted.

FFIILLEESS
       /etc/fstab

SSEEEE AALLSSOO
       fstab(5), mount(8), umount(8)

AAUUTTHHOORR
       "Rick Sladkey" <jrs@world.std.com>

BBUUGGSS
       The bg, fg retry, posix, and nocto options are  parsed  by
       mount but currently are silently ignored.

       The  umount  command  should notify the server when an NFS
       filesystem is unmounted.



















			 11 January 1993			3


