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exports(4)

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NAME    [Toc]    [Back]

       exports  -  Defines  remote  mount  points  for  NFS mount
       requests

SYNOPSIS    [Toc]    [Back]

       /etc/exports

DESCRIPTION    [Toc]    [Back]

       The exports file specifies remote mount points for the NFS
       mount  protocol per the NFS server specification (see Network
 File System Protocol Specification, RFC1094).

       Each entry in the /etc/exports file consists of a filesystem
  or  directory  name  followed  by an optional list of
       options or an optional list of identifiers  or  both.  The
       identifiers  define which remote hosts can mount that particular
 filesystem or directory.

       The identifiers listed beside the name of each  filesystem
       or  directory  can  be either host names, IP addresses, or
       NIS netgroups names.  If no identifiers  are  listed,  the
       entry  is  exported  to all hosts.  If you are exporting a
       file system to a client that has multiple  network  interfaces
  on  a subnet, you must specify the host names or IP
       addresses for all of  the  interfaces;  otherwise,  export
       requests from the unspecified interfaces will be denied.

       A  backslash character (\) in the right-most position of a
       line indicates  line  continuation.   A  number  sign  (#)
       either  at the beginning of a line or at the end of a syntax
 line marks a comment that extends to the end  of  that
       line.   You  cannot use a number sign at the end of a line
       containing a backslash  character  because  the  backslash
       nullifies the end of line character.

       Note  that  the  mount command will touch the /etc/exports
       file when issued with the -t nfs option.  If you create  a
       new  /etc/exports  file, you should ensure that its ownership
 is equivalent to  that  of  the  default,  which  is;
       bin:bin (3:4).

       The format of the exports file is as follows:

       pathname [option ...] [identifier ...]

       #comments


       The  pathname  specifies  the  name  of  a  mounted  local
       filesystem or a directory of a mounted  local  filesystem.
       The pathname must begin in column 1.

       The  following  are valid export file options: Maps client
       superuser access to uid 0  for  all  hosts  mounting  this
       path.   If  you  want to allow client superusers access to
       the filesystem or directory with the same permissions as a
       local  superuser,  use  -root=0.   Use -root=0 only if you
       trust the superuser on the client system.  The default  is
       for client superusers to be mapped to uid -2, which maps a
       client superuser to nobody.  This limits access  to  world
       accessible  files.   If  both  the  -root=0 option and the
       -anon=uid option are used, the root option  overrides  the
       uid  specified  in  anon  for client superusers.  Maps the
       client superusers on the specified hosts only  to  uid  0.
       The format for the hostlist argument is as follows:

       client[:client]...

       The client specification can be a host name or IP address.
       By default, client superusers  are  mapped  to  -2.   This
       option overrides the uid specified in -anon=uid for client
       superusers in hostlist.  Maps anonymous users to the specified
  uid.  Client superusers are considered anonymous by
       the NFS server, as are requests that come in without  UNIX
       authentication.  By default, anonymous users are mapped to
       uid -2.  Setting anon to  -1  disables  anonymous  access.
       The filesystem or directory is exported read-only (default
       is read-write).  The -o option is a synonym  for  -ro  for
       backward  compatibility.   limits read-write access to the
       hosts specified.  All other hosts allowed  to  mount  this
       path  are  granted  read-only  access.  The format for the
       hostlist argument is as follows:

       client[:client]...

       The client specification can be a host name or IP address.
       If  both  the  -ro and -rw=hostlist options are specified,
       -rw prevails.  Exports a filesystem or directory for  WebNFS
 public access.  Note that only one exported filesystem
       can have this option set.

                                  Note
       When the -public option is set, the mount access  list  is
       ignored  by  the  WebNFS server. This means that all hosts
       using the WebNFS protocol have access to this directory.

       After setting the -public option,  be  sure  to  send  the
       mountd  process  a  HUP  signal.  See  kill(1) for further
       information.
       Used with -public option. Enables the server to  look  for
       an index.html file when given a directory name.  Specifies
       the hosts to grant mount access to.  The  format  for  the
       hostlist argument is as follows:

       client[:client]...

       The  client  specification can be a host name, IP address,
       or NIS network group.  This option is provided  for  readability
  and  compatibility  with certain export file formats.
  Alternatively, to identify the client  systems  who
       are allowed access to this export use the whitespace separated
 identifier list described below.

       The options can be applied to both file system and  directory
 entries in /etc/exports.

       Alternatively, you can list options using only one leading
       dash   and   separating   them   with   commas    as    in
       -option[,option]....

       You  use  the identifier field to specify host names, network
 groups, or both, separated by white space that  specify
  the  access  list  for  this  export.  Host names can
       optionally contain the local BIND domain name.  A  whitespace
  character  in the left-most position of a line indicates
 line continuation.

                                  Note
       If no hosts or netgroups are specified, the  mount  daemon
       exports this file system or directory to anyone requesting
       it.  See the mountd(8) reference page for  information  on
       how  to limit this scope to known hosts or to hosts in the
       same BIND domain.

       For example, suppose you enter:

       /usr -root=0  milan  kuan_yin.cis.berkeley.edu  /usr/local
       555.555.55.55  /u2  -ro /u3/dir1 -rw=milan:venice:florence
       /u3/dir2    -root=milan,access=venice:florence    /u3/dir3
       -root=0,access=milan:venice:florence    /u3/dir4   -root=0
       milan  venice  florence  /u3/dir5   -root=milan   -anon=-1
       /u3/dir6 -ro -public milan venice florence

       If  /usr,  /u2 and /u3 are local file system mount points,
       this specifies the following: /usr is exported  read-write
       to  hosts  milan  and  kuan_yin.cis.berkeley.edu with root
       mapped to uid=0.  /usr/local  is  exported  read-write  to
       host  555.555.55.55 with root mapped to -2.  (For security
       reasons, this  example  uses  the  fictitious  IP  address
       555.555.55.55.)   /u2  is  exported to all hosts read-only
       with root mapped to -2.  /u3/dir1 is  exported  read-write
       to  hosts milan, venice, and florence and read-only to all
       other hosts.   For  all  hosts,  root  is  mapped  to  -2.
       /u3/dir2  is exported with root mapped to 0 to host milan.
       Hosts milan, venice, and florence  are  allowed  to  mount
       this  directory read-write.  Root on hosts venice and florence
 is mapped to -2.  /u3/dir3  is  exported  read-write
       and with root mapped to 0 to hosts milan, venice, and florence.
  /u3/dir4 is exported in the  same  manner  as  the
       previous  example.  /u3/dir5 is exported read-write to all
       hosts.  Anonymous users are  not  allowed  to  mount  this
       directory,  with  the exception of the client superuser on
       host milan.  Root is mapped to 0 on host milan and  to  -2
       on  all  other  hosts.   /u3/dir6 Hosts milan, venice, and
       florence are allowed to mount  this  directory  read-only.
       All  other  hosts have read-only WebNFS access, but cannot
       mount this directory.

       Each file system that you want to allow clients  to  mount
       must  be  explicitly defined.  Exporting only the root (/)
       will not allow clients to mount /usr.  Exporting only /usr
       will  not  allow  clients  to mount /usr/local, if it is a
       file system.

       Duplicate directory entries are not  allowed.   The  first
       entry is valid and following duplicates are ignored.

       Desired  export  options  must be explicitly specified for
       each exported resource: file system or  directory.   If  a
       file system and subdirectories within it are exported, the
       options associated with the file system are  not  ``inherited.''
   You  do not need to export an entire file system
       to allow clients to mount subdirectories within it.

       The access list associated  with  each  exported  resource
       identifies  which clients can mount that resource with the
       specified options.  For example, you can export an  entire
       file  system  read-only,  with  a  subdirectory  within it
       exported read-write to a subset of clients.  If  a  client
       that  is  not  identified  in  the export access list of a
       directory attempts to mount it,  then  access  is  checked
       against the closest exported ancestor.  If mount access is
       allowed at a higher level in the  directory  tree  of  the
       file  system,  the  export  options  associated  with  the
       successful match will be in effect.

       To make a change to the exports  file  and  have  it  take
       effect  immediately, send the mountd process a HUP signal.
       Otherwise, the mountd process will reread the exports file
       the  next  time  it  receives  a mount request from an NFS
       client or a showmount -e request.

RELATED INFORMATION    [Toc]    [Back]

       Daemons: mountd(8), nfsd(8)

       Commands: showmount(8)

       Files: hosts(4), netgroup(4)

       Network Administration: Services delim off



                                                       exports(4)
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