Manual Pages for UNIX Darwin command on man exports

EXPORTS(5) BSD File Formats Manual EXPORTS(5)

NAME

eexxppoorrttss - define remote mount points for NFS mount requests

SYNOPSIS

eexxppoorrttss

DESCRIPTION

The eexxppoorrttss file specifies remote mount points for the NFS mount protocol per the NFS server specification; see Network File System Protocol Specification RFC 1094, Appendix A and NFS: Network File System Version 3 Specification, Appendix I. Fields are separated by space or tab characters. Lines that begin with a

# are considered comments and are ignored.

Each line in the file specifies one or more exported directories, any

additional mountable sub-directories within those directories, export

flags, and one or more hosts (if access to the export is to be restricted). All directories on the line must exist within the same local file system.

Within a file system there may be several exported sub-directories with

different export options. However, none of those exported directories may lie within another. A host may be specified only once for each exported directory and there may be only one default entry for each exported directory that applies to

all other hosts. The latter exports the file system to the ``world'' and

should be used only when the file system contains public information. Any attempt to export the same directory to a host with different export options will cause the conflicting export entry to be rejected. The first field(s) of an export entry is a list of directories on a local file system to export. At least one pathname must be to an exported

directory. Other pathnames may refer to sub-directories of the exported

directory to indicate that hosts are also allowed to explicitly mount

those sub-directories of the exported directory. (Note that the -aallllddiirrss

flag can be used to allow mounting any sub-directories of the pathnames

specified.) Mount points for a file system may appear on multiple lines, each with different sets of hosts and export options. The pathnames must not have any symbolic links in them and should not have any "." or ".." components. Single and double quote characters occuring in a pathname must be escaped with \' and \", respectively.

Space characters occuring in a pathname must be escaped, or alterna-

tively, the pathname can be enclosed in single or double quotes. Note that because an export entry only lists a set of pathnames, it is up to the NFS server to correctly determine what file system is meant to be

exported by that entry. To that end, the server will attempt to intelli-

gently decide which file system best matches the entry by comparing all the pathnames with both the current list of mounted file systems and the

list of previously-exported file systems. If the server determines that

the intended file system is not available, it will automatically mark that export as offline until the file system becomes available (see the

-oofffflliinnee export option below for more info). To avoid any ambiguity, use

of the -ffss export option is recommended (see below).

The second component of a line specifies how the file system is to be

exported to the host set. The option flags specify whether the file sys-

tem is exported read-only or read-write and how the client uid is mapped

to user credentials on the server. Export options are specified as follows:

-mmaapprroooott=uusseerr The credential of the specified user is used for remote

access by root. The credential includes all the groups to which the user is a member on the local machine ( see id(1) ). The user may be specified by name or number.

-mmaapprroooott=uusseerr::ggrroouupp11::ggrroouupp22::...... The colon separated list is used to spec-

ify the precise credential to be used for remote access by root. The elements of the list may be either names or numbers. Note that ``user:'' should be used to distinguish a credential containing no groups from a complete credential for that user.

-mmaappaallll=uusseerr or -mmaappaallll=uusseerr::ggrroouupp11::ggrroouupp22::...... specifies a mapping for

all client uids (including root) using the same semantics as -mmaapprroooott.

The option -rr is a synonym for -mmaapprroooott in an effort to be backward com-

patible with older export file formats.

In the absence of -mmaapprroooott and -mmaappaallll options, remote accesses by root

will result in using a credential of -2:-2. All other users will be

mapped to their remote credential. If a -mmaapprroooott option is given, remote

access by root will be mapped to that credential instead of -2:-2. If a

-mmaappaallll option is given, all users (including root) will be mapped to

that credential in place of their own.

The -aallllddiirrss flag allows the host(s) to mount at any point within the

file system, including regular files if the -RR option is used on nfsd.

The -rroo option specifies that the file system should be exported read-

only (default read/write). The option -oo is a synonym for -rroo in an

effort to be backward compatible with older export file formats.

The -3322bbiittcclliieennttss option causes the NFS server to guarantee that direc-

tory cookies will fit within 32 bits even though directory cookies are 64 bits in NFSv3. This option may be required with NFS clients that do not properly support 64 bit directory cookies. Use of this option may result

in sub-optimal performance of the exported file system.

-sseecc=mmeecchhaanniissmm11::mmeecchhaanniissmm22...... This option specifies one or more security

mechanisms required for access to the exported directory. The security mechanisms currently supported are krb5p, krb5i, krb5, and sys. Multiple security mechanisms can be specified as a colon separated list, and should be in the order of most preferred to least preferred. In the absence of this option, the security mechanism defaults to sys.

-oofffflliinnee This option specifies that the given export should be treated as

if the exported file system is not available. For NFSv3, this will cause clients to receive "jukebox" errors directing them to try the request later. For NFSv2 (which does not support this error value), the export

will be treated as non-existent and clients will receive stale file han-

dle errors.

-ffssppaatthh=//ppaatthh and/or -ffssuuuuiidd=UUUUIIDD These options can be used to specify

the pathname to and/or the UUID of the file system that is intended to be exported. This can be useful to disambiguate the export entry. Since the export syntax only specifies the path to the directory to be exported, it can be ambiguous as to what file system is expected to be exported. Specifying "/Volumes/XRAID" can be interpreted as exporting either a file system mounted on that directory or the "Volumes/XRAID"

subdirectory of the root file system. Specifying -ffssppaatthh=//VVoolluummeess//XXRRAAIIDD

can prevent exporting the wrong file system - for example, if the exports

are evaluated at a point when the directory exists but the volume has not yet been mounted on it. The export will fail if the file system referred to in an export entry either (1) is not mounted at the same path as the

given -ffssppaatthh=//ppaatthh. or (2) does not have a UUID that matches the given

-ffssuuuuiidd=UUUUIIDD.

The third component of a line specifies the host set to which the line applies. The set may be specified in three ways. The first way is to list the host name(s) separated by white space. (Standard internet ``dot'' addresses may be used in place of names.) The second way is to specify a ``netgroup'' as defined in the netgroup file (see netgroup(5)

). The third way is to specify an internet sub-network using a network

and network mask that is defined as the set of all hosts with addresses

within the sub-network. This latter approach requires less overhead

within the kernel and is recommended for cases where the export line

refers to a large number of clients within an administrative sub-net.

The first two cases are specified by simply listing the name(s) separated by whitespace. All names are checked to see if they are ``netgroup'' names first and are assumed to be hostnames otherwise. Using the full domain specification for a hostname can normally circumvent the problem

of a host that has the same name as a netgroup. The third case is speci-

fied by the flag -nneettwwoorrkk=nneettnnaammee and optionally -mmaasskk=nneettmmaasskk. If the

mask is not specified, it will default to the mask for that network class (A, B or C; see inet(5) ). EEXXAAMMPPLLEESS

/usr /usr/local -maproot=0:10 friends

/usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16

/usr -ro -mapall=nobody

/u -maproot=bin: -network 131.104.48 -mask 255.255.255.0

/u2 -maproot=root friends

/u2 -alldirs -network cis-net -mask cis-mask

/Users -alldirs -network 2.29.96.0 -mask 255.255.255.0

/Applications -ro -network 2.29.96.0 -mask 255.255.255.0

Given that /usr, /u, /u2, and / are local file system mount points, the above example specifies the following:

/usr is exported to hosts friends, where friends is specified in the net-

group file with users mapped to their remote credentials and root mapped

to uid 0 and group 10. It is exported read-write and the hosts in

friends can mount either /usr or /usr/local. It is exported to 131.104.48.16 and grumpy.cis.uoguelph.ca with users mapped to their remote credentials and root mapped to the user and groups associated with

``daemon''; it is exported to the rest of the world as read-only with all

users mapped to the user and groups associated with ``nobody''.

/u is exported to all hosts on the sub-network 131.104.48 with root

mapped to the uid for ``bin'' and with no group access. /u2 is exported to the hosts in ``friends'' with root mapped to uid and groups associated with ``root''; it is exported to all hosts on network

``cis-net'' allowing mounts at any directory within /u2.

The /Users and /Applications sub-directories of / are exported to all

hosts on the sub-network 2.29.96. Any directory within /Users can be

mounted. /Users is exported read-write and /Applications is exported

read-only.

FILES

/etc/exports The default remote mount-point file.

BUGS

It is recommended that all exported directories within the same server

file system be specified on adjacent lines going down the tree. You can-

not specify a hostname that is also the name of a netgroup. Specifying the full domain specification for a hostname can normally circumvent the problem. BSD October 25, 2006 BSD