ChorusOS man pages section 4CC: Files

exports(4CC)

NAME

exports- define remote mount points for NFS mount requests

SYNOPSIS

/etc/exports

FEATURES

NFS_SERVER

DESCRIPTION

The exports file specifies remote mount points for the NFS mount protocol as defined in the NFS server specification; see "Network File System Protocol Specification RFC 1094, Appendix A" .

Each line in the file (other than comment lines that begin with a #) specifies the mount point(s) and export flags within one local server filesystem for one or more hosts. A host may be specified only once for each local filesystem on the server and there may be only one default entry for each server filesystem that applies to all other hosts. The latter exports the filesystem to the ``world'' and should be used only when the filesystem contains public information.

In a mount entry, the first field(s) specifies the directory path(s) within a server filesystem that can be mounted onto by the corresponding client(s). There are two forms of this specification. The first is to list all mount points as absolute directory paths separated by whitespace. The second is to specify the pathname of the root of the filesystem followed by the -alldirs flag; this form allows the host(s) to mount any directory within the filesystem. The pathnames must not have any symbolic links in them and should not have any "." or ".." components. Mount points for a filesystem may appear on multiple lines, each with different sets of hosts and export options.

The second component of a line specifies how the filesystem is to be exported to the host set. The option flags specify whether the filesystem 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:

-maproot=<uid>

The credential of the specified user is used for remote access by root. The credential includes all the groups of which the user is a member on the local machine. The user may be specified by name or number. On top of ChorusOS numbers only are supported, Neither /etc/passwd or /etc/groups are supported.

-maproot=<uid>:<gid0>:<gid1>:<gid2>

The colon (":") separated list is used to specify the precise credentials to be used for remote access by root. The elements of the list may be either names or numbers. On top of ChorusOS names are not supported, only numbers. Note that "user:" should be used to distinguish a credential containing no groups from a complete credential for that user.

-mapall=<uid> or -mapall=<uid>:<gid0>:<gid1>:<gid2>

specifies a mapping for all client uids (including root) using the same semantics as maproot.

The option -r is a synonym for maproot in order to be backward compatible with older export file formats.

In the absence of the maproot and mapall 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 maproot option is given, remote access by root will be mapped to that credential instead of -2:-2. If a mapall option is given, all users (including root) will be mapped to that credential instead of their own.

The kerb option specifies that the Kerberos authentication server should be used to authenticate and map client credentials.

The -ro option specifies that the filesystem should be exported read-only (default read/write). The option -o is a synonym for -ro in order to be backward compatible with older export file formats.

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 instead of names.) The second way is to specify a ``netgroup'' as defined in the netgroup file (see netgroup). The third way is to specify an internet subnetwork using a network and network mask that is defined as the set of all hosts with addresses within the subnetwork. 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 subnet.

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 usually circumvent the problem of a host that has the same name as a netgroup. The third case is specified by the flag -network=<netname> and, optionally, -mask=<netmask>. If the mask is not specified, it will default to the mask for that network class (A, B or C; see inet(7P)).

This third component specifying host(s) and netgroup is not yet supported on top of ChorusOS.

For example:

/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 -kerb -network cis-net -mask
/mnt0 -alldirs -maproot=0:1

Given that /usr , /u and /u2 are local filesystem mount points, the above example specifies the following: /usr is exported to host friends, where friends is specified in the netgroup file with users mapped to their remote credentials, and root is 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''.

The /u mount point is exported to all hosts on the subnetwork 131.104.48 with the root mapped to the uid for ``bin'', and with no group access.

The /u2 mount point is exported to the host in ``friends'' with the root mapped to uid and groups associated with ``root''. It is exported to all hosts on the network ``cis-net'', allowing mounts at any directory within /u2, and mapping all uids to credentials for the principal that is authenticated by a Kerberos ticket.

The /mnt0 mount point is exported for everyone and root credentials are mapped to uid=0 and gid=1. All other users are mapped to their own credentials. This configuration is typically used with ChorusOS.

FILES

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

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Evolving

BUGS

The export options are tied to the local mount points in the kernel and must be non-contradictory for any exported subdirectory of the local server mount point. It is recommended that all exported directories within the same server filesystem be specified on adjacent lines going down the tree. You cannot specify a hostname that is also the name of a netgroup. Specifying the full domain specification for a hostname can usually circumvent this problem.

ChorusOS 4.0 Last Revised December 1999