Features of the NFS Service

This section covers the important features that are included in the NFS service.

NFS Version 2 Protocol

Version 2 was the first version of the NFS protocol in wide use. Version 2 continues to be available on a large variety of platforms. All Solaris releases support version 2 of the NFS protocol, but Solaris releases prior to Solaris 2.5 support version 2 only.

NFS Version 3 Protocol

An implementation of NFS version 3 protocol was a new feature of the Solaris 2.5 release. Several changes have been made to improve interoperability and performance. For optimal use, the version 3 protocol must be running on both the NFS servers and clients.

This version enables safe asynchronous writes on the server, which improve performance by allowing the server to cache client write requests in memory. The client does not need to wait for the server to commit the changes to disk, so the response time is faster. Also, the server can batch the requests, which improves the response time on the server.

All Solaris NFS version 3 operations return the file attributes, which are stored in the local cache. Because the cache is updated more often, the need to do a separate operation to update this data arises less often. Therefore, the number of RPC calls to the server is reduced, improving performance.

The process for verifying file access permissions has been improved. Specifically, version 2 generated a message that reported a “write error” or a “read error” if users tried to copy a remote file to which they did not have permissions. In version 3, the permissions are checked before the file is opened, so the error is reported as an “open error.”

The NFS version 3 protocol removes the 8-Kbyte transfer size limit. Clients and servers negotiate whatever transfer size they support, rather than conform to the 8-Kbyte limit imposed in version 2. The Solaris 2.5 implementation defaults to a 32-Kbyte transfer size.

NFS ACL Support

Access control list (ACL) support was added in the Solaris 2.5 release. ACLs provide a finer-grained mechanism to set file access permissions than is available through standard UNIX file permissions. NFS ACL support provides a method of changing and viewing ACL entries from a Solaris NFS client to a Solaris NFS server. See “Using Access Control Lists (ACLs)” in System Administration Guide: Security Services for more information about ACLs.

NFS Over TCP

The default transport protocol for the NFS protocol was changed to the Transport Control Protocol (TCP) in the Solaris 2.5 release. TCP helps performance on slow networks and wide area networks. TCP also provides congestion control and error recovery. NFS over TCP works with version 2 and version 3. Prior to 2.5, the default NFS protocol was User Datagram Protocol (UDP).

Network Lock Manager and NFS

The Solaris 2.5 release also included an improved version of the network lock manager, which provided UNIX record locking and PC file sharing for NFS files. The locking mechanism is now more reliable for NFS files, so commands which use locking are less likely to hang.

NFS Large File Support

The Solaris 2.6 implementation of the NFS version 3 protocol was changed to correctly manipulate files larger than 2 Gbytes. The NFS version 2 protocol and the Solaris 2.5 implementation of the version 3 protocol cannot handle files larger than 2 Gbytes.

NFS Client Failover

Dynamic failover of read-only file systems was added in the Solaris 2.6 release. Failover provides a high level of availability for read-only resources that are already replicated, such as man pages, other documentation, and shared binaries. Failover can occur anytime after the file system is mounted. Manual mounts can now list multiple replicas, much like the automounter in previous releases. The automounter has not changed, except that failover need not wait until the file system is remounted. See How to Use Client-Side Failover and Client-Side Failover for more information.

Kerberos Support for the NFS Service

Support for Kerberos V4 clients was included in the Solaris 2.0 release. In the 2.6 release, the mount and share commands were altered to support NFS version 3 mounts that use Kerberos V5 authentication. Also, the share command was changed to enable multiple authentication flavors for different clients. See RPCSEC_GSS Security Flavor for more information about changes that involve security flavors. See “Configuring SEAM NFS Servers” in System Administration Guide: Security Services for information about Kerberos V5 authentication.

WebNFS Support

The Solaris 2.6 release also included the ability to make a file system on the Internet accessible through firewalls, using an extension to the NFS protocol. One of the advantages to using the WebNFS^TM protocol for Internet access is its reliability. The service is built as an extension of the NFS version 3 and version 2 protocol. Also, an NFS server provides greater throughput under a heavy load than Hypertext Transfer protocol (HTTP) access to a Web server. This throughput can decrease the amount of time that is required to retrieve a file. In addition, the WebNFS implementation provides the ability to share these files without the administrative overhead of an anonymous ftp site. See Security Negotiation for the WebNFS Service for a description of more changes that are related to the WebNFS service. See WebNFS Administration Tasks for more task information.

RPCSEC_GSS Security Flavor

A security flavor, called RPCSEC_GSS, is supported in the Solaris 7 release. This flavor uses the standard GSS-API interfaces to provide authentication, integrity, and privacy, as well as enabling support of multiple security mechanisms. See Kerberos Support for the NFS Service for more information about support of Kerberos V5 authentication. See GSS-API Programming Guide for more information about GSS-API.

Solaris 7 Extensions for NFS Mounting

The Solaris 7 release includes extensions to the mount command and automountd command that enable the mount request to use the public file handle instead of the MOUNT protocol. The MOUNT protocol is the same access method that the WebNFS service uses. By circumventing the MOUNT protocol, the mount can occur through a firewall. In addition, because fewer transactions need to occur between the server and client, the mount should occur faster.

The extensions also enable NFS URLs to be used instead of the standard path name. Also, you can use the public option with the mount command and the automounter maps to force the use of the public file handle. See WebNFS Support for more information about changes to the WebNFS service.

Security Negotiation for the WebNFS Service

A new protocol has been added to enable a WebNFS client to negotiate a security mechanism with an NFS server in the Solaris 8 release. This protocol provides the ability to use secure transactions when using the WebNFS service. See How WebNFS Security Negotiation Works for more information.

NFS Server Logging

In the Solaris 8 release, NFS server logging enables an NFS server to provide a record of file operations that have been performed on its file systems. The record includes information to track what is accessed, when it is accessed, and who accessed it. You can specify the location of the logs that contain this information through a set of configuration options. You can also use these options to select the operations that should be logged. This feature is particularly useful for sites that make anonymous FTP archives available to NFS and WebNFS clients. See How to Enable NFS Server Logging for more information.

Autofs Features

Autofs works with file systems that are specified in the local name space. This information can be maintained in NIS, NIS+, or local files.

A fully multithreaded version of automountd was included in the Solaris 2.6 release. This enhancement makes autofs more reliable and enables concurrent servicing of multiple mounts, which prevents the service from hanging if a server is unavailable.

The new automountd also provides better on-demand mounting. Previous releases would mount an entire set of file systems if they were hierarchically related. Now only the top file system is mounted. Other file systems that are related to this mount point are mounted when needed.

The autofs service supports browsability of indirect maps. This support enables a user to see what directories could be mounted, without having to actually mount each one of the file systems. A -nobrowse option has been added to the autofs maps, so that large file systems, such as /net and /home, are not automatically browsable. Also, you can turn off autofs browsability on each client by using the -n option with automount. See Disabling Autofs Browsability for more information.