mount Options for NFS File Systems

The subsequent text lists some of the options that can follow the -o flag when mounting an NFS file system.

bg|fg

These options can be used to select the retry behavior if a mount fails. The -bg option causes the mount attempts to be run in the background. The -fg option causes the mount attempt to be run in the foreground. The default is -fg, which is the best selection for file systems that must be available. It prevents further processing until the mount is complete. -bg is a good selection for file systems that are not critical, because the client can do other processing while waiting for the mount request to complete.

forcedirectio

This option improves performance of sequential reads on large files. Data is copied directly to a user buffer and no caching is done in the kernel on the client. This option is off by default.

largefiles

This option makes it possible to access files larger than 2 Gbytes on a server running the Solaris 2.6 release. Whether a large file can be accessed can only be controlled on the server, so this option is silently ignored on NFS version 3 mounts. Starting with release 2.6, by default, all UFS file systems are mounted with -largefiles. For mounts using the NFS version 2 protocol, the -largefiles option causes the mount to fail with an error.

nolargefiles

This option for UFS mounts guarantees that there are and will be no large files on the file system (see the mount_ufs(1M) man page). Because the existence of large files can only be controlled on the NFS server, there is no option for -nolargefiles using NFS mounts. Attempts to NFS mount a file system using this option are rejected with an error.

public

This option forces the use of the public file handle when contacting the NFS server. If the public file handle is supported by the server, the mounting operation is faster because the MOUNT protocol is not used. Also, because the MOUNT protocol is not used, the public option allows mounting to occur through a firewall.

rw|ro

The -rw and -ro options indicate whether a file system is to be mounted read-write or read-only. The default is read-write, which is the appropriate option for remote home directories, mail-spooling directories, or other file systems that need to be changed by users. The read-only option is appropriate for directories that should not be changed by users; for example, shared copies of the man pages should not be writable by users.

sec=mode

You can use this option to specify the authentication mechanism to be used during the mount transaction. The value for mode can be one of the values shown in Table 31-2. The modes are also defined in /etc/nfssec.conf.

Table 31-2 NFS Security Modes

Mode	Authentication Service Selected
krb5	Kerberos Version 5
none	No authentication
dh	Diffie-Hellman (DH) authentication
sys	Standard UNIX authentication

soft|hard

An NFS file system mounted with the soft option returns an error if the server does not respond. The hard option causes the mount to continue to retry until the server responds. The default is hard, which should be used for most file systems. Applications frequently do not check return values from soft-mounted file systems, which can make the application fail or can lead to corrupted files. Even if the application does check, routing problems and other conditions can still confuse the application or lead to file corruption if the soft option is used. In most cases the soft option should not be used. If a file system is mounted using the hard option and becomes unavailable, an application using this file system will hang until the file system becomes available.