NAME

mount_nfs − mount remote NFS resources

SYNOPSIS

mount [ −F nfs ] [ −r ] [ −m ] [ −o specific_options ] [ resource mountpoint ]

DESCRIPTION

mount attaches a named resource to the file system hierarchy at the pathname location mountpoint, which must already exist. If mountpoint has any contents prior to the mount operation, the contents remain hidden until the resource is once again unmounted. 

If the resource is listed in the vfstab file, the command line can specify either resource or mountpoint, and mount will consult vfstab for more information.  If the −F option is omitted, mount takes the file system type from vfstab. 

mount maintains a table of mounted file systems in /etc/mnttab, described in mnttab(4). 

OPTIONS

−r Mount the specified file system read-only. 

−m Do not append an entry to the /etc/mnttab table of mounted file systems

−o specific_options
Specify file system specific options in a comma-separated list of words from the list below.

rw|ro resource is mounted read-write or read-only.  The default is rw. 

suid|nosuid Setuid execution allowed or disallowed.  The default is suid. 

remount If a file system is mounted read-only, remounts the file system read-write. 

bg|fg If the first attempt fails, retry in the background, or, in the foreground.  The default is fg. 

retry=n The number of times to retry the mount operation.  The default is 10000. 

port=n The server IP port number.  The default is NFS_PORT. 

grpid Create a file with its GID set to the effective GID of the calling process.  This behavior may be overridden on a per-directory basis by setting the set-GID bit of the parent directory; in this case, the GID is set to the GID of the parent directory (see open(2) and mkdir(2)).  Files created on file systems that are not mounted with the grpid option will obey BSD semantics; that is, the GID is unconditionally inherited from that of the parent directory. 

rsize=n Set the read buffer size to n bytes. 

wsize=n Set the write buffer size to n bytes. 

timeo= Set the NFS timeout to n tenths of a second. 

retrans=n Set the number of NFS retransmissions to n.

soft|hard Return an error if the server does not respond, or continue the retry request until the server responds. 

intr|nointr Allow (do not allow) keyboard interrupts to kill a process that is hung while waiting for a response on a hard-mounted file system.  The default is intr. 

secure Use DES authentication for NFS transactions. 

posix Request POSIX.1 semantics for the file system.  Requires a mount version 2 mountd(1M) on the server. 

kerberos Use Kerberos authentication for NFS transactions. 

noac Suppress attribute caching. 

acregmin=n Hold cached attributes for at least n seconds after file modification. 

acregmax=n Hold cached attributes for no more than n seconds after file modification. 

acdirmin=n Hold cached attributes for at least n seconds after directory update. 

acdirmax=n Hold cached attributes for no more than n seconds after directory update. 

actimeo=n Set min and max times for regular files and directories to n seconds. 

NFS FILE SYSTEMS

Background vs. Foreground
File systems mounted with the bg option indicate that mount is to retry in the background if the server’s mount daemon ( mountd(1M)) does not respond.  mount retries the request up to the count specified in the retry=n option.  Once the file system is mounted, each NFS request made in the kernel waits timeo=n tenths of a second for a response.  If no response arrives, the time-out is multiplied by 2 and the request is retransmitted.  When the number of retransmissions has reached the number specified in the retrans=n option, a file system mounted with the soft option returns an error on the request; one mounted with the hard option prints a warning message and continues to retry the request. 

Hard vs. Soft
File systems that are mounted read-write or that contain executable files should always be mounted with the hard option.  Applications using soft mounted filesystems may incur unexpected I/O errors. 

Authenticated Requests
The server may require authenticated NFS requests from the client. Either secure or kerberos authentication may be required. 

File Attributes

The attribute cache retains file attributes on the client.  Attributes for a file are assigned a time to be flushed.  If the file is modified before the flush time, then the flush time is extended by the time since the last modification (under the assumption that files that changed recently are likely to change soon).  There is a minimum and maximum flush time extension for regular files and for directories.  Setting actimeo=n extends flush time by n seconds for both regular files and directories. 

EXAMPLES

To mount an NFS file system:

example# mount serv:/usr/src /usr/src

To mount an NFS file system readonly with no suid privileges:

example# mount −r −o nosuid serv:/usr/src /usr/src

FILES

/etc/mnttab table of mounted file systems

/etc/dfs/fstypes default distributed file system type

/etc/vfstab table of automatically mounted resources

SEE ALSO

mountall(1M), mountd(1M), mount(2), umount(2), mnttab(4)

NOTES

If the directory on which a file system is to be mounted is a symbolic link, the file system is mounted on the directory to which the symbolic link refers, rather than being mounted on top of the symbolic link itself. 

SunOS 5.1  —  Last change: 11 Aug 1992