mount_nfs(1M) Maintenance Commands mount_nfs(1M) NAME mount_nfs - mount remote NFS resources SYNOPSIS mount [ -F nfs ] [ -r ] [ -m ] [ -o specific_options ] [ -O ] resource | mount_point DESCRIPTION mount attaches a named resource to the file system hierarchy at the pathname location mount_point, which must already exist. If mount_point 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 mount_point, 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 Set file system specific options according to a comma- separated list chosen from words 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 By default, the GID associated with a neewly created file will obey the System V semantics; that is, the GID is set to the effective GID of the calling pro- cess. 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 of a newly created file is set to the GID of the parent directory (see open(2) and mkdir(2)). Files created on file systems that are mounted with the grpid option will obey BSD semantics independent of whether the set-GID bit of the parent directory is set; that is, the GID is unconditionally inherited from that of the parent direc- tory. rsize=n Set the read buffer size to n bytes. The default value is 8192. wsize=n Set the write buffer size to n bytes. The default value is 8192. timeo=n Set the NFS timeout to n tenths of a second. The default value is 11. retrans=n Set the number of NFS retransmissions to n. The default value is 5. soft|hard Return an error if the server does not respond, or continue the retry request until the server responds. The default value is hard. 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 transac- tions. 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. The default value is 3. acregmax=n Hold cached attributes for no more than n seconds after file modification. The default value is 60. acdirmin=n Hold cached attributes for at least n seconds after directory update. The default value is 30. acdirmax=n Hold cached attributes for no more than n seconds after directory update. The default value is 60. actimeo=n Set min and max times for regular files and directories to n seconds. -O Overlay mount. Allow the file system to be mounted over an existing mount point, making the underlying file system inaccessible. If a mount is attempted on a pre-existing mount point without setting this flag, the mount will fail, producing the error "device busy". 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 con- tain executable files should always be mounted with the hard option. Applications using soft mounted filesys- tems 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 To improve NFS read performance, files and file attributes are cached. File modification times get updated whenever a write occurs. However, file access times may be temporarily out-of-date until the cache gets refreshed. 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 sets flush time to n seconds for both reg- ular 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), mkdir(2), mount(2), open(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 4.X used the biod maintenance procedure to perform parrallel read-ahead and write-behind on NFS clients. SunOS 5.X obsoleted biod with multi-threaded processing, which transparently performs parallel read-ahead and write-behind. SunOS 5.4 Last change: 3 Mar 1994