mount_nfs(1M)
NAME
mount(nfs), umount(nfs) − mount and unmount an NFS file systems
SYNOPSIS
/usr/sbin/mount [−l] [−p|−v]
/usr/sbin/mount −a [−F nfs] [−eQ]
/usr/sbin/mount [−F nfs] [−eQrV] [−o specific_options] {host:path|directory}
/usr/sbin/mount [−F nfs] [−eQrV] [−o specific_options] host:path directory
/usr/sbin/umount −a [−F nfs] [−h host] [−v]
/usr/sbin/umount [−v] [−V] {host:path|directory}
DESCRIPTION
The mount command mounts file systems. Only a superuser can mount file systems. Other users can use mount to list mounted file systems.
The mount command attaches host:path to directory. host is a remote system, path is a directory on this remote system and directory is a directory on the local file tree. directory must already exist, be given as an absolute path name and will become the name of the root of the newly mounted file system. If either host:path or directory is omitted, mount attempts to determine the missing value from an entry in the /etc/fstab file. mount can be invoked on any removable file system, except /.
If mount is invoked without any arguments, it lists all of the mounted file systems from the file system mount table, /etc/mnttab.
The umount command unmounts mounted file systems. Only a superuser can unmount file systems.
Options (mount)
mount recognizes the following options:
−a Attempt to mount all file systems described in /etc/fstab. All optional fields in /etc/fstab must be included and supported. If −F nfs is specified, all NFS file systems in /etc/fstab are mounted. File systems are not necessarily mounted in the order listed in /etc/fstab.
−e Verbose mode. Write a message to standard output indicating which file system is being mounted.
−F nfs Specify the NFS file system type (see fstyp(1M)).
−l Limit actions to local file systems only.
−o specific_options
Specify options specific to the NFS file system type. specific_options is a list of comma separated suboptions and/or keyword/attribute pairs intended for the NFS specific module of the command.
The following specific_options are valid on NFS file systems.
defaults Use all default options. When given, this must be the only option specified.
rw Mount read-write (default).
ro Mount read-only.
suid Allow set-user-ID execution (default).
nosuid Do not allow set-user-ID execution.
Additional specific_options for the NFS file systems are listed under NETWORKING FEATURES below.
−p Report the list of mounted file systems in the /etc/fstab format.
−Q Prevent the display of error messages resulting from an attempt to mount already mounted file systems.
−r Mount the specified file system as read-only. This option is equivalent to the −o ro specific_option. Physically write-protected file systems must be mounted in this way or errors occur when access times are updated, whether or not any explicit write is attempted.
Options (umount)
umount recognizes the following options:
−a Attempt to unmount all file systems described in /etc/mnttab. All optional fields in /etc/mnttab must be included and supported. If −F nfs option is specified, all NFS file systems in /etc/mnttab are unmounted. File systems are not necessarily unmounted in the order listed in /etc/mnttab.
−F nfs Specify the NFS file system type (see fstyp(1M)).
−h host Unmount only those file systems listed in /etc/mnttab that are remote-mounted from host.
−v Verbose mode. Write a message to standard output indicating which file system is being unmounted.
−V Echo the completed command line, but performs no other action. The command line is generated by incorporating the user-specified options and other information derived from /etc/fstab. This option allows the user to verify the command line.
NETWORKING FEATURES
NFS
The following specific_options are applicable to NFS file systems:
acdirmax=n Hold cached attributes for no more than n seconds after directory update.
acdirmin=n Hold cached attributes for at least n seconds after directory update.
acregmax=n Hold cached attributes for no more than n seconds after file modification.
acregmin=n Hold cached attributes for at least n seconds after file modification.
actimeo=n Set minimum and maximum times for regular files and directories to n seconds.
bg If the first mount attempt fails, retry in the background.
devs Allow access to local devices (default).
fg Retry in foreground (default).
hard Once the file system is mounted, retry subsequent NFS requests until server responds (default).
intr Permit interrupts for hard mounts (default).
noac Suppress attribute and name (lookup) caching.
nocto Suppress fresh attributes when opening a file.
nodevs Deny access to local devices.
nointr Ignore interrupts for hard mounts.
port=n Set server UDP port number to n (the default is the port customarily used for NFS servers).
retrans=n Set number of NFS retransmissions to n (the default = 4).
retry=n Set number of mount failure retries to n (the default = 1).
rsize=n Set read buffer size to n bytes (the default is set by kernel).
soft Once the file system is mounted, return error if server does not respond.
timeo=n Set NFS timeout to n tenths of a second (the default = 7).
wsize=n Set write buffer size to n bytes (the default is set by kernel).
The regular defaults are:
acregmin=3 acregmax=60 acdirmin=30 acdirmax=60
actimeo has no default; it sets acregmin, acregmax, acdirmin, and acdirmax to the value specified.
bg causes mount to run in the background if the server’s mount daemon does not respond.
mount attempts each request retry=n times before giving up.
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 timeout is multiplied by 2 and the request is retransmitted. When retrans=n retransmissions have been sent with no reply, a soft mounted file system returns an error on the request and a hard mounted file system retries the request.
By default, the retry requests for a hard mounted file system can be interrupted. If the nointr option is specified, retry requests for a hard mounted file system are not interruptable which means that retry requests continue until successful. File systems that are mounted rw (read-write) should use the hard option.
The number of bytes in a read or write request can be set with the rsize and wsize options.
The devs option allows access to devices attached to the NFS client via device files located on the mounted NFS file system. The nodevs option denies access to devices attached to the NFS client by causing attempts to read or write to NFS device files to return an error.
File Attributes
The attribute cache retains file attributes for the client. Attributes for a file are assigned a time to be flushed. If the file is modified before the flush time, the flush time is extended by the time since the last modification (under the assumption that files that have changed recently are likely to change again 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.
DIAGNOSTICS
umount complains if the host:path is not mounted or if it is busy. The file system is busy if it contains an open file or some logged-in user’s working directory.
Cascaded distributed mounts (mounts whose mount point resides on another client node’s locally mounted disk) are not supported.
EXAMPLES
Mount a remote file system:
mount −F nfs serv:/usr/src /usr/src
Same as above:
mount serv:/usr/src /usr/src
Same as above but with a soft mount; the file system is mounted read-only:
mount −o soft,ro serv:/usr/src /usr/src
WARNINGS
A directory or file must be exported by the exportfs command before it is NFS-mounted (see exportfs(1M)).
Some degree of validation is done on the file system. However, it is generally unwise to mount file systems that are defective, corrupt, or of unknown origin.
AUTHOR
mount was developed by HP, AT&T, the University of California, Berkeley, and Sun Microsystems.
FILES
/etc/fstab Static information about the file systems
/etc/mnttab Mounted file system table
SEE ALSO
fsclean(1M), mount(1M), quotaon(1M), mount(2), fstab(4), mnttab(4), fs_wrapper(5), quota(5).
STANDARDS COMPLIANCE
mount: SVID3
umount: SVID3
Hewlett-Packard Company — HP-UX Release 10.20: July 1996