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Manual page for MOUNT(8)

mount, umount - mount and unmount file systems

SYNOPSIS

/usr/etc/mount [ -p ]
/usr/etc/mount -a [ fnv ] [ -t type ]
/usr/etc/mount [ -fnrv ] [ -t type ] [ -o options ] filesystem directory
/usr/etc/mount [ -vfn ] [ -o options ] filesystem | directory
/usr/etc/mount -d [ fnvr ] [ -o options ] RFS-resource | directory

/usr/etc/umount [ -t type ] [ -h host ]
/usr/etc/umount -a [ v ]
/usr/etc/umount [ -v ] filesystem|directory ...
/usr/etc/umount [ -d ] RFS-resource | directory

DESCRIPTION

mount attaches a named filesystem to the file system hierarchy at the pathname location directory, which must already exist. If directory has any contents prior to the mount operation, these remain hidden until the filesystem is once again unmounted. If filesystem is of the form host:pathname, it is assumed to be an NFS file system (type nfs).

umount unmounts a currently mounted file system, which can be specified either as a directory or a filesystem.

mount and umount maintain a table of mounted file systems in /etc/mtab, described in fstab.5 If invoked without an argument, mount displays the contents of this table. If invoked with either a filesystem or directory only, mount searches the file /etc/fstab for a matching entry, and mounts the file system indicated in that entry on the indicated directory.

mount also allows the creation of new, virtual file systems using loopback mounts. Loopback file systems provide access to existing files using alternate pathnames. Once a virtual file system is created, other file systems can be mounted within it without affecting the original file system. File systems that are subsequently mounted onto the original file system, however, are visible to the virtual file system, unless or until the corresponding mount point in the virtual file system is covered by a file system mounted there.

Recursive traversal of loopback mount points is not allowed; after the loopback mount of /tmp/newroot, the file /tmp/newroot/tmp/newroot does not contain yet another file system hierarchy. Rather, it appears just as /tmp/newroot did before the loopback mount was performed (say, as an empty directory).

The standard RC files first perform 4.2 mounts, then nfs mounts, during booting. On Sun386i systems, lo (loopback) mounts are performed just after 4.2 mounts. /etc/fstab files depending on alternate mount orders at boot time will fail to work as expected. Manual modification of /etc/rc.local will be needed to make such mount orders work.

See lofs.4s and fstab.5 for more information and WARNINGS about loopback mounts.

OPTIONS

mount

-p
Print the list of mounted file systems in a format suitable for use in /etc/fstab.
-a
All. Attempt to mount all the file systems described in /etc/fstab. If a type argument is specified with -t, mount all file systems of that type. Using -a, mount builds a dependency tree of mount points in /etc/fstab. mount will correctly mount these file systems regardless of their order in /etc/fstab (except loopback mounts; see WARNINGS below).
-f
Fake an /etc/mtab entry, but do not actually mount any file systems.
-n
Mount the file system without making an entry in /etc/mtab.
-v
Verbose. Display a message indicating each file system being mounted.
-t type
Specify a file system type. The accepted types are 4.2, nfs, rfs, lo, hsfs, and tmp. See fstab.5 for a description of 4.2, hsfs, and nfs; see lofs.4s for a description of lo; and see tmpfs.4 for a description of tmp. See [a manual with the abbreviation ADMIN] for details on rfs.
-r
Mount the specified file system read-only, even if the entry in /etc/fstab specifies that it is to be mounted read-write.

Physically write-protected and magnetic-tape file systems must be mounted read-only. Otherwise errors occur when the system attempts to update access times, even if no write operation is attempted.

-d
Mount an RFS file system. This option provides compatibility with the System V, Release 3 syntax for RFS mounts. Alternatively, the equivalent Sun syntax, -t rfs, may be used.
-o options
Specify file system options, a comma-separated list of words from the list below. Some options are valid for all file system types, while others apply to a specific type only.

options valid on all file systems:

rw|ro
Read/write or read-only.
suid|nosuid
Setuid execution allowed or disallowed.
grpid
Create files with BSD semantics for the propagation of the group ID. Under this option, files inherit the GID of the directory in which they are created, regardless of the directory's set-GID bit.
noauto
Do not mount this file system that is currently mounted read-only. If the file system is not currently mounted, an error results.
remount
If the file system is currently mounted, and if the entry in /etc/fstab specifies that it is to be mounted read-write or rw was specified along with remount, remount the file system making it read-write. If the entry in /etc/fstab specifies that it is to be mounted read-only and rw was not specified, the file system is not remounted. If the file system is currently mounted read-write, specifying ro along with remount results in an error. If the file system is not currently mounted, an error results.

The default is `rw,suid'.

options specific to 4.2 file systems:

quota|noquota
Usage limits are enforced, or are not enforced. The default is noquota.

options specific to nfs (NFS) file systems:

bg|fg
If the first attempt fails, retry in the background, or, in the foreground.
noquota
Prevent quota.1 from checking whether the user is over quota on this file system; if the file system has quotas enabled on the server, quotas will still be checked for operations on this file system.
retry=n
The number of times to retry the mount operation.
rsize=n
Set the read buffer size to n bytes.
wsize=n
Set the write buffer size to n bytes.
timeo=n
Set the NFS timeout to n tenths of a second.
retrans=n
The number of NFS retransmissions.
port=n
The server IP port number.
soft|hard
Return an error if the server does not respond, or continue the retry request until the server responds.
intr
Allow keyboard interrupts on hard mounts.
secure
Use a more secure protocol for NFS transactions.
posix
Request POSIX.1 semantics for the file system. Requires a mount version 2 mountd.8c on the server.
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.
nocto
Suppress fresh attributes when opening a file.
noac
Suppress attribute and name (lookup) caching.

Regular defaults are:

fg,retry=10000,timeo=7,retrans=3,port=NFS_PORT,hard,\
acregmin=3,acregmax=60,acdirmin=30,acdirmax=60

actimeo has no default; it sets acregmin, acregmax, acdirmin and acdirmax

Defaults for rsize and wsize are set internally by the system kernel.

options specific to rfs (RFS) file systems:

bg|fg
If the first attempt fails, retry in the background, or, in the foreground.
retry=n
The number of times to retry the mount operation.

Defaults are the same as for NFS.

options specific to hsfs (HSFS) file systems:

norrip
Disable processing of Rock Ridge extensions for the file system.

umount

-h host
Unmount all file systems listed in /etc/mtab that are remote-mounted from host.
-t type
Unmount all file systems listed in /etc/mtab that are of a given type.
-a
Unmount all file systems currently mounted (as listed in /etc/mtab).
-v
Verbose. Display a message indicating each file system being unmounted.
-d
Unmount an RFS file system. This option provides compatibility with the System V, Release 3 syntax for unmounting an RFS file system.

NFS FILESYSTEMS

Background vs. Foreground

Filesystems mounted with the bg option indicate that mount is to retry in the background if the server's mount daemon (mountd(8C)) 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.

Read-Write vs. Read-Only

File systems that are mounted rw (read-write) should use the hard option.

Interrupting Processes With Pending NFS Requests

The intr option allows keyboard interrupts to kill a process that is hung while waiting for a response on a hard-mounted file system.

Quotas

Quota checking on NFS file systems is performed by the server, not the client; if the file system has the quota option on the server, quota checking is performed for both local requests and NFS requests. When a user logs in, login.1 runs the quota.1 program to check whether the user is over their quota on any of the file systems mounted on the machine. This check is performed for NFS file systems by an RPC call to the rquotad.8c server on the machine from which the file system is mounted. This can be time-consuming, especially if the remote machine is down. If the noquota option is specified for an NFS file system, quota will not check whether the user is over their quota on that file system, which can speed up the process of logging in. This does not disable quota checking for operations on that file system; it merely disables reporting whether the user is over quota on that file system.

Secure Filesystems

The secure option must be given if the server requires secure mounting for the file system.

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.

SYSTEM V COMPATIBILITY

System V File-Creation Semantics

Ordinarily, when a file is created its GID is 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.2v and mkdir.2v Files created on file systems that are mounted with the grpid option will obey BSD semantics; that is, the GID is unconditionally inherited from that of the parent directory.

EXAMPLES

To mount a local disk:
mount /dev/xy0g /usr
To fake an entry for nd root:
mount -ft 4.2 /dev/nd0 /
To mount all 4.2 file systems:
mount -at 4.2
To mount a remote file system:
mount -t nfs serv:/usr/src /usr/src
To mount a remote file system:
mount serv:/usr/src /usr/src
To hard mount a remote file system:
mount -o hard serv:/usr/src /usr/src
To mount an RFS remote file system, retrying in the background on failure:
mount -d -o bg SRC /usr/src
To mount an RFS remote file system read-only:
mount -t rfs -r SRC /usr/src
To save current mount state:
mount -p > /etc/fstab

Note: this is not recommended when running the automounter, see automount.8

To loopback mount file systems:
mount -t lo /export/tmp/localhost /tmp
mount -t lo /export/var/localhost /var lo
mount -t lo /export/cluster/sun386.sunos4.0.1 /usr/cluster
mount -t lo /export/local/sun386 /usr/local

FILES

/etc/mtab
table of mounted file systems
/etc/fstab
table of file systems mounted at boot

WARNINGS

mount does not understand the mount order dependencies involved in loopback mounting. Loopback mounts may be dependent on two mounts having been previously performed, while nfs and 4.2 mounts are dependent only on a single previous mount. As a rule of thumb, place loopback mounts at the end of the /etc/fstab file. See lofs.4s for a complete description.

SEE ALSO

mkdir.2v mount.2v open.2v unmount.2v lofs.4s fstab.5 mtab.5 automount.8 mountd.8c nfsd.8

BUGS

Mounting file systems full of garbage crashes the system.

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.


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Created by unroff & hp-tools. © by Hans-Peter Bischof. All Rights Reserved (1997).

Last modified 21/April/97